Nice idea for this year's GGJ! But the execution kills a lot of the potential, sadly.
I'd recommend merging the buttons and the dispensers, since there's no need to keep them separate. A cleaner UI would help greatly with understanding the actual goal and game. For the gameplay, I'd show a preview of the next block that's about to spawn so the dispensers actually make sense. Right now, it's basically best to only use no. 2. Last but not least, make the phyiscs snappier to make the game "feel" better. Would love to play an improved version