Hmm.... Well done. I like it.
A few things to possibly fix however:
1)The Lights of the stars disappears already when going from night to day, the stars themselves you can see, but their lights are off.
2)Why not dim the light/darkness in one flow? Now you have like, four 'degrees' of darkness, but you could simply subtract some from the light every frame until you have night, and then add the same number every frame again to regain light. This would make it seem more natural.
3)It would awesome to see the light of the stars earlier in the evening. It is quite strange now that you only see the light in the darkest of the night. That is not right.(wow, a poem xD)
4)The Moving Platforms seemed to move much slower while reading the sign.
5)I know you can airjump, but you can jump even another time when you've fallen a bit down, but are still in the air.
6)Mozilla had difficulties displaying the Applet correctly without F11(fullscreen page mode) on. I missed some bit of the bottom. I don't know if this is a error from you however