The Pixel Review writes:
If you’ve been remotely cognizant during the last few years, you’ve at least heard of the popular Tower Defense style of games (Pixel Junk Monsters, Plants vs Zombies, etcetera). If you’re the type to apply labels to things, you could very accurately label Orcs Must Die a Tower Defense game as well.
You play an apprentice Warmage, a vocation that serves as humanity’s last hope against the Orc legion. Equipped with spells that ultimately function as traps, you must face insurmountable odds as hordes of Orcs bumrush the ever important rift.