Right on the line. Then again. And again.
A perfect drop snaps on with a ring of light and a note, and doubles the slab's points. The next perfect doubles them again: ×2, ×4, ×8, all the way to ×32, the badge wobbling harder the longer it lasts.
Miss the line and the slab is cut, and the slide gets a notch quicker. Land a perfect and it calms a notch again, so you can always win your rhythm back.