Very fun, this has a lot of potential. The controls feel really fluid and the game is very bright and colourful so it looks and feels great. I was also impressed with the bonus stages they a nice touch, on the paint one a % would've been nice to see how close I got to total completion. Maybe even a specific bonus stage only mode to try and set high scores or some sort of WarioWare style minigame mashup could be interesting.
I didn't play 2 player but can you play the bonus stages in that too? Competing for more paint coverage like Splatoon and maybe a top vs bottom Pong style ball battle could be fun. Best of luck for development!