I actually found Tower Wars to be pretty enjoyable (it's on Steam), but you pretty much need another person to play against, as its single-level SP training leaves much to be desired. It's designed from the ground up as a multiplayer game. --- "How do I get rid of a Trojan Horse?" -Sailor_Kakashi "Leave it outside the gates of Troy overnight." -Davel23
It's a non-traditional tower defense game but Dungeon Defenders is quite different. You have to run around to place the towers manually, you can attack the enemies with your own weapon (or spend your time/energy repairing and adding to your defenses), and each character plays a bit differently.
Out of the first four characters: The mage pretty much depends on his towers to do the most damage, the knight is kind of a mix of both. The ranger/archer chick has some traps rather than an actual tower (these will degrade over time) and the monk dude is mostly about fighting the monsters himself, but he uses various auras to weaken the enemies or replenish his health.
Best of all you're able to play it online with friends...
I don't know if you'd consider it "elegant" or "Simple" though --- http://raptr.com/badge/arleas/uc.png http://www.speedtest.net/result/2868545294.png