Blood

Blood is ubiquituous in the Doom games, perhaps a large factor in making them controversial in some circles (and appealing in others).

In many levels, blood flows in rivers, over blood-falls, and gathers into pools. Standing in or moving through blood is usually detrimental to a player’s health (see damaging floor).

The Doom rendering engine creates animated blood spatter when a shootable thing is hit (including the player). Besides enhancing the atmosphere of the game, this helps a player to know that his aim was correct. Blood also splatters when things are crushed. For realism, hit inanimate objects, including barrels, produce a puff of smoke rather than a blood splatter.