Bizarre Creations decided not to put Geometry Wars Waves on Xbox Live Arcade because it's just a fun little extra.
Waves can be accessed through your garage in Project Gotham Racing 4. It's the same two-stick shooter of old, except enemies attack in lines at different angles, which ramps up the difficulty but richly rewards those of you who can manoeuvre deftly in tight confines.
Anyway, during a recent studio tour we asked whether the reason it wasn't coming to Live Arcade was because it might annoy Sierra, with whom Bizarre is making Wii and DS title Geometry Wars Galaxies.
"It's because we had plans for Live Arcade, but Waves isn't it," community and web lead Ben Ward told us.
"Waves is just a sort of throwback to where Geometry Wars came from originally - it's an Easter Egg in a game, it's one game mode, it's something that you'll play again and again to beat your high score, but it's not a full retail product."
Design manager Gareth Wilson chimed in: "I think as well that Geometry Wars as an IP has outgrown Gotham, and it's almost a little bit odd to put a full blown version of Geometry Wars in PGR because it's actually bigger than a mini-game now.
"So we put Waves in because it's a good laugh, but it's left the nest really."
And the top Bizarre score is around 50 million at the moment, apparently, so you'd best get to sharpening your thumbs.