Fun game.
I liked the cute pixel art and the variety of upgrades and attacks available in the game.
Some improvement suggestions:
- It took me a while to identify that some zombies take more hits to kill than others. A health bar on the enemies would help.
- I didn't understand how to use special attacks until my third run or so. It would probably help if there was some sort of prompt to let the player know when they pick up an item that enables special attacks. "Special attack available!" with an arrow pointing to the attack slot or something like that.
I couldn't beat the boss but still felt like an interesting and fun game.
Good job!