This is definitely the biggest surprise I've gotten all DD, didn't expect to like it as much as I did, and you implemented your mechanics really well. Here are some issues I encountered though.
At one point two zombies became immobilized since they were colliding against each other and moving in opposite directions, meaning neither could move anywhere.
I paused to write my notes, and the game restarted, very sad. Would instinctively press escape to get out of the shop menu just to return to the start of the game by accident. Very very sad, but i played through it again even when i was far in because i found the game fun.
I like when the bullets return to you, looks nice.
At first i thought i couldn't hurt the enemies because i'd hit them with the unaccelerated bullets and nothing happened. Took me a while to realize you could kill anything.
The dangling bits left behind by the eyes are annoying. They should only stop you while the eyes are alive. After you kill the eye, the dangle should move around when you pass it, but you should be able to easily walk through it. Like a one sided collision. I stopped playing because i couldn't pass the left eye dangle in the room where there's two of them with coins in the middle.
Was near a door while its power cut off, causing the door to stay open permanently.