Doom for Game Boy Advance

Doom for the Game Boy Advance was released by David A. Palmer Productions in 2001. It is based on the Atari Jaguar version of the engine used for the first series of console ports developed during the 1990s. Its game play is generally true to the PC original, albeit with less overall content.

Differences
The game has 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:


 * All maps in the game are simplified levels based on those used in Jaguar Doom, with less complex geometry, fewer textures used, and some areas removed (also, including some legacy bugs from those designs, enumerated below).
 * No maps from Episode 4: Thy Flesh Consumed are used--all maps used are (simplified) adaptations of episode 1-3 maps featured in the Jaguar port.
 * Although the game features an episode select screen like the original PC version, the game itself is not actually divided up into episodes (and, as detailed further below, has no episode transition screens). Instead, the game is set up as one continuous episode; 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 without having to play through earlier maps to reach them.
 * Neither cyberdemons nor spiderdemons are present. Barons of hell and cacodemons are typically used as bosses instead.
 * 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.
 * Slightly different status bar, which uses different fonts, no percent signs, and lacks the total weapon display through numbers.
 * 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). Also, its color depth is noticeably lower than in other versions of the game, resulting in less detail. Some face expressions are taken from the Jaguar version.
 * Sound propagation 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 propagation 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.
 * No animated or text intermissions appear for the first two episodes' completion; the only intermission that appears is at the end of the game. Also, the ending intermission was modified; episode 4's ending screen appears instead of the famous "bunny" ending (probably to avoid an M rating).
 * 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(s) will disappear at the same time the first message was supposed to disappear, occasionally making them near-impossible to read.
 * 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).
 * The demon's death sound is replaced with the imp's 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.
 * A "static lighting" option was added, which renders all sectors at full brightness. 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 real-world 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). Note also that this option may have been used to justify the removal of the light amplification visor from this version of the game, as enabling this option renders the usage of this power-up redundant.
 * 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 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 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, rather than the colors going black and white, the screen has a deep blue haze. 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).
 * 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 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