Fragility Floor is a floor type, like Hot Tiles or doors.
If an entity is on the Fragility Floor, it becomes "
fragile"
.
If an entity A tries to move into an entity _of a different type_ B that is on a Fragility Floor, A moves onto that tile and B dies. So if Beethro tries to move onto a roach on a Fragility Floor, Beethro steps onto the roach and kills it. If Beethro is on a Fragility Floor and a mimic tries to move into Beethro, the mimic steps on Beethro and kills him. But if two tar babies are on Fragility Floor, a tar baby can't move onto a tar baby to kill it (and a mimic can't move into a mimic, a goblin can't move into a goblin, etc.)
If a weapon of any type (even a pushing weapon) moves onto an entity on Fragility Floor, it is killed.
Invulnerable entities like Wubbas/Gentryii/rock golem corpses on Fragility Floor can either be stabbed or step-killed; stepping on a Gentryii chain acts as though you cut off the chain at that tile. Snakes can be stepped into or stabbed on any of their parts to shorten them; stepping onto their tail both shortens the tail and frees up the space for the attacking entity to step into, and if the snake was 2 tiles long then stepping onto its head shortens it to death and frees up the space to step into.
If tarstuff or fluff grows onto a Fragility floor, those floor tiles are never considered stable / part of a valid 2x2, so those tiles grown onto always produce babies where possible. Similarly, if any tile of a Rock Giant steps onto a Fragility Floor, the entire giant decomposes into its four Rock Golems.
If an orb is on a Fragility Floor, it can be hit with a weapon or bumped into by any entity to activate it, and then the orb cracks. A cracked orb can be bumped into to activate it and make it crumbly, and a crumbly orb can be stepped onto and destroyed completely.
Similarly, a bomb, keg or mirror on Fragility Floor can be hit with a weapon or stepped onto and immediately detonated/smashed.
If fuse is laid across Fragility Floor then it can be lit by stepping on any tile, not just on a fuse end. (maybe monsters can do this too, not just Beethro/doubles?)
There are also probably other interactions that would make sense too.
Finally it might be convenient to be able to turn Fragility Floor on/off via orbs or pressure plates but that's more of a stretch.
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