Thanks for playing my game!
Powerup strength could definitely use some tuning, I agree. And for enemies, I actually have a really neat spawn director system that can ‘purchase’ units based on their strength value, and its budget goes up over time and stuff – everything I need to handle spawning more difficult enemies as time goes on and as you kill more and more. The only problem is I didn’t get around to adding more than one enemy type!
You can actually see the SpawnDirector talking in the javascript console… I forgot to turn off its debug text :D