This so close to being good, but it's just not good. Yet.
1. The font for the upgrades is unreadable. Change it to a standard font.
2. Get rid of the red ones. It's impossible to miss them sometimes without letting a green one thru. The red one should GIVE you a life when they get thru. That would make it worth missing a green one.
3. Reset the ball faster, and set it that if the power is 0 then the ball doesn't shoot until the next click is registered. Often, I'd click before the green ball was off the screen, so when the new one showed up, the computer registered me having already clicked, but wouldn't grow my power. Once I release the mouse button, the ball just falls straight down. If I'd clicked again, the next one does the same thing.
4 Add a NEXT button after each level. The game says it's paused, but it's not. When I get to the upgrade screen, the squares start coming anyway.
5. Give me more lives! 3 balls/lives? That makes the game too quick. Every game is all of level 1 and part of level2. That's it. Give me 20 so I can take some damage and still keep playing.
6. The words that come up in the background fade out too fast. It's difficult or impossible to read them before they go away; especially if enemies are coming and you have to look at them.
The music is good. The idea for the game is good. The graphics are good. There are just some things that aren't right yet.