The player moves in response to the keyboard, mouse or joystick at either walking speed or running speed. The forward/backward speeds are somewhat higher than the sideways speed; these movements can be combined advantageously via [[straferunning]]. The maximum turning speed with the mouse may be adjusted by the user, although it may trigger [[Menu error with high mouse sensitivity|a bug]] in the menu system if set very high.
In a multiplayer game, the other players appear as marines in differently colored uniforms and [[armor]]. In the Doom games the colors are green, indigo (gray), brown, and red, although various [[source port]]s permit more choices of color, and sometimes more than four players in a game. The [[sprite]]s for a player are rendered in a green suit; to draw another player, the [[Doom rendering engine|rendering engine]] remaps the shades of green to shades of the corresponding color.
A player spawns with 100% health, a [[pistol]], and 50 bullets. The [[fist]]s may also be used as a weapon. In [[Hexen]], on the other hand, the player's attributes depend on the chosen character class. When respawning after being killed, all acquired [[item]]s (such as [[armor]], non-default weapons, [[ammo]], [[power-up]]s, and [[keys]]) is lost. In [[deathmatch]] mode, one exception is made to this, as players always spawn with all the keys.
In order to be playable in single player mode, a level must have a player 1 start [[thing]], and player starts 2 through 4, typically located close by, will enable [[cooperative]] play. [[Deathmatch start]] positions are usually located far from each other, and one is chosen at random each time a player spawns. The absence of player starts will cause a single player or cooperative game to [[Player starts missing|crash]], and a deathmatch game to exit with an [[error message]].