I love:
- the name
- the assets (the unicorn omg <3)
- how different colors have different properties (a lot of potential on this one, imagine e.g. sticky - can roll on vertically or upside-down, glass/viscous slows down bullet but doesn't stop it, ....)
- the level design slowly introducing how to solve different levels
- the "history of last delted stroke" (there could be even more of them in different intensities)
- the cute 2D in 3D inclusion
- very accessible controls with keyboard
Some things felt a bit rough around the edges (e.g. post its could be removed after the first level to not clutter the canvas, camera could be zommed out a bit, particle effects on drawing could be smaller, so I can see what I am drawing - or was hiding that intended?, physics behave differently in subsequent runs, and of course one or the other bug, not being able to restart properly is particularly annoying), but I like this entry a lot and it also reminds me a lot of the old "Line Rider", good times! :D