Game Boy Advance

Both Doom and Doom II have been released for the handheld console Game Boy Advance. Both games were produced by different studios using different engines, and vary in terms of fidelity to the original products.

Doom


In 2001, a Game Boy Advance version of Doom was released by David A. Palmer Productions. It uses a version of the engine created for the first series of console ports during the 1990s, so its gameplay is generally very true to the original, albeit with less overall content. It does, however, have several differences from the original PC version of the game; some of these are unique to this version of the game, while other differences are common to the other early console ports it shares its code base with:


 * It uses the exact same map set as Jaguar Doom, with the same simplified geometry, reductions in textures used, and areas removed, as well as some of the same bugs. For details on the changes made to each level, see Atari Jaguar.
 * Although the game features an episode select screen, the game itself is not actually divided up into episodes (and has no episode transition screens). All maps can be played back-to-back, with inventory from one episode carrying over to the next. Thus, the episode selection screen serves more of a "level skip" function, allowing the player to start from later maps.
 * As in the Jaguar version, neither cyberdemons nor spiderdemons are present, and spectres are either removed or replaced with demons.
 * Cacodemons move much faster than normal.
 * Game progress can only be saved between levels. There are four save slots available to use. The player cannot save upon entering E1M9, so it must be completed in the same session it is entered.
 * 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). Also, its color depth is noticeably lower than in other versions of the game, resulting in less detail.
 * Sound propogation appears to be unused, probably in order to conserve performance; all enemies are deaf as a result. (Some monsters periodically become active before they enter line-of-sight, but whether this is due to sound propogation--or some other cause, such as a reject map bug--is uncertain.)
 * 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 ending is modified; episode 4's ending screen appears instead of the famous "bunny" ending.
 * The screen only displays one message at a time; new messages immediately supplant old messages.
 * The Tower of Babel does not change appearance from one intermission screen to the next.
 * Demon death sound is replaced with imp death sound.
 * When the player drops off a high ledge, he makes the pain sound instead of the usual "oof" sound.
 * Punching a wall (usually including a 2-sided line, such as the front of a door) generally produces the same impact sound effect as punching a monster.
 * A bug makes palette index 0 transparent.
 * The status bar has no "%" sign and uses a different font for its numbers.
 * A "static lighting" option was added, which renders all sectors at full brightness. The frame rate increases when this is enabled, and it also makes the game easier to play, since the original Game Boy Advance model does not have a backlit or sidelit screen, making dark areas difficult to discern under poor lighting conditions.
 * Although framerate usually does not fluctuate much, the actual game speed (such as movement speed, enemy speed, and projectile 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 actually runs 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 are displayed at fullbright and thus "glow" in the dark (instead of just specific "bright" Things like Lost Souls or light source objects like lamps). Also, there is no real-time lighting from player gunshots.
 * Changes to the lighting engine also resulted in lessened depth perception due to the removal of depth shading. 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, the screen has a deep blue haze instead of a white one. Similarly, when taking damage or collecting items, the screen appears to momentarily flash blue, rather than red (for damage) or yellow (for items).
 * There is a minor bug related to vertical tiling of textures; all but one "tile" of the texture will be horizontally offset by one pixel, which can cause a slight visual disconnect in some surfaces with patterns or features that run the vertical length of the texture (such as SUPPORT3).
 * If two or more items are located in close proximity (roughly 32 units), 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. This bug is also present in the PlayStation version of Doom, and possibly other, earlier console 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 does not use 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. In terms of content, the game is nearly identical to the PC version, with only very minor changes. However, converting the gameplay and rendering functions to the Southpaw Engine resulted in a number of visual and mechanical inconsistencies from the original game; some are mostly cosmetic, but many more can have a significant (and usually detrimental) 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. It also has a noticeably higher rate of fire.
 * 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 Rifle 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.
 * The fist does not attack as rapidly; it has to return to the "idle" frame before punching again.
 * 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). It also features a much higher color depth than the version used in the GBA version of the original Doom, making it look more like the PC original.
 * The TL and TR faces do not appear when the player is attacked in the respective directions. The KILL face does not appear when the player holds down the fire button, and the OUCH face does not appear when the player takes more than 20 damage. The GOD face doesn't appear when the player gets an invulnerability powerup, but does appear while the player is using the god cheat.
 * The music tracks "Between Levels" (MAP04) and "Getting too tense" (MAP28) were dropped, most likely due to cart space, or the difficulty of successfully recreating them. 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.) Despite this, the blood on the Revenant's sprite is still red.
 * 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 some shots miss when they 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 can 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, presumably 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.
 * The bounding box of the Lost Soul's attack is much larger, 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. This 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.
 * The Former Commando's chaingun produces the same gunshot noise as the player's, rather than using the Shotgun's sound effect.
 * 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 angling the path of his projectiles), which usually causes his projectiles to miss badly. His third attack is performed more-or-less correctly.
 * 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 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 not counted towards the "Kills" tally at the end of the map. Only monsters killed directly by the player appear to be counted.
 * 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.
 * Weapon damage dealt to other players during Deathmatch is reduced by 75%, making Deathmatches much more protracted than usual.
 * The Armors 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, causing the player to suffer full damage from attacks. This happens until an item which affects armor value is picked up (either Armor, Megaarmor, a Megasphere, or an Armor bonus will work); this will "reboot" the armor system to properly protect the player again. If such an item is unavailable (or if the player can't collect the item because their current armor value is higher than what the item offers), the game plays as though the player had no armor. This bug has also been confirmed by Activision, the publisher.
 * The damage mitigated by Armor seems to be no more than 30%, regardless of which armor type the player has.
 * Even though the game runs on the Southpaw engine instead of the Doom engine, rendering errors such as Slime trails can still be found.
 * Instead of the story text screen being after MAP11 it was moved to MAP12.