Nice little game but boring.

You can add some things to make it more interesting. Have the different colored enemies have different behaviours/attacks.

You can make them move in patterns, shoot at you, charge at you, etc. Also add different guns: pistol (default), shotgun, machinegun, etc. Keep the cooldown bar on the right, I like it.

Make use of the death animation. For example, each enemy of a given color explodes with the same color explosion. All enemies of the same color near the explosion also get killed. This way you can try to chain enemies together to make them explode. This way you will be combining that match 3 game with a top-down shooter.

Keep up the good work!

This is pretty fun. 

Nice simple game. bullets definately need to be fast. Power ups would make me want to play for longer too. I love to kill multiple little coloured balls with a flame thrower :) 

It's a cute game and the death effect of the enemies looks really good. You could make bullets a bit faster and maybe add a few extra mechanics because it's a bit too simple for my taste