Doom for Game Boy Advance

Doom for the Game Boy Advance was released by David A. Palmer Productions on October 26, 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. It was followed in 2002 by an independently produced version of Doom II.

Differences from PC
Most differences from the PC version are directly inherited from the Jaguar version of the game on which this port is based.

Maps
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. This includes several bugs directly inherited with these designs. As in the Jaguar version, no maps from Episode 4: Thy Flesh Consumed are present, as that version was created before the expansion episode's 1995 release.

The only secret level remaining is.

Individual map changes
All of these changes are inherited from the Jaguar version:
 * About half of has been removed. A few rooms remain which are inaccessible, and as a result, 100% secrets cannot be obtained on this level. The Sony PlayStation version of this map is the only one which fixes this error.
 * Part of was taken out.
 * is significantly different.
 * is replaced with, though it retains its original title here.
 * is replaced with the totally different.
 * is not present.
 * Large portions of are removed to control line of sight and scene complexity.
 * is not present.

Mechanics

 * There are no crushing ceilings.
 * The blur artifact and light amplification visor powerups are removed entirely.
 * Health potions and spiritual armor give 2% instead of 1%.
 * 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.
 * No animated or text intermissions appear for the first two episodes' completion; the only intermission that appears is at the end of the game.
 * 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.

Monsters
Neither cyberdemons nor spiderdemons are present. Barons of hell and cacodemons are typically used as bosses instead, with the game ending on the equivalent of E2M9: Fortress of Mystery, which as in the Jaguar version is retitled Dis.

Spectres are situationally either removed or replaced with demons.

Cacodemons move much faster than normal.

Episodes
The game features an episode select screen like the original PC version, but the game itself is not actually divided up into episodes, and has no episode end 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 select" function, allowing the player to start from later maps without having to play through earlier maps to reach them.

Graphics
The status bar is completely redesigned to be drawn via the Game Boy Advance's tile layer system. It more closely resembles the original PC status bar with a concrete-based texture, uses different fonts, has no percent signs, and lacks the "Arms" weapon display entirely.

Censorship
Along with it sequel, this game is notable for being heavily censored in order to obtain a "Teen" rating from the, as the first party console manufacturer discouraged creation of mature-rated games for the platform, focusing its marketing heavily on the  demographic. All blood is green, both for monsters and 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. Monster corpses vanish after a few seconds, and there are no gib deaths. Some impaled and hanging corpses are also removed.

When taking damage or collecting items, the screen appears to momentarily flash blue, rather than red for damage or yellow for items.

The ending intermission was modified. Episode 4's ending screen appears instead of the infamous shocking "bunny" ending.

Mechanics

 * The demon's death sound is replaced with the imp's death sound, in order to save ROM space.
 * Ultra-Violence mode is renamed "Nightmare"; true Nightmare mode was removed altogether.
 * Collecting an invincibility power-up gives the screen a deep blue haze rather than use of an inverted black and white scheme, presumably to maintain visibility.
 * A "static lighting" option was added, which renders all sectors at full brightness. This was provided for performance reasons, as well as because of difficulties with the first-generation Game Boy Advance's dark unlit display, as the frame rate notably increases when the light calculation code is skipped.
 * 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 needed to render them, as well as decreased available color depth on the display.

Music
Unlike the Jaguar version, Doom for Game Boy Advance features a full soundtrack both during gameplay and intermissions. All music is shifted ahead - E1M1 uses E1M2's music, E1M2 uses E1M3's music, and so forth, until E3M3 is reached. Most tracks are significantly simplified, and some have been creatively remixed in an effort to make them sound better on the GBA's limited sound hardware.

The box of bullets is a brighter shade of green.

Saving
Game progress can be saved between levels. There are four save slots available to use. Saving requires changing the answer to the "Save Progress?" question to "Yes" and confirming, and then selecting a slot. A second question must then again be answered "Yes" to confirm overwriting the save file. Unlike in the PC version of the game, a save cannot be named, and will instead be automatically named for the level number reached on that save slot.

As a possible bug, the game does not prompt the player to save upon entering the E1M9 secret map. It must therefore be completed in the same session it is entered.

Bugs

 * 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.
 * When the player drops off a high ledge, he makes the pain sound instead of the usual "oof" sound, even though that sound is still present for pressing unusable linedefs.
 * Punching walls and inanimate objects produces the same impact sound effect as punching a monster.
 * A bug makes palette index 0 transparent, even in contexts where it should not be.
 * 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.
 * The "You are here" indicator on intermission screens often does not point at the correct location; this is particularly true for Episode 3, where the locations do not correspond to the background graphic in any discernable fashion.

Multiplayer
Like the Jaguar, the Game Boy Advance game supports multiplayer gameplay for two to four players via the or. A cartridge and system are required for every player joining the game; there is no upload-based limited play feature.

The GBA version of Doom also comes with eight brand new deathmatch-only 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. These levels have so far not been released on any other system. Their author is presently unknown.

Weapons

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

Enemies

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