Amazingly fun game!
This is an awesome game. The graphics are great and the gameplay is really fun. Upgrading is awesome, especially when you get your turrets to around level 5 or 6 and you can start one-shotting stuff. There's a good amount of variety with the levels and different weapons. I've only beatent one campaign and I can't wait to play more. Nevermind the guy who said -1 for making a pay-to-play portion. This stuff takes a lot of time to make and I think we should appreciate the fact that we have a free portion at all! If you like it enough, pay a few bucks, and if not don't.
There does seem to be a bug with changing the selected cannon after doing upgrades and starting a level. It's like it won't let me select the last cannon I previously had selected until I click on a different cannon.