What a neat little tactics game! I was disappointed to find that pushing enemies off ledges softlocks the game, but I really liked getting the three little dudes working together nonetheless.
Thanks for reporting this bug!! As of v1.1.0, it has been fixed it so units now die when pushed off the map.
The original intended behavior was that units would never be pushed off the map, that they'd collide with the edge of the map. But isn't it way cooler to yeet your enemies off the map??