This was a nice small game! I like that you make the flies so fast, because it really simulates how fast a frog has to be to react to flies around it. I almost felt like I was playing Kovaak's Aim Trainer. Now I'll be an aiming GOD in FPS games.
I think to sell the frog POV more you could have it so that a tongue shoots out from the bottom of the screen to wherever you click.