You can see the controls in the game when you click on the icon on the right hand side.
You can move with WASD while you swing to control yourself a bit.
I think that's why you had problems gathering the 50 flys, since the first 2 levels are the easiest part of the game.
But the last 2 stages are actually hard though.
Let me know if there's anything else you've trouble with.
Thanks for playing!