The surest sign that a company is running out of ideas is when it starts repeating itself. Ristar, which features a spunky, diminutive hero with oversize tennis shoes, is a shameless recycling of Sonic the Hedgehog, right down to the older game’s candy-colored scenery and hop-and-bop action. But as with many clones, there’s a certain clever degradation involved: Whereas Sonic’s forte was a harmless-looking spin-jump, Ristar head-butts his enemies like a Cockney thug. B-