On the surface this seems like a simple game, but by just looking closely at the interaction between three of the most basic offense upgrades: damage, attack speed, and impetus, things get incredible complex.
Any point invested in impetus (assuming the enemy is 10 meters away and rapid fire is active) is equivalent to .05[damage] x 2[attack speed] increase in maximum dps
Any point invested in damage (again assuming optimal conditions) is equivalent to ([damage up]+([damage up]x10[impetus])) x 2[attack speed] increase in maximum dps
Any point invested in attack speed is equivalent to .1([damage]+([damage]x10[impetus])
This kind of scaling makes it incredibly difficult and unintuitive as to which point to buy for maximum efficiency because the number you see increasing is only a vague clue as to what you are actually getting out of it.
It's pretty crappy that spells won't go off cooldown unless they are in the hotbar. What's the point in even having high cooldown spells at that point?
The ability to toggle wether you hero will attack anything in their path, or to go immediately to where you command them would be a nice funtion. It seems like they automatically ignore all hostiles when you give them the move command, unless you use their ability. Then they will move towards that location while attacking anything in their path.
 "The Perfect Tower"){kind=icon}
 "World's End Chapter 2"){kind=icon}
 "Mu Complex : Episode One"){kind=icon}
 "Nether Runner"){kind=icon}
 "Tesla: War Of Currents"){kind=icon}
 "Sentry Knight"){kind=icon}
 "Zos"){kind=icon}
 "a Grain of Truth"){kind=icon}
 "Kingdom Rush Frontiers"){kind=icon}
 "Socrates Jones: Pro Philosopher"){kind=icon}
 "How Smart Are You?"){kind=icon}
 "Giants and Dwarves TD"){kind=icon}
 "Liquid Measure 3"){kind=icon}