A nice twist on the tower defense genre of puzzle-with-weapon gaming! Get the demo now for Defense Grid: The Awakening!
It's a lot deeper than almost any other TD genre game out there on the PC (this also is available for the Xbox 360). The graphics, smoke, music and sound effects provide for a much deeper experience.
Each alien has its own quirks, walking and running styles. The air units have a funky response as well - their flight patterns affect your defensive responsives.
You will be challenged once you complete the 8-12 hour storyline. Various types of custom setup (fixed resources, unlimited waves etc) that you can pit your TD skills at.
If you like TD, you'll love Defense Grid: The Awakening. Lots of replayability and much more immersive and intense than a plain jane flash game of old.
Check it out and try out the demo!