Game Boy Advance

Both Doom and Doom II have been released for the handheld console Game Boy Advance.

Doom


In 2001, a Game Boy Advance version of Doom was released by David A. Palmer Productions. It has several differences from the original game:


 * Simplified levels based on those of Jaguar Doom.
 * Neither cyberdemons nor spiderdemons are present, but the final level has several cacodemons.
 * Spectres are either removed or replaced with demons.
 * Cacodemons move much faster than normal.
 * The only secret level remaining is E1M9. The game does not prompt the player to save upon entering this map, so it must be completed in the same session it is entered.
 * Part of E2M2 has been removed, although a few rooms remain, though they are inaccessible. Because of this, you cannot obtain 100% secrets on this level.
 * Part of E2M5 was taken out.
 * E2M7 is quite different.
 * E2M8 is completely different.
 * E3M1 is completely different.
 * E3M2 has been removed.
 * Some of E3M6 has been removed.
 * No E3M9; E2M8 is the original E3M8.
 * All music is "shifted ahead" (E1M1 uses E1M2's music, E1M2 uses E1M3's music, and so forth, until E3M3 is reached).
 * The box of bullets is a brighter shade of green.
 * The BFG9000 can be found in secret areas of Episode 2, The Shores of Hell.
 * No crushing ceilings.
 * The blur artifact and light amplification visors are removed.
 * Health potions and spiritual armor give 2% instead of 1%.
 * The monsters' blood is green, as is the blood produced when the player takes damage. Doomguy's face in the HUD does not bleed when health values are low (though it does take on a progressively disheveled appearance).
 * Sound propogation appears to be unused, probably in order to conserve performance; all enemies are deaf as a result.
 * Monster corpses vanish after a few seconds.
 * Much Hell-related and gory imagery is missing (impaled bodies, etc.).
 * Ultra-Violence mode is renamed "Nightmare"; true Nightmare mode was removed altogether.
 * The game can only be saved between levels.
 * No animated or text intermissions appear for the first two episodes' completion.
 * When a message indicating a collected item, etc. is displayed on-screen, receiving a new message (e.g. collecting another item) does not reset the amount of time the message is displayed; the new message will disappear at the same time the first message was supposed to disappear.
 * In vanilla Doom, the Tower of Babel appears to be "built" during episode 2: with each intermission screen, the tower becomes a little larger, growing from a foundation to a full tower. This does not happen in GBA Doom.
 * Altered ending text: episode 4's ending screen appears instead of the famous "bunny" ending (probably to avoid an M rating).
 * Demon death sound is replaced with imp death sound.
 * A bug makes palette index 0 transparent.
 * The status bar has no "%" sign and uses a different font for its numbers.
 * "Static lighting" option added, which makes the light amplification visors useless (hence their removal from the game). This was possibly done for performance reasons, as the frame rate increases when the light calculation code is skipped; however, it also makes the game easier to play under less than ideal lighting conditions (as the original series of Game Boy Advance did not have a backlit or sidelit screen, making dark areas difficult to discern under poor lighting conditions).
 * Although framerate usually does not fluctuate, the actual game speed can differ depending on the amount of processing happening at any given time; usually, this results in slowdown from heavy processing, but occasionally, during areas of relatively light processing, the game can actually run faster than normal (especially with the "static lighting" option enabled). Slowdown is especially common during multiplayer modes, particularly cooperative.
 * Lighting affects level geometry, but not Things; all enemies, items, and decorations "glow" in the dark (instead of just specific Things like Lost Souls or light source objects like lamps).
 * Changes to the lighting engine also resulted in lessened depth perception. In original Doom, and most console ports, surfaces nearer the player are drawn brighter than surfaces farther from the player, even if both surfaces are in a sector with the same lighting level. Likewise, surfaces running north-south are shaded slightly differently than surfaces running east-west, even if all such surfaces are in a sector with the same lighting level. Both of these features assist in depth perception by creating contrast between surfaces, but are not present in the GBA version of Doom, perhaps due to the added processing and dithering needed to render them.
 * When you collect a invincibility power-up, rather than the colors going black and white, the screen has a deep blue haze.
 * There is a bug related to item collection, where if two or more items are located in close proximity (roughly 32 units or so), neither item will be collected if the player walks over them, unless the player can pick up all such items. For instance, if a Clip and a Stimpack are directly adjacent, and if the player has 100% health, he will not be able to collect the Clip, regardless of his bullet amount, since he is not allowed to collect the Stimpack.  This bug was also present in the PlayStation version of Doom, and possibly earlier versions.

Multiplayer
The GBA version of Doom also came with eight brand new deathmatch levels. These are the only officially released multiplayer-only levels for the classic Doom games, and are (along with American McGee's ) the only official multiplayer levels ever released; the levels have not been released commercially on any other system. The author is presently unknown.

Playing Doom multiplayer on GBA systems is only possible by connecting the GBA systems using a separate Game Link Cable, GBA Wireless Adapter or other similar accessory for connecting the devices.

Weapons that appear in GBA version

 * Fists
 * Chainsaw
 * Pistol
 * Shotgun
 * Chaingun
 * Rocket launcher
 * Plasma rifle
 * BFG9000

Enemies that appear in GBA version

 * Zombieman
 * Shotgun guy
 * Imp
 * Demon
 * Lost soul
 * Cacodemon
 * Baron of hell

Doom II


Torus Games of Australia developed Doom II for the GBA, which was published by Activision. Note that this game is not a port of the original Doom engine, but instead runs a custom engine shared with several other GBA first-person shooter games called the Southpaw Engine. The differences between the GBA Doom I and Doom II (besides the maps):


 * All maps and monsters are present (including the Wolfenstein secret maps and Wolfenstein SS enemy).
 * The demon was given its original death sound.
 * The original status bar numbers are used.

Since the original Doom engine was not used, all content and mechanics had to be converted over to the Southpaw Engine. Converting the original Doom II content to the Southpaw Engine resulted in a number of visual and mechanical inconsistencies from the original game; some are mostly cosmetic, but some can have a significant effect on game functionality. Additional differences from the original Doom II not already mentioned include:
 * The super shotgun's shells are flesh coloured, just like the face's blood.
 * The super shotgun reloads faster; also, its sound effects are not synched to the animation, resulting in the animation playing longer than the sound effects.
 * The shotgun's behavior was changed so that it fires in a conical pattern instead of a fan pattern; though this behavior is more "realistic", it deviates from the original design of the weapon and affects its usage significantly, as "grazing" indirect hits or hits against multiple enemies are much more difficult due to the substantially lessened horizontal dispersal.
 * The chaingun no longer fires in bursts of 2; instead, it fires only 1 bullet at a time when used.
 * The Pistol and Chaingun no longer fire with perfect accuracy when single shots are fired; instead, the bullets are fired with the same deviation as though fired during a sustained burst. This makes "sniping" or chaingun tapping nearly impossible.
 * The Chainsaw pushes enemies away from the player, instead of simply dragging the player into the enemy; this makes using the Chainsaw risky and difficult, as the enemy can be pushed out of the Chainsaw's area of effect, allowing the enemy a chance to counterattack.
 * The Plasma gun no longer plays the "recoil" animation that normally plays after releasing the attack button; this makes consecutive usage of the weapon (such as single shots or short bursts) faster.
 * Dropped weapons and items give full ammo, instead of half.
 * The box of rockets gives ten rockets, not five.
 * A message is displayed on-screen when the player finds a secret area.
 * Doomguy's status bar face changes at different health values than in the original game (about 5 - 10 points lower health for each transition).
 * The music tracks "Between Levels" (MAP04) and "Getting too tense" (MAP28) were dropped, most likely due to cart space. In their place was "Into Sandy's City" and "Evil Incarnate", the music to MAP09 and MAP31, respectively.
 * "I'm Too Young To Die" does not give double ammunition; it only reduces damage.
 * Like the original GBA Doom, "Ultra-Violence" was renamed to "Nightmare!"; true "Nightmare!" was removed.
 * The color palette used is not identical to the color palette used in the original Doom games, resulting in some objects or surfaces suffering from palettization issues, especially under certain lighting/colormap conditions (such as being under the influence of a Berserk Pack). Browns and tans seem most affected. The Pain Elemental displays this more noticeably than other examples; its body appears slightly splotchy even under "normal" lighting. The first "episode" skymap also illustrates this.
 * Monster blood is green instead of red, and most instances of extreme gore (such as gibbing) were removed. Additionally, if the player is damaged, a bullet puff is produced instead of a blood splatter. (This edition is rated "T" for Teen, whereas most editions received an "M" for Mature.)
 * Enemies are drawn slightly larger relative to the environment than in other versions of the game; however, their bounding boxes are not scaled to the same degree. This makes shots tend to "miss" when they should appear to hit, if the shot was aimed at the periphery of a monster's visual representation.
 * Vertical auto-aim is not reliable; the game will usually not aim for barrels on a lower atltitude than the player, and Hitscan shots fired at floating/flying enemies at close range will sometimes be fired above or through the monster instead of at the monster.
 * The player is now allowed to walk underneath flying enemies, or jump over the heads of monsters below. (This was possible in Doom engine games like Heretic and Hexen, but was not allowed in Vanilla Doom.)
 * Monster corpses will obstruct the motion of a door, causing it to reverse its motion if it tries to close on a corpse (as opposed to crushing or destroying the corpse). Since monster corpses disappear after a few seconds, this is only a temporary issue.
 * Enemy AI will shut off at times to avoid slowdown due to heavy processing. The decision by the engine to shut off any given enemy's AI seems to be based upon a combination of distance and/or number of sectors between the monster and the player, and NOT based exclusively (if at all) on whether or not the player is within line of sight. Such a monster can sometimes even be shot and damaged by the player and remain "dormant" (an example is the Imps across the water in the first outdoor area in Map 03: Gantlet).
 * Player movement when strafing or backpedaling is much slower relative to other versions of Doom, making it much more difficult to avoid Projectile attacks or sudden ambushes (which are extremely common in this game).
 * The bounding box of the Lost Soul's attack is much larger than it should be, and causes the player to receive damage if the player is within several feet of the Lost Soul in any direction when it attacks (sometimes even if the player is behind cover or around a corner) and not just on a direct hit. Not only does this result in many "cheap" hits against the player, but it also makes using the Chainsaw impractical, as the player will suffer damage from the Lost Soul's attack long before the Chainsaw can make contact with the Lost Soul.
 * Revenant missiles do not smoke when homing, and are fired from the revenant's waist (~32 units high, like all other missiles). Non-homing missiles are rarely (if ever) fired.
 * The arch-vile's flaming sounds are missing and the explosion sound (DSBAREXP) is played when the attack is initiated. Also, the flames appear lower in the player's view, and damage dealt is dramatically lower.
 * The Mancubus turns his body roughly 45 degrees from the player during his first and second attacks (instead of simply aiming his attack slightly off-center), which usually causes his projectiles to miss badly. His third attack is performed roughly as usual.
 * The BFG's tracer attack uses the BFG plasma balls explosion sprites and the explosion sound used for the BFG plasma balls impact is the standard explosion sound rather than its own.
 * Health items (such as Medikits and Stimpacks) are now erroneously counted towards the "Items" tally at the end of the map, making a score of 100% difficult to achieve (since health items can only be obtained if the player is not at full health).
 * Enemies killed by traps or friendly fire from monster infighting are erroneously not counted towards the "Kills" tally at the end of the map.
 * Industrial Zone and The Chasm are split into two maps each to avoid slowdowns and memory constraints. However, the scoring on these maps was not adjusted to reflect the removal of the enemies, secrets, or items relocated to the corresponding "second" map, making a score of 100%/100%/100% on these levels impossible. (Whether the "removed" entities are still present in the map, or whether these maps have a special hard-coded scoring exception, is unclear.)
 * The Wolfenstein secret maps and Wolfenstein SS enemy are present, but all Nazi imagery and Hitler paintings have been replaced by iconography from Return to Castle Wolfenstein (presumably to maintain the game's "T" Rating by the ESRB).
 * Weapon damage dealt to other players during Deathmatch is reduced by 75%, making Deathmatches much more protracted than usual.
 * The Armors calculation system in this game is somewhat broken; if the player enters a map with any armor percentage above 0%, the game will ignore the player's armor value until an item which affects armor value is picked up (either Armor, Megaarmor, a Megasphere, or an Armor bonus will work); this will "restart" the armor system to work correctly, and any armor collected during the map will function as expected. If such an item is unavailable, then the player is, for all intents and purposes, forced to play with no armor, even if the player's actual armor value indicates the player should be protected.