Tower defense is my favorite flavor of strategy games. Because it starts simple. The goal is clear. And the outcome is not binary - win or loose. Even your grandma will make some points if it's the first game she ever played. From there it's easy to learn and next thing you know you can't put it down.
My favorite TD has been "Defense Grid 2". It had all the qualities I described above. So this is the genre I picked when I decided to make my own game. I made a simple 2D browser game last year to test my concept (It's called Fold wars, you can play it in browser). From that experience I realized there are lot of unexplored mechanics in Tower Defense. So I decided to make a full fledged 3D tower defense game. And today I'm happy to publish the first alpha build for you to check out. It has only single level right now, but more will be coming soon. So far it has 4 kinds of towers, 3 kinds of enemy, and a little dymanic map twist. I've so many more things to implement, but they will be added in time. Please do give me your feedback till then.