We know a good ass thing when we see it, and Chance the Rapper’s new song and video, “Good Ass Intro,” is accurately named indeed. First of all, consider the star of the show: This Chicago youngster was a shoo-in for SPINs’ Hottest MCs in the Game list what with his fluidly off-kilter sing-song delivery and ungated gush of topical inspiration. Next consider the guests. John Legend actually contributes, and that’s good for the headlines, but so does BJ the Chicago Kid — the fresh Motown signee recently seen in our Best R&B of 2013 preview. And then consider the clip itself: a tie-dye merging of animation and film footage that recasts Chance’s oft-dancing silhouette (see his super endearing “Juice” video) as one of Keith Haring’s eternally bopping 2-D Colorforms. Sure, the Rapper’s April 30 album is called Acid Raps, but this seems like a celebration of life more than an exercise in drug advocacy. Stefan Ponce and Peter Cottontale provide the gospel-flavored, slightly juked backing track, and OJ Hays directs.