The first thing that struck me was the art, the color pallet and the cute animations!
I had to restart the game few times because I got stuck on the wall with the belt pushing on me the block and you just get stuck in the wall and have to restart from start :D, but other than that, the game feels polished, movements a bit floaty but other than that the idea is really nice! Maybe make it so we can add and remove the modifiers with clicking instead of dragging. Also would be nice to have a "tab" button to open up a little inventory of your modifiers, or have physical small blocks added to the character or something in between like little colorful particles that floats around the character like the key.
Plus when I got stuck I just left it, and left to get something to eat, came back and started working, with the music playing in the background for a good 30 min before I realized it's been an hour, send help. So the music is also very nice! Loved playing it! Great job.