Comment by AndrewOMartin

I always felt Deadly Rooms of Death (my preferred version being the free "Architect's Edition", but all are good, and many have better QoL features) was one of the puzzle games which was essentially "discovered" rather than invented.

Simple turn-based eight-direction grid movement, where one of your adjacent squares contains your "sword" and you can rotate your sword around yourself one square per-turn. Kill (deterministic and 1hp) monsters by moving your sword on to all the monsters move after your move, and "complete" a room by killing all monsters.

There's quite an active community (at least there was when I was in to it) but I've rarely heard it mentioned outside of the community.

Edit: I'm happy to see some other references to DroD in this thread.