The basics: you drive around a track collecting gems into columns or rows of 3, and then scoring. The cool aspect? These tracks are dynamically created visualizations of any song you want.
Rough two-player co-op (one person uses mouse to control, one uses keyboard) also available.
Certainly worth it as the price of a McD’s meal.
Available through Steam. Sale ends sometime today. Possibly with the Heavy Update/Free TF2 weekend at 3pm CST.