good game, solid controls, the only downside is the difficulty, it is quite easy. even the final boss swarm they never got close at all.
i do like that the game allows you to have 3 different kinds of upgradable units, each with a unique tree, but the splash damage unites were so powerful that i used nothing but them and nothing ever got close in any level.
2 pushbacks and a stun makes enemies never enter the screen
2 stuns and 1 pushback was good for swarms
3 stuns destroyed bosses within 30 seconds. if fully upgraded.
you made a good game, and i would like to see more from you.