Pretty good for a 2$ game
For a $2 game, it's a very good game. A simple "pick-and-play" game like in the SNES days. You can even play it with two players simultaneously (co-op mode)! The graphics do the job and the music is OK. Controls are pretty good, but there's no button remapping possible.
The game is extremely short: around 3 hours to finish it. I advise you to choose the "hard" mode because the "normal" mode is very easy.
It's a bit sad that the developers didn't invest a little more time to refine the game further. Very little variety of enemies, the various level designs are overall a bit dull/boring and the map on which you select a level looks very cheaply made. But regardless, I had a good time during the 3 hours that the game lasted.