The game controls/card placement is completely bugged and really bad! You would expect AT LEAST some quality on one of those ridiculous pay to play games...
It doesn't make sense the upgrade activation through charges in game. I can always activate them all without having a draw back in the charge consumption, it's not like I have to make a choice of either fire or update. I think this system would be interesting if there was any trade-off between choosing to spend your charges on upgrade or actually having to use them. The way it's made just makes the game boring until you actually hit further waves.
Not sure if this is a bug or if it is intended: When you put a gem in a tower or upgrade it, the cooldown before the gem is ready to fire can by bypassed by empowering this gem with an enhancement spell, such as the Bolt.
 "Midas' Gold Plus"){kind=icon}
 "Spellstone"){kind=icon}
 "Tesla8"){kind=icon}
 "GemCraft - Chasing Shadows"){kind=icon}
 "Doodle God Blitz"){kind=icon}
 "Bear in Super Action Adventure"){kind=icon}
 "Royal Squad"){kind=icon}
 "Jacksmith"){kind=icon}
 "Giants and Dwarves TD"){kind=icon}
 "Monster Arena"){kind=icon}
 "Zomgies 2"){kind=icon}