Independence War 2: Edge of Chaos (American title), or Edge of Chaos: Independence War 2 (European title), is a sequel to the space combat simulator video game Independence War (also known as I-War in Europe). Developed by Particle Systems Ltd - the developers of the first game - and published by Infogrames, the game was released in 2001. It was nominated for an interactive BAFTA award for its soundtrack  which was composed by Christopher Mann.
Edge of Chaos is set in the 24th century, 100 years after the first game, in an isolated part of space called the Badlands Cluster. The Star cluster is far removed from Earth, the Core Systems, and their central governing body, the New Alliance; also, the Alliance government was in a state of near-collapse due to corruption and massive overspending. As a result, huge corporations step in to take control, and they rule quite tyrannically.
The game begins with a CGI video showing the murder of 12-year-old Cal Johnston's father by industrial heir Caleb Maas. The player then assumes the role of young Cal as he is instructed in space ship piloting by the digitized personality of Commonwealth Navy captain Jefferson Clay, a character familiar from the original I-War. After getting used to basics of space flight, Clay guides Cal to the base of his space pirating grandmother. After some more practice missions, Cal encounters the infamous Caleb Maas. Trying to avenge his father, Cal ends up in prison instead. The story then fast-forwards 15 years showing a now-adult Cal Johnston with some of his fellow inmates escaping the prison space station, where the core gameplay begins.
Upon returning to his grandmother's base, Cal begins to set up his own piracy organization. Other groups in Hoffer's Wake begin to notice his work, and as he advances in fame and fortune he learns more about the current situation affecting the Badlands. For a long time, a group called the Marauders have been attacking at random—essentially terrorizing the people of the Cluster. Despite numerous attempts to run them down, the Badlands government and gangs have had no luck in stopping the attacks: the Marauders don't seem weakened even by major losses, and they don't seem to have any single base of operations.
The player is soon given access to other systems in the Cluster, with the assignment to find help fighting the Marauders in Hoffer's Wake. Most are only too happy to lend ships, supplies, and personnel once their own Marauder problems are taken care of, and the Marauders are successfully driven from Hoffer's Wake before long. However even that loss didn't slow them down, and further investigation on Cal's part reveals that they have been maintaining their primary base in the Dante system, long abandoned and thought uninhabitable after the unstable binary star flooded the system with radiation and cut it off from outside travel. The Rebel Fleet, now very large and well-organized, mounts a successful assault—only to be nearly destroyed anyway when the Marauders receive help from the Maas Corporation, who started the Marauders to "keep you peasants in line."
The Rebels can't hope to directly match Maas's forces, so they fall back and try to think of alternative strategies. They conclude that the most effective action would be to find help outside of the Badlands, so they attack and secure the Santa Romera Jump Accelerator, a highly advanced piece of technology that allows travel over significantly longer distances than even Lagrange points. Cal arrives in the Fomalhaut system in the Gagarin Cluster to find much the same situation as in the Badlands: oppressive corporate rule, roving Marauders, and a desperate need for assistance.
After working for a while, Cal receives a seemingly innocuous mission in which he is sent to spy on a number of corporate cruisers in the Gagarin Cluster. The story takes a sharp turn when, against Caleb Maas's wishes, corporate scientists activate an alien artifact that Cal himself stole for them, thinking to use it as some sort of weapon. The device goes out of control and begins to emit glowing red alien ships that eat (and thus destroy) any advanced power sources (such as ships) in their path; within days, the entire Gagarin Cluster is overrun. Cal and the fleet hold the aliens back from the Fomalhaut Jump Accelerator as refugees escape, then dash through at the last second and destroy the Accelerator, effectively isolating the Badlands indefinitely from the rest of human civilization. Cal remarks that they are safe from the aliens, but he's not sure about human civilization elsewhere.
The gameplay is a mix of free movement in space and missions. In free play, Cal can act independently, move throughout the Hoffer's Wake system and eventually the entire Badlands Cluster, and steal cargo. Game missions allow the player to gain new weapons and ships, and contribute to the rebellions against the corporations that control the Badlands.
The game may only be saved when a player returns to their 'base'. While docked here, in addition to saving, the player can also elect to change their current ship type or equipment loadout; check their inventory of current equipment and cargo; trade stolen cargo for new equipment on the black market; and manufacture various types of munitions from recycled scrap. A final and highly important function of the base is to allow access to the player's email file, which is the main process to learn about new missions and plot developments.
When the game first starts, the player as the younger Cal is flying a Command Section or ComSec, a detachable mini-ship that is intended to be part of a larger vehicle and has minimal capabilities of its own. After the player docks at their base for the first time, they will gain access to the Storm Petrel, a lightly armed but very fast fighter craft which is easy to fly for new pilots. After crossing Caleb Maas and being sent to prison, the Petrel is lost, and the player now flies a Spider-class tug. Later in the campaign, the player will also be given access to the Tachyon-class patrol-combatant (PatCom) and the Devastator-class heavy corvette. These craft only become available after key, difficult missions and are much more powerful and capable than the tug ship.
There are a wide variety of upgrades available to the player. Some few are given in the form of stolen cargo pods or through mission rewards: most are gained on the black market through the base's trading interface. Upgrades can either add new features to the ship (like installing the Imaging Module, which lets the player zoom in their view dramatically), others simply improve the ship's performance (such as installed cold gas thrusters, which are not quite as powerful as standard thrusters but much more stealthy in use). Once gained, upgrades are permanently available to the player, though may be moved between ships as desired.
Weaponry in Edge of Chaos is modular. Each ship has some number of hardpoints available, and the player is left with the option of how to arm the ship from the available weapons in their inventory. Weapons are divided into three categories:
- Primary weapons are various shell- and energy-based cannons which carry unlimited ammunition or great quantities of ammunition. Primary weapons are typically ineffective at long range. The player's primary weapons will automatically track the selected target within a small cone of the ship's forward facing: that is, the player does not need to manually line up their gun sights. Primary shots do not seek the target once they have left the weapon however. Some examples of primary weapons include:
- Rapid-fire particle beam cannon (PBC). A slightly inaccurate but fast-firing energy weapon that can deliver an effective short-range burst.
- Wide-arc PBC. This cannon can track your current target to a greater degree than others, meaning that you don't need to turn as far toward the target in order to open fire on them.
- Gatling cannon. An extremely fast-firing weapon that delivers high damage, but the player must take care not to run out of ammunition, which can only be reloaded back at the base.
- Sniper cannon. A long-range heavy weapon, fitted with a scope to help the user take down ships from great distances.
- Cutting beam. An extremely powerful short range weapon which is difficult to use against small evasive targets, but can destroy larger ships with ease.
- Secondary weapons are fitted into a ship's missile launchers, should the player elect to mount any. Secondary weapons typically offer a great deal of power at the expense of very limited ammunition. Secondaries offer a lot of flexibility and come in many families each of which has at least one actual type of ordnance:
- Dogfighting missiles will aggressively seek the target you had when you launched the missile until they run out of fuel. These missiles can make multiple attempts at a single target, fly for long distances, and will continue to pursue even if you select another target.
- Rockets do not seek a target, so are very difficult to aim in Edge of Chaos with its Newtonian physics. However you can fit far more rockets into a launcher than you can missiles, and rockets possess similar power and range. They are best for attacking very slow or stationary targets from long range.
- Disruptors are guided missiles which do not cause any damage, rather, they disable the target briefly. This can take them out of the fight long enough for you to escape, or simply leave them open to other attacks.
- Remote missiles are flown manually by the player after they are launched from the ship. The player also chooses when to detonate the missile. While they are large and difficult to use, they are exceptionally powerful and have a large blast radius.
- Mines can be used to set up ambush points, with both proximity-detonated and self-guided mobile versions.
- Special weapons are devices which offer some sort of attack capability but aren't cannons or launched ordnance:
- Turret fighters can be added to the player's ship once they find these fighters. While docked to the ship, they function as port and starboard gun turrets to whom a target may be assigned to fire on. They can also be ordered to fire automatically at any hostiles within range. Optionally, the turret fighters may be undocked from the ship, in which case they become the player's wingmen and completely independent fighter craft. While more vulnerable in this state, they are also much more agile.
- A Docking auto turret is a robotic light gun turret which can be added to the bottom of the player's ship, and automatically attacks enemies within its view.
- An Anti-missile turret automatically shoots at missiles that are seeking the player's ship.
- The Aggressor Shield allows vicious ramming attacks to be made, where the player will take far less damage than the target they have rammed. Timing is crucial, since the Aggressor Shield is only active for a few seconds.
The Heads-Up Display in the game includes several features iconic to the Independence War franchise, including:
- Spherical radar, which indicates the positions of other vessels and waypoints as points on stalks that extend in or out of the surface of a sphere (depending on distance), offering a simple three-dimensional view of the situation
- HUD lines, which create a sensation of motion by sliding past the viewer as the ship moves; they are also color-coded to indicate rocket versus LDS movement
- Targeting ladder, which shows the path of other ships as a color-coded ladder, each step representing the ships position after a certain fixed interval; this allows the player to track the past movements of other ships and use this information to predict their future movements
Because it is a partially freeform game modeling an entire star cluster at plausible scales, players of Edge of Chaos will often find it necessary to transit considerable distances. There are three forms of travel in EoC:
- Real space or normal space, where the laws of physics apply. The player controls their rotation and movement by the use of thrusters and the main drive. This is the mode where all combat takes place. While the player is not limited in terms of their maximum velocity and could simply turn in the direction of their destination and continue to accelerate, it would take literal weeks or months to cross the game's interplanetary distances, which may exceed one billion kilometres.
- Linear displacement systems (LDS) allows rapid travel. In LDS, weapons cannot be fired (with the sole exception of weapons designed to knock other ships out of LDS), and craft are not subject to the laws of physics. While in LDS, the player steers their craft normally as they pass through space: planets and stars visibly move. The game's fiction suggests that LDS is meant to be only as fast as light, though in the actual game the speeds are much higher[; this was probably done to make long distance travel less time-intensive. ]
- Capsule space. Partway through the campaign, the player gains access to a capsule drive, an upgrade for their ship which allows instant travel across huge distances. Capsule space jumps can only be charted between Lagrange points, abbreviated in the game as 'L-points'. Capsule jumping is also the only way to travel between the game's star systems.
The game's autopilot system can be used most of the time to eliminate the tedium of travel. However it is completely possible (and in some situations, necessary) to choose one's own capsule jump destination or to manually operate the LDS drive.
The game adheres well to the laws of Newtonian physics, realistically approximating the actual behavior of spacecraft; ships have inertia and take time to change speed and direction. The player's vessel is equipped with lateral thrusters that allow it to move without changing its direction of facing.
This has immediate effects on the game; for example, combat is often won based on how well the respective pilots can use their ship's inertia to best advantage, rather than who has the best weaponry.
The physical simulation applies to even weapon shots and missiles, which inherit their initial speed from the ship that created them: flying left and firing will create a bolt that goes straight from the firer's perspective, but to outside observers would seem to travel partially sideways. This behaviour makes it challenging to use weapons without the automatic computer-assisted weapon tracking behaviour.
The technological improvements over the first game included support for Direct3D compatible hardware accelerated 3D graphics, network multiplay and a new user interface. Edge of Chaos gave a nod to Elite style gameplay by adding free roaming piracy to the Independence War games' universe. The familiar Newtonian mechanics obeying flight model with a flight computer assistance was retained, although combat was somewhat simplified and made more accessible to the player.
Edge of Chaos was initially developed for both Windows based PCs, PlayStation, Nintendo 64 & Dreamcast, but the PlayStation, Nintendo 64 & Dreamcast version was cancelled. The dual platform development affected some design decisions. Most of the ship's function interface was made navigable through a joystick hat control, but on the negative side, partly due to being designed for a game console without a hard disk, game progress could only be saved between missions, in the home base.
The game was a critical, but not financial, success, contributing to the eventual acquisition of developers Particle Systems by Argonaut Games, which changed the team name to Argonaut Sheffield. Edge of Chaos was distributed by Infogrames Entertainment.