Nice work
Nice game :)
Some ideas for the future, difficulty settings: speed of attackers, rate of attacks per minute, durability of victims thrown, broken legs on thrown victims that survive that makes them run slower etc.
Sound any good? :)
Also, can you build more stuff in the castle? Such as wizard-school=wizards on your towers that shoot lightning and fire, ballista-range (big arrows at interval) and maybe a possible superattack that could wipe all enemies on screen for say one every 5 levels recharge.
It's very addictive but also very frustrating at higher levels, hehe.
Great work man.