I like the idea and the interpretation of the theme (both 'physically close' and that relief when you nearly didn't manage to resolve a collision)! The art is adorable, and music's mood was great as well.
The controls are a bit glitchy for touchscreen as accidental multitouch causes planets to teleport, so I find the difficulty a bit high, especially for the speedy planets level. I'd also enjoy it more if I was not required to repeat every easier level in order to reach a later one, which would make practice much more effective. Still a cute little game overall!