Pretty cool game! I loved the little flavor text and the changing appearance of the main character as you gained more powers. The movement felt a bit slow compared to the size of the level, and the controls were pretty slidey and unresponsive at times, especially around slopes. I have to say the spikes one-shotting you was pretty frustrating.
I quite enjoyed the music, and some of the artwork was really pretty, especially for the various paintings and decorations around the level. However, the level itself felt a bit thrown together at random and was hard to navigate. A more robust savepoint system would have been nice, as some of the runbacks after death were a bit annoying, especially when the instadeath spikes were involved.
On a more technical side, the web build didn't play so well due to the game not scaling up to the full screen and the gamepad support not working very well (every button seemingly being registered as "attack," though that could be a problem specifically with my third-party Nintendo gamepad). The desktop build worked much better, though I still ended up using the keyboard in the end due to the left stick input being too sensitive at detecting up/down movement and not being able to use the d-pad.
The goat boss was by far the hardest due to its constant running back and forth (and lacking max health upgrades at that point in the game). All of the others were solved by just standing next to them and attacking. However, I did like the ending of the game a lot, and the background art of the castle was really pretty. Overall, good job!