Your grounded bool is bugged. When you leave a surface without jumping you can then jump in midair at any point. The UI buttons have their navigation turned on. So sometimes the Retry button counts as selected. So if you press Space to jump you trigger the retry function instead.
I got as far as the level after the tutorial was finished. There I couldn't figure out a way to activate the bottom bridge. I would have continued playing if I didn't find the various bugs too irritating.
The tutorial interrupted gameplay. It didn't tell you that you had to press Enter to continue the dialogue. The first time I didn't find out, so I clicked on Retry. You forgot to reset the playerControllable bool to true when you Retry, so the game effectively locks up. I eventually found out about the Enter key and was able to proceed. I found the narrative irritating, so I started skipping all of the dialogues. This led me to miss lots of important information. I would much prefer to have the relevant tutorials in the relevant areas. As your initial levels are tutorial levels, you could have embedded shorter text boxes into the levels themselves.
There was no audio at all.
The graphics are a bit of a mess. The level tilemap is using 2D assets, the character is a primitive square. The mana blast is a thing that looks like it's a UI asset. The exit IS a UI asset. The particle systems don't fit any of the styles.
I don't see how the game fits the theme.
A decent entry, with design potential, but too many execution problems for me to find it enjoyable.
Viewing post in You're a Mage jam comments
The various issues came from it being unfinished. If you read the games main page you'll see instructions that were not explained properly in the game. Thanks for the feedback though, I definitely found a lot of those functional issues after submitting it and playing it myself (overlooked them while testing for some reason). If you continue playing you'll also see how it fits into the theme.