At first I don't even understand how power-up work, I thought fly and fly + shoot is just different power-up, get invincible come back down to finish the game.
I just wonder how is this game relate to the theme, then I read the description... "oh so the power-up can combine!?",
go back to play the game again, get fly + invincible and explore everything lol.
(I see a lot of place that need fly + invincible to reach, most of them can even go out of bound ...)