how do you defeat the mantis "boss"? i still have/had version 0.34, is it even possible there?
If you don't have any shoes left, things will be very hard.
When he charges at you, run diagonally away from him. When he stops, shoot his head no more than two times before running again.
Firing your last shot will recharge 1 shot faster than normal, but leave you unable to move for multiple seconds. This strategy is not recommended for boss fights. Take your time instead. His HP does not recharge.