I think it was the physics and the hitboxes mostly? The jumping and movement seem good on their own (especially the jumping, well done implementing different jumping strengths, that can be a tricky one) but you run into invisible walls sometimes and it's often unclear what exactly is safe and what will kill you. The unfrozen blocks can also be hard to control/predict in a way that feels unintentional. Again, super easily fixable after the jam if you wanna continue with the project (or implement it in a new project some day). Tons of potential here! I replayed the first couple levels to check on what I meant and still find the freezing mechanic fun to play around with. :P