Pretty good.
A good game. I like the graphics of the game. I do wish that there was some type of background music, though.
There were two main things that I didn't like. For example, that little popup asking to post your score got annoying really, really fast. Also, within the instruction section of the game, the arrows indicating the parts of the upgrade menu were jarring. They look like they were done in Paint while the rest of the game was well done. This type of thing makes the rest of the game lose some of its polish.