Anomaly Defenders is now available through Steam and Games Republic for $9.99. This time the tower defense/offense/whatever sees you playing as the aliens, defending their homeworld from humans looking for revenge.
This also apparently marks the final chapter in the Anomaly series, which is kind of a bummer. I've always enjoyed these games in short bursts when I needed a break from something. Anomaly Defenders will also be coming out on iOS and Android, which is the version I'm waiting for myself.