Grid Wars, by Mark Incitti, is a freeware game for PC and Mac. It is, as the alert viewers of WoS will instantly recognise, not unlike Geometry Wars, the secret bonus game concealed within Project Gotham Racing 2 for the Xbox.
In itself that'd be passingly interesting - particularly for anyone who didn't want to fork out £300 for a state-of-the-art, all-singing, all-dancing Xbox 360 in order to play a vector-graphics Robotron game - but while GW2 is undeniably closely related to GW:RE, it's the ways in which it's different that make it remarkable. Remarkable, in fact, to the extent that it's possibly the single most perfect piece of pure videogame design that this reporter has seen in the last decade.