only apparently simple
Yeah, a lot of tower defense games out there, but this is nice. nothing really original, but a excellent proposal of classical td elements, and great graphic! i hope there will be a sequel.
The skill tree system isn't perfect, though...
The undead skill tree is unbalanced; mana stock is the weakest of the entry level skills, but almost all the remaining are horribly overpowered.
The Demonic skill tree has a good entry level skill, but after basic training you don't unlock anything useful; advanced skills as return portal are better but it takes a lot of wasted skill points to get this far.
The orchish skill tree has really useful skill until you get marksmanship. Remaining are not bad, but nothing compared to undead abilities.