Official application description:
Something exciting and new in the Tower Defense genre! The geometric vector creeps are fast and intense. With 30 different maps, each its own puzzle, you'll have to work fast to keep up.
Using exciting vectorized graphics, this highly kinetic game brings a whole new dimension to the tower defense genre. Devastate creeps with blasters, lasers and missiles and watch their energy debris swirl through the gravity wells of your vortex towers. Now it's time to figure out how to put that absorbed energy to good use...
With the ability to compete for the high score with friends on the leaderboards and exclusive Xbox LIVE achievements, this is a tower defense game like no other!
geodefense is a critically acclaimed game and having played this on iOS, it's worth the price along with XBL achievements. I should add one thing though, geodefense II is under works so you can probably imagine that most of the ' rock star ' developers don't see WP7 as their first priority. Hope that changes with time. Anyways, if you are a tower defense style game fan, this is a must download for $2.99.
Zune download link