This is a fun, 4 star game. I don't like the way abilities cost gold, however. A separate resource system for spells/abilities (or just CD) would make it 5 stars.
It's a fun game, but.... I'm not paying to play, period. I think with the energy requirements per mission, I will lose interest, even though the concept is very cool. I quickly lose interest in games that sell power. Look at something like League of Legend's system of selling stuff for a better model.
 "Paladog"){kind=icon}
 "Monsters TD"){kind=icon}
 "Defender's Quest (lengthy!) Demo"){kind=icon}
 "Drillboid"){kind=icon}
 "Tyrant"){kind=icon}
 "Elona Shooter"){kind=icon}