Nice game, fun gameplay and cool soundtrack! Gameplay loop is simple but very engaging, works well. I would say I'm not a big fan of the art because of the inconsistent pixel size, but I know that's a matter of preference and many people don't bother too much. Also you probably don't need a "block of text"-kind of tutorial, especially for simple gameplay like this: glancing at the tutorial I thought the game would be compelx, but not at all!
All in all a fun game, keep it up!