Its playable and understandable but its boring and ugly.

It's a little bad you weren't motivated to do more, because the idea of the game itself isn't bad, but the result here is not good. What you say in your comment (sounds, music, levels with blocks and powerups) would improve greatly the game. Telling controls would be welcome (arrows, wasd or both)

Different backgrounds could be good (and different sprites for balls? Imagine fireballs in a volcano level for example).

Making crouch your character would be helpful in some cases against the army of balls.

I rate your game only 1 star for your lack of motivation, the game doesn't look finished, something is missing. Be motivated next time!

Was quite entertaining. I enjoyed it for a good 15 minutes.