Just some quick initial points (non-gameplay, but more menu flow) on UX elements:
- Think about making the initial post-install cold-opened tutorial skippable. I'm not sure if it was just me (running on Mac OSX 10.11.6), but I felt constrained to it and was unable to open any in-game menu to either just check or exit out of it. Could come up as an issue when re-installing and forcing players through it again. Suggestions either allow the main/pause menu to be accessible right away, or just open right to the main menu with the tutorial pre-selected so all the user has to do is hit go. Users don't like being forced to sit through stuff.
- During game over, allow users to just hit space to restart a run immediately (think about the death flow in super meat boy). Users will die a lot in this game - make the game over screen less punishing and more like something they can gloss over and restart immediately. Think like the game over screen in binding of isaac - it takes less than a second to start a new run.
One other point, aside from UI elements, is that I was surprised that fire didn't hurt me - I kind of expected it to. That might be for the best, but I'm a heavy binding of isaac player, so I guess my expectations are generally based off of that.
I tend to be picky about being forced to sit through timed UI elements, so stuff like this is what I immediately notice. I'm continuing to enjoy the game though, and I'm getting better at it each time I play. You guys rock.