Great game! Not much to it, but everything here is solid and feels really good. It took me more than a few minutes (maybe 10), but I felt like I had to beat it before I put it down. That's a good thing!
Maybe it would be cool to have red & white shields along with the yellow. That could lead to some interesting dynamics!
The only negative I have with this game is the sound. The sound effects you have are good, but it seems like there should be a little more (not a lot) going on in the soundscape.