Nice concept! I wish there was some background music to go with it. The result feels a bit austere.^^
The puzzle are indeed really open-ended, and overall pretty easy. Only the last one required some reflection (although it didn't accept my solution). Also I'm don't really understand what's on the bottom right of the screen, and if it is useful for the puzzle resolution. But besides that, and the controls that are indeed slippery, the game works pretty well. The visuals are clean, and the levels are short enough to be appreciated. And it's nice to see a game combine two different interpretation of the theme!