Left and Right arrow keys flap you wings separately - your controls are sensitive, so you end up acting exactly like a moth.

Collecting rings increases your score, but also increases the gravity acting against you - your energy also depletes if you move a lot orr hit the walls, and if it reaches 0, you die!
The higher up you stay, the faster your energy regenerates - beware, however - don't hit the sun or, you will instantly die!