Half-Life 2: Being Gordon Freeman
by Mark Sivak

Half-Life 2a (HL2) offers a unique player experience through the use of design mechanics that give the player a feeling of absolute control. Branching off of the core idea of player control, the experience is further refined by how the HL2 gameplay is paced. The environment, enemies, and narrative all work together to create an experience filled with excitement, loneliness, intensity, nostalgia, and mystery. Please join me in an analysis of the ongoing adventures of Gordon Freeman.

Introduction

HL2 was released on November 16, 2004, and it is the sequel to the 1998 PC hit Half-Lifeb.  HL2 was originally released for the PC and has since been released to other platforms and bundled into the Orange Boxc. To date, HL2 has two sequel episodes of periodic content, Episode 1d and Episode 2e, with a third episode planned for release.  All the games in the Half-Life franchise are science-fiction (sci-fi) First Person Shooters (FPS).  The franchise was created by the Valve Corporation and they also developed HL2.  The game was originally published by Vivendi Universal Games but now is published by Valve and released through Valve’s online content delivery system Steam.  In the year of its release HL2 won over 35 “Game of the Year” awards.1  The game also has a Metacritic (average) score of 96 out of 100 making it one of the highest rated games of all time.2

In the original Half-Life, the game’s hero, Dr. Gordon Freeman (controlled by the player), inadvertently causes a disastrous “resonance cascade” at the Black Mesa research facility that opens a portal to Earth from a strange alien world called Xen.  At the conclusion of Half-Life Gordon Freeman attempts to close the portal between Xen and Earth by destroying the alien controlling it.  He is also properly introduced to the enigmatic G-man at the end of the original Half-Life, who becomes his elusive stalker throughout HL2. 

Half-Life 2 takes place several years after the events of the original game but the two games share many gameplay and narrative elements. The main antagonistic force that Gordon faces in HL2 is the Combine. The Combine are a collective of synthetic, alien, and human elements that have taken Orwellian, authoritarian control over earth after using the portal Gordon tried to close in the original Half-Life. Gordon must also face the hostile wildlife of Xen that were spread during the portal storm that Gordon caused at the end of the original game. Many of Gordon’s friends from the original game are also in HL2 including Isaac Kleiner, Barney Calhoun, Eli Vance, and Wallace Breen. Gordon is also joined by new friends including Alyx Vance, Dog, Judith Mossman, and the vortigaunts (an alien race).

This analysis of HL2 focuses on the unique design aspects and game mechanics that make HL2 one of the best games of all time. The terms sequence and encounter are used to discuss specific events or parts of the game, sequence usually refers to a longer gameplay segment while encounter refers to a specific fight or puzzle. The terms element, mechanic, and skill are all used to discuss a piece of the game design, environment, or the corresponding player action. The Design Notes section explains and defines the design elements and mechanics unique to HL2 and the Chapter Analysis gives a summary of how these are implemented for each chapter of the game.  The Chapter Analysis section contains plot information and puzzle solutions, this is your only spoiler warning.

Design Notes

Player control is a major design philosophy in both Half-Life and HL2.  From the beginning of HL2 the player has control of at least the camera for the rest of the game.  HL2 also has no formal cutscenes, objectives, or levels.  This design choice is much different from other sci-fi FPS series’ such as Haloa and Gears of War b that have definite levels with cutscenes using cinematic cameras and objectives either on screen or accessible through menus. It is this focus on player control that gives rise to many of the other unique aspects of HL2.

The levels in HL2 are called chapters. Chapters differ from levels because they usually begin and end in low pace areas instead of with formal or passive cutscenes. This makes the chapters in HL2 more seamless than other games. Instead of using formal cutscenes (also called passive cutscenes because they are a short movie sequence that the player cannot control) to advance the story and relay information to the player, HL2 has in-play cutscenes which are narrative scenes that unfold while the player can move around and interact with the environment.  Many games use in-play cutscenes for quick objective updates or as a break from the combat in conjunction with passive cutscenes.  Another example of a game that relies heavily on in-play cutscenes is the critically acclaimed BioShock e. By not changing the camera from Gordon Freeman’s (and the player’s) point of view and using exclusively in-play cutscenes, HL2 is restricted in terms of cinematic options, but the in-play cutscenes allow the game to never break the immersion between the player and Gordon. This trade off is advantageous to HL2 because the other player control mechanics build on top of in-play cutscenes and a non-moving first person camera. This choice is not necessarily a superior design choice because the emotionally charged, formal cutscenes of Gears of War have been shown to give players very high levels of engagement.3

The player’s chapter objectives are often revealed through in-play cutscenes but the environment in HL2 is also used to give the player gameplay information via cues.  These cues are expressed both visually and audibly to help the player progress through HL2. 

While visual cues are used much less than audio cues in HL2, they are still important for giving information to the player.  From the first chapter, the player sees the response of the Combine’s technology if their indicator lights are red or green.  This is used on doors, cameras, turrets, hoppers, and switches.  Also some areas have lighting or coloring to draw the players attention or give them a hint of their objectives.  There is a special form of visual cue in HL2 called a vista.  Vistas are areas which are meant to give the player an expressive view of the environment around them.d1  Because the camera never shifts from the first person view of Gordon, vistas are used as cinematic devices that show scale or give depth to the player’s actions in their environment, making up for the main disadvantage of in-play cutscenes. Vistas are also used to control the player’s pace, giving them a pause from the action and acting as a break point between chapters.

Audio cues in HL2 are very important to the gameplay experience. Michael Sweet of Audio Brain Inc. stated about game audio, “Whether you’re struggling to make it to the end of a level or waiting for the next monster to appear from around the corner, the music and sound can make the player’s heart race or stomach drop.”4 The HL2 heads-up display does not contain radar or another mapping mechanic. Because of this the audio of game is used by the player to understand the environment around them. Every non-playable character, (NPC) friend and foe, in HL2 has a distinct sound.  NPC sounds are used to convey information to the player and also to build up suspense and control the player’s pace. Because enemies make unique sounds the player knows that what enemies are lurking near them.  Besides the NPC sound cues, HL2 also has environment and equipment sound cues.  Interactions with switches, vehicles, crates, barrels, and doors have unique sounds that the player can retrieve information from like the switch is active or door is locked.  Also the music in HL2 ranges from heart pumping musical bursts that signify intense fast paced sequences to long lonely musical tracks that coordinate with puzzle and narrative sequences. The soundtrack also utilizes environment and NPC sound effects to add to the audio experience of the player.5

Player control is also expressed in the level design of HL2.  The player has a sense of freedom and they can explore the world at their own pace.  This feeling is produced by using two design elements that herd the player around the game world.  These design elements are called gates and arenas.

The player is usually kept in an in-play cutscene area or combat area by use of a gate. A gate is an environmental entity which is defined by the Valve developers in the developer commentary of Half-Life 2: Lost Coast h (Lost Coast).h1 There are three different kinds of gates used in HL2: soft, hard, and story.  A soft gate is a simple task that the player must overcome in order to continue forward in the experience.  These gates are usually used for training of hard gates or to control the player’s pace.  Hard gates include a puzzle the player must solve to continue.  Hard gates include multiple step switches, navigation, and physics puzzles.  Story gates require an event outside the players control to open. Story gates include locked doors opened by NPCs, explosions, and teleportation. Each type of gate controls the player’s pace and they are also an essential element of arenas.

The term arena also comes from Valve developers and a definition can be heard in the developer commentary of the Lost Coast.h2  Arenas are areas that have multiple entry points for enemies as well as a gate that restricts the player from moving on until they complete the challenge within the arena.  Arenas also have a one-way gate at their entrance so the player can not retreat. In HL2 many of the encounters that could be considered classic “boss” fights take place within arenas.

The environment design and incorporation of gates and arenas leads to two forms of gameplay: combat and puzzles.  Both of these types of gameplay require equipment like the Hazardous Environment Suit (HEV Suit), the Zero-point Energy Field Manipulator (Gravity Gun), and the infamous crowbar.  Of course both combat and puzzles can be very dangerous so HL2 has a system to give the player ammo, health, and energy.  This system is called Dynamic Resupply and the cornerstone of this system is the Item Crate.e1

The HEV Suit is another hold over from the original Half-Life game.  When Gordon does not have the HEV Suit on, the HL2 heads-up display (HUD) is invisible.  Besides showing the HUD, the HEV suit also adds some specific gameplay mechanics, notably the flashlight, underwater breathing, sprinting, and anti-venom.  The flashlight, underwater breathing, and sprinting are used in both combat and puzzles. All three draw from the same power source within the suit that when depleted must take time to recharge, this is important because it means the player must use their mechanics sparingly and their pace is controlled by the limited duration they can be active between recharge times.  Anti-venom has a very specific use when fighting poisoned headcrabs, they are discussed further in the analysis of Chapter 6.  The poisoned headcrabs can lower Gordon’s health to 1 and then the suit releases anti-venom to raise his health back to a safer level. This is also used to control the player’s pace because the player needs to stay in a relatively safe area to wait for Gordon’s health to return.

The crowbar is the first weapon that Gordon can use and it also has deep roots from the original Half-Life game.  It is used to interact with the environment and is also used for combat.  Objects in the world like locks, item crates, wooden boards, and debris can easily be cleared by using the crowbar.  Most soft gates can be cleared by using the crowbar, so it is a key tool to control the players pace. However, while the player has the crowbar equipped they are somewhat defenseless, especially from ranged attacks.  Paired with many of the audio cues, this gives the player an anxious feeling when they find situations that require them to put away their conventional weapons and pull out the crowbar. This effect on the player is much like the flashlight mechanic of Doom 3j. In Doom 3 the player is forced to put themselves at risk to use the flashlight because they cannot have a weapon and the flashlight equipped at the same time.

The Gravity Gun is the most important weapon that Gordon wields and it also showcases the physics of HL2.  The gravity gun is used to solve many physics based puzzles and also used to pass soft and hard gates.  The gravity gun has the same effect on the player as the crowbar in that while the player can use the gravity gun as a weapon it is usually not as effective as conventional weaponry. So when using it they are at a disadvantage.  However, late in the game, the gravity gun becomes a weapon all its own (discussed in the analysis of Chapter 12).  The various locales that Gordon must traverse throughout HL2 are littered with items that can be manipulated by the player using either the Gravity Gun or the use button.  The majority of these items are barrels and crates.  The other types of physics items can be used as projectiles with the Gravity Gun including saw blades and gas tanks, which becomes an important mechanic when ammo is scarce.

Valve decided to have a specific model for a crate that holds ammo, energy, and health items called the Item Crate.  The obvious use of these is for the player to replenish their health and supplies throughout the game.  In HL2 they are also used to trick or lure the player into moving to certain areas. They also force the use of the crowbar because that is the easiest way to destroy the crates and get the items they hold. Because the player must destroy the crates to see their contents, the crates are also used a pacing tool much like a soft gate.

All of the various design elements and mechanics are used to influence the player while still giving them the feeling of control.  The player is further controlled by using puzzles that limit the pace the player can progress through the game and force them to think about the game world around them.  The puzzles require teaching of skills and mechanics so that the player can complete them without becoming frustrated or just guessing.  Because many of these puzzles are hard gates they also control the pace of the player. Everything in HL2 affects the player’s pace. The pace has a direct effect on the interest and enjoyment of the player. The connections between teaching and puzzles, and pace and interest are discussed in the following sections.

Teaching and Puzzles

As stated in the previous section, the two main gameplay types of HL2 are puzzles and combat. Teaching the player skills to complete puzzles and use game mechanics is very important because objectives are conveyed to the player through cues, NPCs, and the environment.  A player’s working or short-term memory is used to learn these skills. A person can keep 7±2 “chunks” of information in their working memory.6 The term “chunks” refers to a method used to take a complicated piece of information and separate it out into simpler “chunks” in working memory, a method called “chunking”.7 This idea of “chunking” is demonstrated throughout HL2 in how the puzzles are presented to the player. Also, because the information for these puzzles is kept in working memory, cues are often used to remind the player what they have learned, a process called “maintenance rehearsal”.7 In HL2 this process is called a mechanic refresher.e2

There are three main types of puzzle elements in HL2: platforming, physics, and combat. Most of the puzzles in HL2 use more than one of these elements as well as simple elements like switches and valves. Platforming elements include tasks like jumping, sprinting, and using the flashlight. Physics puzzle elements require using objects in the world to complete a task that requires the use of the objects weight and physics. Physics puzzles are designed into almost all the other chapters in HL2 and are more frequent after the player gets the gravity gun. Combat puzzle elements usually include enemies that require a specific skill to defeat through combat including rolling grenades into floor turret or weaving rockets around a gunship’s machine gun fire. The puzzles in HL2 increase in difficulty so that the player is constantly having to use skills they have learned with new skills they are being taught.

A teaching cycle is used in HL2 to teach the player new skills for solving puzzles.  It is important that the players learn by doing as this is the most effective way to teach players new skills.3 This cycle applies to all players regardless of skill and experience. For many of the basic skills (navigation, flashlight, and sprint) this cycle is not used, but for many of the advanced skills (gravity gun) or puzzles (physics and combat) this cycle is vital. Figure 1 shows the phases involved in the cycle and the level of enjoyment the player gets from each phase.

The duration of each phase of the cycle depends on the skill the player is learning, some phases last entire chapters while others are over in a few seconds. The first phase in the teaching cycle is that the player is introduced to the skill.  This is usually done by cues or told to the player through an in-play cutscene.  The player is curious about how to use the skill so their anticipation leads to a medium level of enjoyment.  The second step of the cycle is the learning phase.  In this phase the player is given a very simple and obvious use of the skill that was just introduced to them.  This is not challenging to the player and therefore has a lower enjoyment level.  Testing is the third step of the learning cycle.  This is a harder use of the skill than was first presented and because of this increase in difficulty it has a higher enjoyment level.  The next step is the most important of the cycle, the challenge.  In this step the player needs to use their knowledge of the skill to extend its use beyond the obvious uses shown to them previously.  The challenge phase of the cycle has the highest level of enjoyment because if the player succeeds they have mastered the skill.  The final phase of the cycle is reuse.  Many puzzles and mechanics are recycled throughout HL2 and while the player derives some enjoyment from accessing the skill necessary to complete the challenge, it does not have the same level of enjoyment as the challenge phase.

This teaching cycle is not exclusive to HL2, but many of the best examples can be found in this game. In the Chapter Analysis section, the different types of puzzles are discussed as well as how they impact narrative, pace, and enjoyment of the experience.

Pace and Interest

Many FPS game experiences are compared to riding a roller coaster. They have hills, drops, sudden turns, and loops for heart-pounding exhilaration and action. The HL2 experience includes all of these elements but because of the player freedom in how they move through the game, the overall experience is closer to that of a haunted or fun house attraction rather than a roller coaster. In HL2, through use of gates and arenas the player’s pace is controlled, much like the hallways and rooms of a haunted house. Haunted or fun house experiences are also controlled by distance rather than time, much like the environments of the original Half-Life and HL2.8 In HL2 most of the enemy artificial intelligence is unscripted, meaning that the player’s actions force the enemies to react, thus creating a different experience depending on player choices. Haunted houses usually also have this quality because the actors in a haunted house react differently to the guests they are trying to scare. Also, with no passive cutscenes, there is a chance that a player will miss or not understand an event like someone turning away from a vital part of a haunted house, closing their eyes, or even skipping a room. HL2 also focuses more on exploration by the player, allowing them to walk into traps instead of leading them or pushing them like a roller coaster on a rail. All of these similarities between haunted or fun house attractions and HL2 have to do with pace and interest.

The interest level of an experience can be expressed by using an interest curve. Jesse Schell explains interest curves and how the level of interest impacts an experience in his book “The Art of Game Design”.9 Drew Davidson discussed the relationship between immersion and investment at the 2008 Games + Learning + Society Conference.10 A sample interest curve made for use in this analysis for HL2 is shown in figure 2.

Interest curves have three distinct parts: the hook, lesser trials, and major trial. The hook is the first part of the experience that grabs the audience or player and draws them in, immersing them into the experience. The lesser trials follow the hook and fluctuate in interest on a steady rise towards the third part of the curve, the major trial. During the lesser trials the immersion of the experience also grows as they invest in the experience. The major trial is the big finish, the final quest, the climax. The player is completely immersed and invested in the experience. They will complete the game no matter what. Not every game or experience follows an interest curve completely but many of the best games like HL2 follow an interest pattern that includes the three parts as well as the relationship between immersion and investment.

Schell also does an excellent job of explaining pace (which he refers to as flow, a psychological concept that refers to a person’s state of mind and was proposed by Mihály Csíkszentmihályi11). 12 In this analysis pace and flow can be considered an equivalent term under the definition of pace that follows. If the pace of the game is fast or high for too long the player will get fatigued or frustrated and lose interest. If the pace of the game is too low the player will get bored and lose interest. Change and surprise are very important for pace because the pace needs to shift in order for the player to have an optimum level of interest. Changing the pace needs to match the changes in the narrative and also the level of interest. Players with higher interest will endure longer periods of high or low pace because of the investment they already have in the gameplay experience. Surprises also need to match the narrative so that they do not jar the player out of their immersion. Also it is important to surprise the player in a fair way so that they do not feel frustrated at the game mechanics.g Pace should not be confused with intensity. A low pace sequence can have very high intensity. An example being some of the trap encounters in Chapter 6 of HL2 (discussed further in the Chapter 6 analysis). Intensity is usually associated with failure states for the player. If the threat of failure is high usually the intensity is also high.

The player freedom and control in HL2 leads to a haunted or fun house type experience where the pace the player chooses directly relates to their level of interest. While the story has an effect on the experience of HL2 the pace does more to dictate the player’s level of interest, immersion, and investment.

Chapter Analysis

HL2 is made up of 13 Chapters and 1 sub Chapter (9a).  The chapters almost always begin and end during low pace sequences or in-play cutscenes and they can be separated into three categories: narrative, vehicle, and combat chapters.  Narrative chapters are mostly used to advance the story. They are heavy on in-play cutscenes and light on everything else.  The narrative chapters of HL2 are Chapters 1, 2, 5, 9a, and 13.  The scout car and the airboat are the two vehicles usable by the player in HL2.  The Airboat is used almost exclusively in Chapter 4 and the Scout car is used mostly in Chapter 7, these chapters are vehicle chapters.  Combat chapters make up the rest of the game, as the name implies the majority of the time spent playing these chapters is in combat.  These chapters can also have puzzles, in-play cutscenes, and minor vehicle gameplay.  The combat chapters of HL2 are Chapters 3, 6, 8, 9, 10, 11, and 12.

The hook of HL2 is the first and second chapter. However, an argument could be made that the hook extends until Chapter 5, when the player gets much of the story and also the gravity gun. The lesser trials consist of all the chapters from the hook (either starting at Chapter 3 or 6) up until the major trial which begins in
Chapter 12.

Throughout this chapter analysis, Gordon and the player are mentioned independently in the mechanics, puzzles, and pacing analysis of the individual chapters.  The player is mentioned when discussing gameplay mechanics and Gordon is noted when the story or pace of a chapter is discussed.  Within the context of the game, these two entities are one and the same, but the transition between them can
be confusing.

Chapter 1: Point Insertion

The first chapter in HL2 is used to setup the environment (City 17) and narrative as well as teach the player about basic movement and interaction.  Once the G-man finishes his speech about Gordon being “the right man at the wrong time” at the very beginning of the game, control is pushed to the player. The G-man is a mysterious character in a suit with a briefcase. The G-man can be seen throughout the original Half-Life in Black Mesa and on screens and off in the distance, often in lower paced gameplay sequences of HL2. The G-man is an important character because he signifies loss of player control. The G-man can teleport Gordon, get to inaccessible places, and freeze time. Because he follows the player throughout HL2 he gives the player a sense of unease like they are being watched or influenced by powers outside their control.

All of the puzzles in Point Insertion have to do with navigation around the game world and interacting with it.  Most of the puzzles do not follow the teaching cycle because they are basic and because these skills will be used in conjunction with other skills later on during platforming puzzles.  The main mechanics learned in this chapter are basic movement, crouching, ladders, opening doors, jumping, and manipulating objects. There are no weapons in this chapter and Gordon does not yet have his HEV suit.

One of the most memorable puzzles in this chapter is when an Overwatch Metro Cop knocks over a can and forces Gordon to pick it up and put it in the trash can.  The Metro Cops are humanoid Combine troops that are stationed in urban areas. Once the player picks up the can a tooltip appears on the screen stating that Gordon can toss objects.  Timed correctly, this appears just in time for the player to click the throw button and hit the Cop, who is not pleased with Gordon’s disobedience and attacks him.  Point Insertion is light on puzzles and teaching because it is the first chapter and so the narrative introduction of the world can be the main focus for the player.

The short speeches of the citizens in this chapter about memory erasure, reproductive suppression fields, and instinct vs. immortality are used to give the player a sense of uneasiness about City 17 and about the Combine.  When Barney and Dr. Kleiner are reintroduced it is used to show that there is a force at work against the Combine and that they survived the events of Black Mesa in the
original Half-Life. 

The pace level of the chapter through the train station is low but once outside the player is presented with increasing danger.  Combine troops and citizens litter the streets and there are also Scanners patrolling the area. These flying robots take pictures of Gordon to alert the Combine to his presence and also can temporarily blind him with their camera flash. While scanners alone are mostly an annoyance, the blinding flash can become a pressing issue for the player when platforming or in a large-scale battle. This simple change and the ability for scanners to alert other Combine to Gordon’s location can lead the player to reevaluate the threat
scanners pose.

Without a weapon, the player’s only defense is to flee. This makes the roof chase important for pace because under normal circumstances the player could stop and eliminate the foes.  The ending to the chase and this chapter is Alyx Vance saving Gordon.  This event is important to the story of HL2 because it is the first time the player meets Alyx, his most important ally and possible love interest, and she shows that she can handle herself in a fight, and that she cares for Gordon’s well being, two narrative ideas that reinforced throughout the game.

The first chapter of HL2 focuses on story and game world navigation. The player is introduced to the G-man, Barney, Dr. Kleiner, Alyx, Wallace Breen, and the Overwatch. The chapter also introduces the setting of City 17 and sets up the relationship between the resistance and the Combine. The pace of the first chapter spikes during the meeting with Barney and the chase through the city, but overall is low pace introduction to the game.

Chapter 2: “A Red Letter Day”

The second chapter of HL2 has more narrative information than the first.  This is because the player needs to focus on learning to navigate and interact with the world in the first chapter.  “A Red Letter Day” is a series of reunions. Gordon is reunited with allies, enemies, and classic equipment in this narrative chapter. There are puzzles and skills that the player must complete and learn in this chapter and they focus on basic combat and the HEV suit.

Upon reaching Dr. Kleiner’s lab through a series of secret passages Gordon is reunited with Barney and Dr. Kleiner himself.  Having the lab feel safe to the player by using the secret passages is very important because the player needs to focus on the story heavy dialogue and get used to in-play cutscenes instead of checking all windows and doors for zombies.  Gordon is also reunited with his HEV suit which he wears for the rest of the game. After donning the suit the player learns how to power the suit using the wall mounted Combine battery unit.  By introducing this mechanic with no pressure the next time a player encounters a battery unit they will know how to use it even if they are in the middle combat or a puzzle. 

The teleportation to Black Mesa East in-play cutscene in this chapter is one of the only times in the game when the player cannot move. This cutscene has many parallels to the reactor cutscene at the beginning of the original Half-Life such as a mechanical failure that results in random teleportation. During this in-play cutscene Gordon is reunited with Wallace Breen, the main antagonist of HL2 and the past administrator of Black Mesa. At the end of this chapter Gordon is reunited with his last piece of important equipment from the original game, the crowbar.

“A Red Letter Day” is the second narrative chapter of HL2 and is used to reunite the player with equipment and characters from the original Half-Life. Also Gordon is revealed to the main antagonist, Wallace Breen through a mechanical failure much like the “resonance cascade” event also from the original Half Life. The pace of this chapter remains slow while the main in-play cutscene unfolds, at the end of the chapter the pace increases due to the botched teleportation.

Chapter 3: Route Kanal

Route Kanal is the first combat chapter in HL2. The player starts with the crowbar as their only weapon and this is the first chapter to use the sprint and flashlight mechanics of the HEV suit. The other weapons acquired in this level are the pistol, sub machine gun (SMG), gun turret, and grenade. The player also learns to swim and solve physics puzzles in this chapter as well as deal with barnacles, manhacks, headcrabs, and zombies. Headcrabs and zombies are discussed in the Chapter 6 analysis.

After the lock puzzle that is a soft gate solved by the crowbar and the opportunity to destroy some of the scanners, the crowbar must be used on two Overwatch Metro Cops. These Cops drop a pistol, the first projectile weapon the player gets to use in HL2 and there are plenty of uses for it throughout the chapter. Overwatch Metro Cops appear in areas that the player cannot reach so the pistol must be used to defeat them. Also explosive barrels (barrels that explode when shot) are introduced in this chapter and must be used to get by a soft gate. The barrel mechanic follows the teaching cycle with first the gate puzzle and then later in the chapter when the player can use the barrels to kill Metro Cops to save ammo for the pistol.

Since the player was only told in the last chapter that they need to make their way to Black Mesa East the player needs to be updated on their objectives so that they do not get confused or frustrated with their progress. This is done by a series of checkpoints manned by citizens and vortigaunts friendly to Gordon. These checkpoints are also used to adjust the pace of the chapter and break up the more intense combat sequences.

Route Kanal also has the first physics puzzle of HL2, a physics seesaw. The term seesaw comes from the playground ride comprised of a long board supported in the middle and the angle of the board can be manipulated by adding weight to either side of the seesaw. This first physics seesaw serves as the tutorial for all the physics puzzles in HL2 because the player has to move environment items onto the seesaw in order to progress forward.

Barnacles are very interesting enemies that the player faces for the first time in this chapter. They were also present in the original Half-Life. Barnacles are introduced using a classic teaching method from the original Half-Life and HL2, a crow is startled by the player and then flies into the branacle’s tongue and it brought up the barnacle’s waiting maw.8 By using an NPC to show a new enemy mechanic, the player gets to see the mechanic in a low intensity way and the interaction of two entities in the environment gives depth to the world, making it feel more real to the player and increasing immersion. As the name suggests these monsters clamp onto the ceiling and release a tongue-like appendage that picks up anything it touches so the barnacle above can devour it. The barnacle mechanic is simple but because they are indiscriminate in what they eat, they can be used to eat other foes, explosive barrels, or used by the player to reach higher areas.

Metro Cops can release manhacks (small flying robots) which use their rotating blades to attack from a very short range. Because manhacks do not drop ammo or any other items, they present the player with an interesting choice: destroy them from a safe distance with a gun and use up ammo or from close range with a well timed crowbar hit. Later in HL2 the player can use the gravity gun to dispatch manhacks and so the choice to conserve ammo becomes less important if the player has mastered the gravity gun mechanics.

The first combat chapter of HL2 introduces the pistol and crowbar as well as explosive barrels. This chapter breaks the slow pace of the first two chapters with combat sequences that have little or no game narrative. Also the resistance checkpoints and puzzles that the player finds in Route Kanal cause fluctuations in the pace and keep the player interested in the limited narrative that is introduced in this chapter.

Chapter 4: Water Hazard

In this chapter the player must use the airboat, making Water Hazard the first vehicle chapter of HL2. The gates in this chapter are more obvious than other chapters because they force the player off the airboat and into conventional combat situations. Also there is a chopper (Combine combat helicopter) that harasses the player throughout the chapter is used to urge the player forward instead of allowing the player to explore.

While the airboat mechanics give the player a different experience, the same puzzle types and gates are used on the airboat. There are platforming puzzles for the airboat including using ramps for jumps and skimming from canal to canal. Without changing the barnacle attack mechanic, the player has a wildly different experience with barnacles on the airboat. While on the airboat, the barnacles tongue will pull Gordon out of the boat completely, forcing the player to kill the barnacle to return to the airboat and continue.

The player is forced off the airboat several times in this chapter by hard gates like boat lock doors and physical gates, which changes the pace and breaks up the airboat mechanics with combat mechanics the player learned in the last chapter. There is also another physics puzzle in this level that requires use of the gravity gun once the player is forced off the airboat. Many of the puzzles in this chapter are reflected in Chapter 7 when the player uses the scout car and in other chapters that require more advanced use of the gravity gun.

Water Hazard is also the first chapter that has an arena with a boss fight. The player is chased by a chopper throughout this chapter, a design technique that shows the player their objective early to build suspense and also foreshadow the upcoming battle.d2 Besides forcing the player forward, it also assures the player that they are going in the right direction. The player is shown how to damage the chopper earlier in the chapter by learning how to use the weapon that gets mounted on the airboat. Upon entering the arena, the player is comfortable with the method of destroying the chopper because they have previously learned it. The mines that the chopper drops add a platforming element to the fight as well as a higher level of interest because the player must look up to fight the chopper and then down to avoid the mines. As with many arenas there is a very low paced sequence after the arena so that the player does not get fatigued.

Water Hazard is the first vehicle chapter of HL2. In this chapter the player must use the airboat to navigate the canals in hopes of reaching Black Mesa East. The pace throughout the chapter swings between encounters on foot, airboat sequences, and chopper chases. The next chapter is a narrative chapter so that gives the player time to recover from the chopper boss battle in the arena at the conclusion of this chapter.

Chapter 5: Black Mesa East

Black Mesa East is a narrative chapter and its main focus is the gravity gun tutorial. Before the tutorial begins, the player is given some time to wander the facility and talk with various characters like Dr. Eli Vance and Dr. Judith Mossman. Like the second chapter, the player feels safe in Black Mesa East, this is done once again to allow the player to watch the in-play cutscenes instead of running from door to door looking for Overwatch. Besides teaching the player the gravity gun mechanics, this tutorial is used as the introduction of Dog, the large pieced-together robotic guardian of Alyx, and to show more of Alyx’s personality like her dislike of Dr. Mossman.

This is the shortest chapter in the game depending on the time the player needs to complete the tutorial. Because the gravity gun is so vital and is used for the rest of HL2, this chapter could be considered the end of the game’s tutorial or hook. All the skills used before now including weapons, driving, and platforming are all used in the rest of the game. Valve considers it vital to continue teaching the player throughout their games, but at the end of Black Mesa East all the major skills have been learned.8

The pace of this chapter is slow until the Combine attack at the end. Some of the activities the player does during the gravity gun tutorial with Dog can spike the pace, but overall this chapter feels like it has a low pace because of the fast pace of Chapter 4.

Chapter 6: “We don’t go to Ravenholm”

“We don’t go to Ravenholm” is the most unique chapter in HL2. Many players remember this chapter because it has a completely different pace and feel than the previous chapters. This is a horror and suspense themed chapter that would fit well in any survival horror game.  This horror atmosphere is created by claustrophobic environments, use of darkness, and building suspense through audio cues. All the types of headcrabs and zombies flood Ravenholm and there are no Combine units.   This is a much slower paced level because of the low amount of ammo and the traps that can be used to kill the headcrabs and zombies.  After receiving the gravity gun in chapter 5, this chapter forces the player to use it in new ways like a drawn out challenge phase of the teaching cycle.

Gordon had to fight headcrabs and zombies in the original Half-Life. Headcrabs’ mechanics are a lot like those of manhacks. Headcrabs must attack from short range and they drop nothing when defeated, presenting the same ammo dilemma as manhacks. Headcrabs attach to the head of humans and turn them into zombies, a habit that gives them their name. Normal zombies move slowly and either attack with their claws or by throwing objects at the player. Besides the normal types of zombies and headcrabs there are two new types of each in HL2: fast and poison.

The fast headcrabs have longer legs and as their name suggests they can move faster than normal headcrabs. Besides their speed, look, and sound their attack mechanics are the same as the normal headcrab. Fast headcrabs make fast zombies which can run on all fours, leap great distances, climb buildings, and attack with much more aggression than normal zombies. Fast zombies must be fought at high pace because of their attack speed and their chilling howl. The fast zombie sound cues allow the player to know they are coming, thereby creating suspense.

The poison headcrab is black and has a sound akin to a rattle snake. They can poison the player, reducing Gordon’s health to 1 and forcing the HEV suit to automatically cure him. This affects the pace of the experience for the player because once poisoned they must stay in relative safety until the suit can sufficiently heal Gordon. The poison zombie is slow moving but can throw poison headcrabs at the player. Poison zombies take the most damage of any zombie type making them a priority to kill to avoid poisoning Gordon. By varying the kinds of headcrabs and zombies, the player is faced with similar foes that require different skills to defeat.

To break up the horror atmosphere in this chapter there is a helper character named Father Gregori who helps the player by giving Gordon the shotgun and showing him the correct route to get out of Ravenholm. Father Gregori is a loud and humorous character that offsets the mood of this chapter while giving the player narrative and objective information.

The lack of ammo throughout Ravenholm forces the player to find creative ways to kill the zombies and headcrabs that infest the area. The gravity gun can be used to throw saw blades, meat hooks, and explosives with lethal results. There are also traps that Father Gregori has setup that are a special kind of gate. These traps include spinning blades, electrified fences, and combustible propane gas. The traps are introduced to the player using the teaching cycle and because Valve likes to surprise the player there is a trap that backfires. Gordon can crouch next to spinning blade traps and turn them on, once the zombies and headcrabs hear the trap they come to attack the player and get splattered. In an area with a hard gate there is a spinning blade that breaks and if Gordon is crouched beneath it he gets badly damaged or killed. This causes the player not to trust the traps and adds depth to the world by showing a different result than expected.

This chapter’s theme is very strong and is amplified by the intimate atmosphere the player traverses with Father Gregori as well as the traps they must use. The unique elements in this chapter lead to a unique pace. The slower paced gravity gun and trap sequences are broken up by encounters with fast zombies and Father Gregori, but overall the pace of the chapter is low but intense. The intensity of the chapter is important because just as long stretches of the same pace gameplay can fatigue the player so long stretches of the same intensity.

Chapter 7: Highway 17

The scout car is the main focus of Highway 17 and it shares many of the puzzles and mechanics as the airboat in Chapter 4. After the slow pace and enclosed feeling of the previous chapter the player needs a different experience to avoid fatigue.  The open roads of Highway 17 are that different experience. Antlions, large insect-like monsters, are introduced in this chapter and with them there are several new mechanics that the player must learn. There are also three Combine Gunships in this chapter and the rocket propelled grenade (RPG) that must be used to destroy them.

The scout car has three unique mechanics that the airboat does not. The first is that the scout car can be flipped over and the player is required to use the gravity gun to right the vehicle before they can continue. The second is that the scout car has a mounted weapon for the entire chapter. The last unique mechanic is that the scout car can get a boost in speed to go over jumps and solve platforming
puzzle elements.

Antlions are not part of the Combine and will attack Combine units. In this chapter there is an endless supply of antlions if the player disturbs the sand. Antlions are only dangerous in swarms, which makes the thumper mechanics very important in this chapter. Thumpers are mechanical pistons that vibrate the sand which forces the antlions to stay away. Because of this mechanic thumpers become platforming puzzles, the player can move from thumper to thumper in relative safety or turn them off and allow the antlions to devour any Combine close by. Thumpers are also used to affect pace because they are placed in useful areas that the player should stop to explore.

One of the most interesting platforming puzzles in HL2 is in this chapter. There is a bridge that Gordon must traverse to turn off the suppression shields and continue. The player must walk on narrow supports or jump to ruined catwalks. The interesting part of this puzzle is the return trip after Gordon cuts the power. He must go back across the bridge while under fire from a Combine Gunship. Gunships are synthetic flying enemies that must be destroyed using explosives like the RPG. However because the player has already crossed the bridge once in the testing phase of teaching cycle they are now challenged with going back across the bridge under much higher stress.

The pace of this chapter is much like the pace of Chapter 4. After the slow crawl through Ravenholm in Chapter 6 the open roads and fast paced antlions are a welcome change for the player. The pace of this chapter shifts between on foot sequences and sequences in the scout car, much like the first vehicle chapter. The inclusion of this second vehicle chapter is important because the chapters before and after this chapter are slow crawls. Also physical distance needs to be crossed by the player so that the narrative of HL2 is believable.

Chapter 8: Sand Traps

This chapter begins with the player still on the roads using the scout car. Unlike the airboat, which is only used in chapter 4 the scout car is used in chapter 7 and in this chapter, Sand Traps.  The scout car gameplay ends in this chapter with a very fast paced sequence of dropship combat and Overwatch troops attacking Gordon and resistance troops in an arena created with 3 buildings, a lighthouse, and cliffs. After the gunship battle on the top of the lighthouse Gordon must navigate the cliff path allowing the player’s pace to slow for the teaching of the main mechanic of this chapter, the antlion sand traps.

This chapter gets its name from the sandy areas that Gordon must avoid in order to not summon the antlions out of the ground, this is an example of a platform puzzle. The sand trap mechanic perfectly follows the teaching cycle. The mechanic is introduced by two friendly NPCs who act out a short in-play cutscene. After simple jumps which correspond to the teaching phase the player is forced to use the gravity gun to move objects for a testing phase of the mechanic. The challenge phase comes from the optional item crates which are off the main path but clearly visible to the player. This mechanic is also reused throughout the rest of this chapter.

The sand traps offer an interesting game pace choice because if the player is very careful in not touching the sand they can avoid fighting any antlions.  If the player is not careful or simply does not care they can end up neck deep in antlions and the pace is completely different because then the player spends their time guns blazing.  The player can use either strategy to complete the level if they can overcome the onslaught of antlions caused by not avoiding the sand traps.

There is an arena with a boss fight in this level that is used to up change the presumably slow pace of the sand traps. The boss is an antlion guard, a large creature that can charge the player and also “kick” debris at them to cause damage. The antlion guard is also used as a narrative tool for another very unique weapon and mechanic, the pherapod. The pherapod (usually called bugbait) is a softball sized gland of the antlion guard that can used to control the normal antlions. Once the player receives the bugbait they are given an in-play cutscene and tutorial on its use like many of the other mechanics in HL2.

Controlling the antlions is a very interesting mechanic because now the player has learned all their disadvantages (cannot go near thumpers) and advantages (there is an unlimited supply of them). The player must now disable thumpers and force antlions into suicidal or very dangerous battles without worry because another will take the place of any that die.

The changes in pace force the player to think more about what is in the next room than where they are in the overall story, because of this, foreshadowing is used to constantly remind the player of where they are in the narrative. Since the end of Chapter 6 Gordon objective has been to try to reach the prison, Nova Prospekt, and to try to rescue Eli Vance. This chapter ends with Gordon besieging the prison with a horde of antlions which is the setup for the next two chapters that take place inside Nova Prospekt.

The focus of Sand Traps is on the antlions and their mechanics. The pace changes quickly from the scout car sequences to the lonely and (hopefully) quiet platforming sequences involving the sand traps. The arena battle against the antlion guard is used to spike the pace between the sand traps and the tutorial for the bugbait. The use of the antlions in the latter parts of this chapter keeps the pace changing because of how the antlions can be used, something discussed in the next chapter.

Chapter 9: Nova Prospekt

This chapter has a large amount of gates and because of the architecture of the chapter the player usually has a chance to see their objective but there is no direct path to it, this is another form of foreshadowing, and also used as a cue to convey information to the player about their objectives. 

There are turrets, tripod mounted automatic guns, positioned all around Nova Prospekt and they are used as a way to control the path the player takes. The mechanic for disabling the turrets (knocking them over) is shown to the player by the antlions which they can control.  Turrets are used in the next chapter by the player in a series of arena events, so showing the player now how the turrets are used, even if they are hostile, instructs the player on their effectiveness and mechanics.

Controlling the antlions presents an interesting pace choice to the player because they can choose to have their endless supply of antlions attack or they can go in guns blazing or both.  This choice is a lot like the decision to stay off the sand traps in the previous chapter, if the player chooses to let the antlions destroy everything, the pace of the sequences can be much lower than if they try to defeat all the enemies alone. This chapter has very few item crates in the antlion sequences, which is a way to limit the player because if they use the antlions exclusively, the player has plenty of ammo, but some puzzles require player action to proceed and the player can take damage that requires health items. 

Pace in this level is controlled by gates that require player action. There are also sporadic headcrab encounters and an antlion guard encounter which spike the pace. Overall this chapter’s pace is driven solely by the player’s choices in using the antlions and dealing with turrets.
Chapter 9a: Entanglement

This is the only subchapter of HL2. It is a subchapter because of its length and also because the setting does not change, Gordon is still inside the Nova Prospekt prison and he meets up with Alyx Vance. Alyx opens many of the gates (therefore they are story gates) in the beginning of this chapter allowing information to be told to the player via in-play cutscene and changing the pace from the antlion guard battle that ended the previous chapter. 

It is important for the narrative for Alyx to be able to manipulate Combine technology. It makes her seem smart and also allows her to control story gates. Therefore it makes sense that she can change the targeting of the turrets, making them attack the Combine. This turret mechanic switch is much like the bugbait and antlion mechanic. The player was shown the mechanics of these enemies while they were hostile so they do not need to be instructed on how to use them against the Combine. The friendly turrets are used in a series of arena battles throughout this chapter, which changes the pace from the in-play cutscenes that the player watches from Alyx.

Prisoner pods are also introduced in this chapter as Eli Vance is trapped inside one. The pods are coffin like containers that move prisoners on rails inside Combine structures. Pods become very important in Chapter 12 so showing the player early how the pods are used makes teaching them about their use easier later on. It is also another example of using foreshadowing to teach the player.

The investment the player has in the experience of HL2 is important in this chapter. The narrative has gotten exciting and now the pace may stay high for longer periods because the player will not get as fatigued as they would have earlier in the game. However, this subchapter’s pace does change between the turret arena battles and in-play cutscenes with Alyx making it follow the same pace formula as the other chapters in the lesser trials.

Chapter 10: Anticitizen One

This chapter in has longer and more frequent periods of high pace compared to previous chapters. After the narrow teleportation escape by Alyx and Gordon in the previous chapter, the resistance has begun their uprising. In order to smoothly integrate the now ruined City 17 and the advanced state of the uprising it was necessary to have the teleportation take a week to complete. More narrative tension is built up over this chapter because Dog gets swept away in battle, Eli is captured, Barney needs to be rescued, and Alyx gets captured. This is used to add weight to the player’s actions in the rest of the game and what they must accomplish.

Forcing the player back through the first set of streets they see in City 17 is a great design choice because it uses the feeling of nostalgia.  The player sees these ruined streets and the uprising happening and they remember the events that already happened in the game.

The hopper mine (hopper) is introduced in this chapter. Hopper mines are land mines that stick into the ground using spikes and when triggered they spring into the air and explode. As with many other mechanics the hopper mine is introduced to the player through use of an NPC and it then continues to follow the teaching cycle. The player can use the gravity gun to unearth hostile mines and plant them as friendly mines. The mines can also be thrown at enemies using the gravity gun much like other explosive items. By forcing the player to remove or otherwise dispose of hopper mines the pace of player is once again impacted and controlled indirectly so the player still has the feeling of control.

Throughout Anticitizen One, Gordon is joined by resistance citizens that assist him in dispatching the Overwatch, zombies, and headcrabs that are still in City 17. The citizens share some mechanics with the friendly antlions from chapter 9 (Gordon can control where they attack and move) but there are several key differences. First there is not an endless supply of citizens so once they die they are not replaced. Also some citizens are capable of healing other citizens and Gordon. This is important because some sequences have a noted absence of item crates and the need to protect the medic citizens becomes a priority. The choice the player had with the antlions again presents itself. How the player uses the citizens in battle impacts the pace of game experience.

The sequence in the warehouse is important because in several places the player gets to see a three-way interaction between combine, zombies and headcrabs, and barnacles. This adds to the chaotic environment that the narrative is supporting through the uprising.

Because Anticitizen One has resistance citizens that the player can control, and because the player is reaching the end of the game, the pace of this chapter is in higher than previous chapters and also switches less frequently.

Chapter 11: “Follow Freeman!”

Chapter 11, as a whole, could be considered a hard gate. The main objective of the chapter is to lower the suppression field so Gordon can get into the Combine Citadel. The overall pace of this level is high because the resistance uprising is reaching its peak and the player is quickly approaching the major trial of HL2.

Combine snipers have Barney pinned down in a ruined building in this chapter. There are also snipers at the end of Chapter 6. In that chapter the teaching cycle is used to show the player how to kill the snipers (throwing an explosive in their hide).  However, the headcrabs and crossing lines of fire makes the sniper sequence in this chapter the real challenge phase of the sniper skill teaching cycle. 

The Nexus building is protected by ground turret and ambushes of Overwatch troops.  Ground turrets act as platforming puzzles because if the player steps into their range they raise up and open fire. Learning to defeat the ground turrets is again done by a teaching cycle. The first ground turrets are directly in the player’s path and there is an endless supply of grenades that the player can use to destroy them. This acts as both the introduction and learning phase of the cycle. The next turret is encountered during a battle and is hidden around a corner, this is the testing phase. There is another turret inside the same room that the player cannot see form the door, because of this added difficulty and the probable lack of grenades at this point, this is the challenge phase. The turret skill is then reused throughout the Nexus building.

One of the main encounters inside the Nexus building is a platforming puzzle with ceiling turrets. This long puzzle breaks up the pace and also is used to give the player a stockpile of ammo and energy. This puzzle is even more important because the overall chapter pace of this and the previous chapter could fatigue the player if they are not given some prolonged break from the battles raging in City 17.

At the end of the previous chapter, the player is required to use the gravity gun to knock an energy orb out of a reactor to get a Combine gate open. There are three more energy orb reactors inside the Nexus building.  This energy orb mechanic is foreshadowing for the player to see that the Combine technology is usually beaten by the gravity gun (other examples are manhacks and rollermines).

In Point Insertion, the player saw a strider walk by a group of Overwatch. This chapter features the first battle with a strider. Striders are giant three-legged synthetic Combine units that can destroy buildings and must be destroyed by the RPG. The teaching cycle is slightly modified for learning to kill striders. The player is told by allies that rockets can bring them down and this serves as the introduction phase. However, there are also resistance citizens that launch rockets at the striders signifying the learning phase. Gordon using the RPG to take down the striders in the first battle is the testing phase. The challenge phase of this skill is one of the best in the game. After defeating several striders out front of the Nexus building Gordon is forced to take on a strider alone. Without a rocket crate that can give the player unlimited rounds Gordon is forced to go through a platforming puzzle with the strider attacking him. Once Gordon finds the rocket crate, he can then destroy the strider, making the strider killing skill concrete for the player.

The energy orb puzzles in this chapter are used to control the players pace and keep them inside the Nexus building so that when the large courtyard battles with striders occur the player gets the full sense of scale. The need to find rocket crates to dispatch striders is also used to control the player’s pace. This is the last chapter of the minor trials so the player is treated to a lot of RPG targets (striders) and large arena battles as a reward for making it this far.

Chapter 12: “Our Benefactors”

“Our Benefactors” is the first chapter of the major trial in HL2. Gordon must infiltrate the Combine Citadel to save Eli and Alyx Vance. The Citadel is a massive structure that the Combine uses as their base of operations on Earth and where the Administrator of Earth, Wallace Breen, has his administration and office. The Citadel holds prisoners, contains teleportation equipment, and is used to build synthetic Combine entities like gunships and striders.

The cliff walk at the beginning of this chapter is a perfect example of a vista. By forcing the player to do platforming puzzle elements on the cliff face they look up and down the entire Citadel getting a sense of its gigantic scale and how alien the structure is. It also gives the player a low paced sequence before the high-paced action inside the Citadel. The pods inside the structure are basically moving vistas. The player enters them and is treated to rich visuals that show the inner workings of the Combine and the Citadel. They are also used to control pace because the player can only move the camera when in a pod so it gives the player a chance to relax in-between battles. The pods also pose an interesting question to the player: “Where will Gordon get off?”

Once Gordon is caught after his first pod ride, he gets his weapons removed and destroyed save for the gravity gun which has been modified by the Citadel’s automated defenses. Now the gravity gun has longer range and can be used to grab and throw organic matter including Overwatch troops.  Another interesting side-effect of the gravity gun’s modification is that now the weapons of the dead Overwatch troops are destroyed. This forces the player to use only the modified gravity gun throughout the level. This change also makes combat with normal troops mostly trivial, they can be tossed around and killed very easily. This is important for two reasons: it allows for fights against vast numbers of Overwatch and also it makes the major trial different but not too difficult. Because the Citadel is a Combine stronghold the large number of Overwatch troops makes sense in the narrative and gives the player a sense of how powerful they and the gravity gun have become. It also completely changes the combat without making it too hard, which a fatal flaw of many games is making the last levels so difficult that players simply give up.

To match the new power Gordon wields with the modified gravity gun there is also a new kind of suit recharger inside the Citadel. This new recharger can quickly refill Gordon’s suit energy to a higher level and can refill his health. This is another example of making the gameplay for the major trial different instead of difficult.

Wallace Breen appears on screens throughout the Citadel and often talks about Black Mesa and the fact that Gordon is a physicist; this again is a play to the emotion of nostalgia.  It also reminds the player of the scope of HL2 and how all of this started in the original Half-Life. This is a strong narrative tool that is amplified by the fact that Gordon never replies to him. Gordon has not spoken in any of the Half-Life games, a design choice that fits in with the philosophy of complete player control because the player cannot choose what Gordon says, he says nothing.

Another mechanic of the modified gravity gun is that it can be used to grasp and fire energy orbs.   The player has seen the orbs as the secondary fire type of the combine rifle (an automatic weapon carried by the Overwatch also called the AR2) and in the Nexus building power cores in the previous chapter.  This is yet another example of the use of foreshadowing and modification of previous mechanics to teach the player new and interesting mechanics.

There is a boss fight in this chapter that is a strider battle that highly resembles the final encounter with Breen.  It is used as the challenge phase of the energy orb teaching cycle and also allows the player to practice grasping orbs from the energy beams on either side of the arena and use them to destroy a large enemy.

The player’s pace in this chapter is broken up between visually stimulating pod rides and fast-paced modified gravity gun battles. The players investment is peaking in this chapter, because it is the major trial, so the changes in pace a somewhat less important because the player can endure longer periods of high pace. The more important mechanics for pace in this chapter have to do with making the gameplay different instead of difficult because at this point the player just wants to reach the end of the game.

Chapter 13: Dark Energy

Dark Energy is the final chapter of HL2. This chapter opens with Gordon still trapped in a pod and unable to move but the player still retains control of the camera.  The Overwatch has captured him and taken his modified gravity gun.  The following in-play cutscene is the narrative climax of the game.  Once the cutscene is complete Gordon is released from the pod and is back to where he started the game, defenseless. 

Gordon soon receives the modified gravity gun again and is told by Alyx that his objective is to stop Wallace Breen.   What follows is a very fast paced sequence including platforming, energy orbs, and combat.  It is the culmination of all the puzzle mechanics in HL2 and the fast pace and intensity are a change from the in-play cutscene where Gordon was trapped in the pod. 

Once Gordon reaches the top of the platform, the player has completed the final puzzle of HL2. Now Gordon begins the final encounter that closely mirrors the strider battle in the previous chapter. Because the player just had an encounter like this one at the end of the previous chapter, the orb and gravity gun mechanics are fresh in their mind and they need no teaching. The challenge comes from dealing with two gunships and destroying the Citadel reactor before Breen escapes.
 
After Dr. Breen is destroyed there is a short in-game cutscene with Alyx, and then the closest thing to an actual cutscene since the opening sequence.  It is another conversation with the G-man.  How the G-man saves Gordon is a textbook form of deus ex machina, which reinforces the loss of control that the G-man represents. Deus ex machina literally means “god from the machine” and in a narrative it is used to describe a sudden unexpected ending to an impossible problem. Gordon and Alyx are caught on top of the reactor during an explosion that will most certainly kill them. Gordon is seemingly plucked from space and time by the powers of the G-man and saved. The pace in this short narrative chapter changes from low during the pod in-play cutscene to high during the final puzzle and Breen encounter and then back to low during the G-man cutscene. This ends HL2.
Conclusion and Personal Experience

I have played completely through HL2 three times and I could play it ten more times without getting bored. However, there are two aspects of the game that I left out of this analysis because they are not really innovative or interesting: the story and conventional weapon combat.

In hopes of not completely ruining the game for any readers that have not played HL2, I intentionally left story out as much as possible, but I also left it out because the story of HL2 is nothing special. The characters are well designed, believable, and memorable but the story doesn’t really have any surprises.  The most innovative part of the story is the in-play cutscenes and how they deliver the narrative to the player. The weak story is also hurt by the player control design decisions. The lack of objectives and formal cinematics makes expressing a compelling narrative very difficult because while story gates are used the player ultimately has control over what they see and hear.

Conventional weapon combat was also not discussed because while it is well-executed, it is not very innovative.  The game has some great weapons (I especially like the Combine AR2 and the Magnum Pistol) and the enemies’ behaviors and reactions are very believable due to their unscripted nature, but this is what every great FPS needs to have. However, the grenade mechanic of HL2 feels dated and several of the other classic weapons from the original Half-Life are just boring (pistol, shotgun, and AR1). Many FPSs that were released in the same time frame as HL2 (such as Halo 2f) moved away from allowing the player to carry over 10 weapons because it is very difficult to make the mechanics of that many weapons meaningful. In HL2, the tight ammo constraints of the crossbow and RPG try to make up for the large arsenal, but all it does is limit the player’s use of some of the most fun and unique weapons. 

HL2 is one of my favorite games of all time.  It may not be the most fun, have the best graphics or story, but the design of HL2 is flawless.  How the player’s pace and flow is controlled and how they are taught mechanics through a teaching cycle gives a rich experience that is unmatched. The blending of narrative, combat, and vehicle chapters keeps the player on their toes and prevents fatigue and boredom while enhancing the feeling of flow. By teaching the player a wide range of related mechanics (such as fighting the antlions, then later controlling them) throughout the game the player is constantly shown something new that also feels natural and intuitive. If HL2 did not have a first person camera, it would never be considered a first person shooter because the more innovative and fun aspects of the game have little to do with shooting. The most memorable levels, Chapter 6 and Chapter 12, push the limits of what a FPS can do with combat, pace, flow, and intensity. The haunted house of HL2 is chocked full of friend and foe, combat and puzzles, and intensity and loneliness, but it offers a unique experience of player control that has never been matched.

________________

a) Half-Life 2, Valve Corporation, Vivendi Universal Games, Nov. 2004
b) Half-Life, Valve Corporation, Sierra Studios, Nov. 1998
c) Orange Box, Valve Corporation, Valve Corporation, Oct. 2007
d) Half-Life 2 Episode: 1, Valve Corporation, Valve Corporation, June 2006
1) Developer Commentary: Chapter 1: Undue Alarm, part 2, 1/10, Charlie Brown
2) Developer Commentary: Chapter 4: Urban Flight, part 4, 1/10, Gautam Babbar
e) Half-Life 2 Episode: 2, Valve Corporation, Valve Corporation, Oct. 2007
1) Developer Commentary: Chapter 1: To the White Forest, part 2, 2/2, Ted Backman
2) Developer Commentary: Chapter 6: Our Mutual Friend, part 2, 8/11, Kelly Bailey
f) Halo Series: Halo: Combat Evolved, Bungie Studios, Microsoft Game Studios, Nov. 2001; Halo 2, Bungie Studios, Microsoft Game Studios, Nov. 2004; Halo 3, Bungie Studios, Microsoft Game Studios, Sept. 2007
g) Gears of War Series: Gears of War, Epic Games, Microsoft Game Studios, Nov. 2006; Gears of War 2, Epic Games, Microsoft Game Studios, Nov. 2008
h) Half-Life 2: Lost Coast, Valve Corporation, Valve Corporation, Oct. 2005
1) Developer Commentary: 8/14, Robin Walker
2) Developer Commentary: 13/14, Robin Walker
i) BioShock, 2K Boston/2K Australia, 2K Games, Aug. 2007
j) Doom 3, id Software, Activision, Aug. 2004

1. Awards and Honors of Half-Life 2, http://www.valvesoftware.com/awards.html, Accessed in Nov. 2008
2. Metacritic, http://www.metacritic.com/games/platforms/pc/halflife2, Accessed in Nov. 2008
3. Shoot to Thrill: Bio-Sensory Reactions to 3D Shooting Games. Tim Hong. Game Developer Magazine, Volume 15, Number 9, Oct. 2008
4. Game Design Workshop: Designing, Prototyping, and Playtesting Games, page 307. Tracy Fullerton, Christopher Twain, Steven Hoffman. CMP Books, 2004
5. The Orange Box Original Soundtrack, track 1. Valve Corporation, 2008
6. The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information. George A. Miller. The Psychological Review, pages 81-97, Volume 63, 1956
7. Introduction to Human Factors Engineering, Second Edition, pages 128-134. Christopher D. Wickens, John D. Lee, Yili Liu, Sallie Gordon-Becker. Prentice Hall, Nov. 2003
8. The Cabal: Valve’s Design Process for Creating Half-Life, The Game Design Reader, pages 212-225. Ken Birdwell, Katie Salen (editor), Eric Zimmerman (editor). The MIT Press, 2006
9. The Art of Game Design, pages 252-253. Jesse Schell. Morgan Kaufmann Publishers, 2008
10. A Walk Through Portal: An Act of Videogame Analysis, Games + Learning + Society 4.0 Conference. Drew Davidson. July 2008
11. Flow: The Psychology of Optimal Experience. Mihály Csíkszentmihályi. Harper Perennial Modern Classics, July 2008.
12. The Art of Game Design, page 122. Jesse Schell. Morgan Kaufmann Publishers, 2008