Crushing ceiling

A crushing ceiling cycles between its starting height and eight units above its sector's floor. It damages both players and monsters that happen to be in-between. Barrels explode when crushed.

Crushing ceilings are started by specific linedef types. Once started, they remain running for the remainder of the level, even if temporarily suspended with a "stop" linedef type. No other ceiling action can be used in that sector thereafter. A stopped crusher can be restarted, but not changed, with any crusher "start" linedef.

A crusher can be either slow or fast. A slow crusher does more damage, simply by being applied longer. When a slow crusher is moving down and encounters something to crush, it slows down even more, by a factor of eight. This persists until it reaches the bottom of its stroke and starts upward again. Fast crushers do not slow down.

A crusher does 10 hit points of damage every 4/35 of a second, equivalent to 87.5 HP per second.

Crushing ceilings are listed as part of the "dangerous Doom environment" in the printed game booklets.

The Boom source port defines additional varieties of crushers.

Source

 * Boom source code: boomref.txt