seadragon on the apple II did scrolling, as did a lot of shmup and shmup ports. I've never written a side scroller so I don't know how much of the gravity/plat

seadragon on the apple II did scrolling, as did a lot of shmup and shmup ports. I've never written a side scroller so I don't know how much of the gravity/platform mechanic complicates the scrolling, but I imagine it's about the same thing as shmups with hitboxes, sprites, etc.