NightSky reminded me of two great games...
In
Elasto Mania, players can compete for the
fastest time on each track. They can also save
replays of their runs. NightSky might benefit from such features.
In
Gish, players can play against each other in local
multiplayer. I think it would be fun to play some special levels in NightSky cooperatively. Versus multiplayer might be fun as well.
Overall, I don't like the light, minimalistic nature of NightSky (although I like the style) - I think the gameplay is solid enough for a more complex game.
By the way, NightSky also reminded me of
Ballance.