While not a great game, I still found this to be good. I think it's mostly because of how it's interesting to see how the upgrades get better. It doesn't seem like much at first, but it does get more interesting. I appreciate how it's done in a simple manner, but is still complicated. You have little idea what enemy is going to show up next.
But yeah, it does take awhile for it to get really good. It's still worth playing. I like collecting all the little white pieces. Sometimes I'm too busy doing that to even pay attention to shooting the enemies. Automatic works the best as expected.