Hexage's Robotek http://www.hexage.net/robotek/ reminds me that 'fighters' can be like micro versions of tower defense.
1. The attack medium ( whether Chi missile, laser, zombie bubble...) is the intrusive baddie coming thru your territory.
2. Your fighter is your tower. Maybe you're a Bot, maybe your a werewolf, or maybe an angry Tree -- your fighter gets upgrades and uses special powers to stop the ingress. Like a tower.
3. And you move into new defensible territories / levels after successful bouts with the baddies.
I guess there's a tendency to look backward and see TD, or the pollen of TD in earlier forms and genres... huh. Cool.
Sent from my Orac M-BRANE FieldTouch (Plus).