I left a previous comment (now deleted) that killing enemies doesn't work but I think that was just an issue on my part. Anyways, I quite liked it, I found it a bit difficult and I would've liked for the enemies to back off a little after damaging the player to avoid draining all the health in under a second. Some more visual feedback like screen shake for recoil or flashing red for taking damage would've been cool to add with extra time, and also music and sound effects would be cool. But overall good game!