If Super Stardust HD was Housemarque's twist on Robotron, then Resogun must be its Defender, right? It makes for a pleasing narrative: the hardware's moving forwards, but the Finnish arcade masters are clearly headed in the opposite direction, working their way ever deeper into Eugene Jarvis' cherished past.
The truth is a little more complex. Defender's handful of mechanics were shaken into vivid life by regular jolts of chaos as the flockers and the baiters wove mysterious paths through the scrolling levels. Resogun's 2D levels definitely scroll, you can shoot backwards and forwards, and you can even protect dinky, neon-green humans from abduction in between all the explosions, but Housemarque's enemies exist in a world of hectic predictability. They're zipping around in polite formations; they're warping in from Namco's galaxies rather than Williams'.
Just look at the finer detailing: Defender could offer you a nutty mechanic like a random hyperspace jump because it was fighting anarchy with anarchy. Resogun opts for a chainable boost instead - a calculated, educated risk for a game packed full of calculated, educated threats.