Thing types


 * Main article: Thing
 * For a single table containing all Things, see Thing types by number.

Doom, Doom II, Final Doom
These tables include the following columns.
 * Decimal - Type number, in decimal
 * Hex - Type number, in hexadecimal
 * Version - First Doom version that thing appears in:
 * S - Shareware
 * R - Registered
 * 2 - Doom II
 * Radius - Radius, in map units (note that the map "footprint" of a Thing is square, not round, so this is the distance from the center to the midpoint of an edge)
 * Sprite - First four letters of the name of all sprite graphics
 * Sequence - For animated sprites, default pattern through which the animation progresses. "+" indicates that certain gameplay developments (such as a monster being shot) may interrupt this pattern with additional graphics
 * Class:
 * A - Artifact item. Counts toward ITEMS percentage at the end of a level
 * P - Pickup. Player can pick the thing up by walking over it
 * W - Weapon
 * M - Monster. Counts towards kill percentage, hidden when using -nomonsters, respawns in Nightmare!
 * O - Obstacle. Players and monsters must walk around
 * ^ - Hangs from ceiling, or floats if a monster (aside from Commander Keen, who does not move; dead monsters, excepting Lost Souls, fall to the floor when killed)
 * Description

Artifact items

 * 1) Only one of these may be picked up per level, although any additional maps still count against the player's item tally. In multiplayer it is possible to pick another after dying and respawning.

Powerups

 * 1) Not picked up if the player's armor rating is at least 200%.
 * 2) Not picked up if the player's armor rating is at least 100%.
 * 3) Not picked up if the player's health rating is at least 100%.

Weapons

 * 1) Not picked up if the player already has one, and is already carrying the maximum amount of the corresponding ammo.
 * 2) Not picked up if the player already has one.

Ammunition

 * 1) Not picked up if the player is already carrying the maximum amount of this type of ammo.

Monsters

 * 1) Beginning with version 1.4, Lost Souls neither respawn nor count toward kill percentage.

Other
A certain number of additional objects (such as spawn cubes, rockets in flight, and Spider Mastermind corpses) may not be placed in a level at its outset, but are generated only during gameplay.
 * 1) No part of the final boss is considered a monster by the engine.
 * 2) BOSF is used for spawn cubes.
 * 3) FIRE is used when a spawn cube turns into a monster.
 * 4) TFOG is used while a teleporter is operational.

Trivia

 * There were several THINGS that were removed before the full public release. These Include:
 * A "Zapper"
 * An Office Chair
 * A Broken Lamp
 * Two lamps
 * Three Empty Barrel types (with Empty Nukeage Barrel, Brown Barrel and Grey Barrel)
 * A Rock Pillar (later used for the Inferno Sky)
 * An Unknown small "Step Pyramid"-esque object
 * A Small bush
 * A Small Cypress tree
 * A Marble Brazier
 * A Corpse burning in a Marble Brazier
 * A Pile of Corpses