Thanks for the feedback! Glad you liked it. I'll probably take a short break before continuing with it, but I do plan on continuing with it; there's a variety of stuff I just didn't have the time to get to. The basic idea for the game is one I've had lurking around the back of my mind for some time now.
The game's definitely a bit RNG heavy at the moment; my own test runs have so far been heavily dependant on how many healing potions turn up, especially on the lower levels.
The mutations system certainly has room for improvement; aside from what you noticed, its also possible for a mutation potion to, for example, give you "bat wings" then immediately overwrite it with "feathery wings". Probably also worth making some mutations more common than others and making them overall more impactful.
I'll probably just remove ESC on the main menu quitting the game; it should be easy enough to cursor down to "quit" to not be necessary and, while I didn't mention it anywhere, many of the game's menus (including the main menu) can be controlled with the mouse as well.