I was going to give it four stars, but I exited to check which puzzle I was on currently (had just completed cathedral), and it reset my progress to the first puzzle. That dropped the game to one star.
Upgrades should not be tied to the level being played. If you go back to an earlier board, you start with only what you had the first time you played that level. Almost all upgrade games allow you to replay earlier levels for extra xp and upgrade points.
There needs to be a limit on where the bad guys can go and still shoot you. Half the damage done is by shooters you can't see because they are not on the screen. Once on the screen, they shouldn't be able to run off it to hide.
it needs a 'give up' or 'quit battle' button for times when you mess up and there is no chance of winning. Upgraded catapult should fire faster and do more damage than it does.
It would be nice to have some control of the characters. All three that move chase bad guys to the edge of the screen, leaving the other side open for attack. Also, the money made by replaying a level should not go down so fast. I had to play most of the levels at least several times in order to get all of the upgrades.
 "Battalion: Ghosts"){kind=icon}
 "Not To Scale"){kind=icon}
 "Cursed Treasure: Don't Touch My Gems!"){kind=icon}
 "Hexagon"){kind=icon}
 "Nelly 2: ep.1"){kind=icon}
 "Sherlock's Assistant"){kind=icon}
 "Crazy Golf Cart 2"){kind=icon}
 "rocks vs gold 1.5 demo"){kind=icon}
 "Tesla Defense"){kind=icon}
 "Top Defense"){kind=icon}
 "The Tickler"){kind=icon}
 "The Great Siege"){kind=icon}
 "Angry Bird VS Green Pig-zombies"){kind=icon}
 "Zombie Situation"){kind=icon}
 "Amberial: Nebulosa Realms"){kind=icon}
 "MoneySeize"){kind=icon}
 "Ninja and Blind Girl 2"){kind=icon}
 "Deep Diver"){kind=icon}
 "Wreckanoid"){kind=icon}
 "the Game of Disorientation"){kind=icon}