blue (game) has 50 levels. Each level is completely different from each other. On some levels, I'm not exactly sure what I did to fill the space all up with blue.
I solved all 50 levels in a few hours. I did consult the hints on maybe 5 levels.
https://apps.apple.com/app/blue-game/id1468076893
https://play.google.com/store/apps/details?id=air.com.bartbonte.blue
http://www.bontegames.com/
Other Bart Puzzles:
Factory Balls - excellent
Boo! - a mini sequel to Factory Balls
Blocky XMAS - fun and at times hard