Amazing game idea. Most people already said but adding some lines to clearly define what is the death area of the laser would be nice. Also got to give it to you, loved the sound effects.
PS: One thing you add just to add a bit more fun and complexity would be that the monsters would be death on the laser path, meaning the death body sprite would be left behind. So you would have to send someone to clean the bodies, but be careful you do not want to kill the janitor who is cleaning the bodies from the gates way :)