Well I feel obligated to write a bug report here. I was playing the game in browser, with a keyboard.
The game sometimes doesn't pause when picking upgrades.
Enemies are spawning out of bounds in the pit level.
Random lag spikes.
Also not really a bug, but on keyboard you have to navigate the menus with arrow keys while everything else uses WASD, which is a bit weird.
Other than these, great game, creative idea.