Really cool spells! I especially liked the orange one that spawned falling blocks! Unfortunately, I got through the tutorial room and then the game didn't progress afterward, it was stuck on a black screen. But from what I did play, there was quite a lot of content! You had 6 different spells and various enemies which is definitely a lot to pull off in just 7 days, so congrats!
I would say my feedback is similar to what others have said! Mostly just the slippery movement and the large amounts of knockback. I also found that some spells felt unbalanced, but that's to be expected for a jam. Going forward, you could probably increase the damage output for some of the spells like the bomb since that one has like a "wind up" time and is difficult to aim upwards. I would say adjust the damage output and such based on how easy it is to actually use the spell or something like that.
Overall, really cool idea and very fitting for the jam! I personally found the controls to be fine, but I guess it's subjective. Congrats!