The Purdie half-time shuffle — Bernard Purdie's signature groove, the one Jeff Porcaro built Rosanna on and Purdie played on Steely Dan's Home at Last. It is a shuffle at half speed: the snare backbeat moves from 2 and 4 to beat 3 only, so each bar feels like one long, rolling phrase.
How it sits: the hi-hat plays the shuffle on every beat (first and third triplet partials). The snare fills the middle partial of every triplet with ghost notes, so hat and snare together make an unbroken stream of triplets with the backbeat poking out on 3. The kick lands on 1 and on the last partial of beat 2, pushing into the backbeat; the bass doubles it.
Listen for how quiet the ghosts are — felt more than heard — against a fat, late-feeling crack on 3.
Practice: hat and backbeat alone first, then add the ghosts one beat at a time; keep them at a whisper.