Tripbombs can be placed on a flat vertical surface. Once placed, they emit a red laser beam. If any players or enemies are dumb enough to walk into this beam, the tripbomb will explode.

Place a TRIPBOMB (#2566) on a flat vertical surface. It is oversized by default, but the size will have no effect in-game (you can resize it if it bothers you). Approximately two seconds after a tripbomb "sees" the player, a red beam will shoot out and the tripbomb will be active. The tripbomb itself is the source of the explosion, thus it is possible to avoid the explosion's range simply by tripping the beam from a distance. Also, the laser beam itself is actually a collection of sprites, and these sprites are limited to a certain distance before being cut short. For these reasons, you should limit the distance that the beam has to travel to reach another wall.

Notes:

• The beam will be triggered if a player, enemy, or moving sector disturbs it.
• The beam is also triggered by clipping abnormalities, which can occur in very large sectors with long walls.
• The beam will be reflected in mirrors, and tripbombs can even be placed on a mirror. Surprisingly, the explosion of an attached tripbomb will not destroy a mirror!

I've never seen this done before, but the MORTER (#1650) is absolutely perfect for a proximity mine. The mortar shell sprite is compatible with resizing and virtually all cstat flags: palettes, transparency, flipping, relative alignment, true-centering, etc. Floor-alignment will fracture the texture, though.