Very nice game. Some possible optimizations: Making the combat a bit faster would be nice. I'd rather gain oxygen geometrically instead of gaining 1 per N time, so for example make it start at 1 per N, but then increase faster and faster if I don't move ore aren't attacked.
Some UI issues, buttons not showing properly on screen, my power disappearing when dropping down, horrible continue font (unlike the awesome intro white with black shadow font at the start).
But overall a great effort.