This is brilliant! My favourite that I've played from the jam so far.
The core mechanic is fun and well-executed. The sound and visuals support it perfectly. I love how the enemies shift between hurting you and being your only hope of recovering from a mistake. I found myself wishing for an in-level restart, but not having one is what forced me to play through setbacks and actually helped the game to shine.
Enemy formations and movement patterns are varied well, and blocks with interesting new mechanics are introduced at just the right times.
My only real complaint is that I occasionally just had to watch the timer elapse on a promising run while I waited passively for the right block to appear. But even this, I hesitate to criticise, because it encourages you to make a tricky lunge for a block that's coming in at the wrong angle.
Overall, I love it. I would definitely consider buying a full-game version. Thanks for sharing it with us!