Fun idea! It reminds me of my favourite Nitrome game where you draw a path for ants to move forward. (I think it was called "Scribble")
The drawing sound is satisfying and the rainbow you draw looks great too! Music is goofy and fits the overall vibe of the game. I also like how you can see the next direction of gravity, kind of like seeing the next block you'll get in tetris.
The only con I can think of is the lack of any progression. Maybe I was too bad to survive long but I think it's basically the same difficulty the whole time? For my taste it could have been easier to start with and then gotten harder over time. Maybe the spikes on the floor and ceiling could only appear after a while or something?
Very solid sound, visuals and game idea. I wouldn't be surprised if this game wins the jam.