Great game, I wasn't sure what the upgrades were and the first time I thought the game has crashed! A little text to display what the upgrades did and perhaps a little movement on screen to make it look like it's not a crash would have been cool!

But I like it! It's a great entry :)

Nice background movement.

Really satisfying gameplay!

Good game, I would have added at least a quick text info on the power-up though. Nice parallax effect on the background!

The art and the way the enemies attack differently is great implementation! Keep up the great work!