The 2.5D waterline

Icecap Zone 2 also has a pseudo-3D effect going on in its background waterline. There's no vertical scrolling this time around, but on the other hand, the ice sheets floating on the water's surface display some realistic perspective as they scroll horizontally across the screen.

Once again, the parallax effect is achieved by scrolling each row of pixels faster than the one preceding it, but this time there's no DMA trickery involved. Turns out, the background itself was drawn skewed in advance, so by the time one of the four sets of ice sheets scrolls offscreen, the remaining three have deformed exactly the right amount in order for the animation to loop seamlessly.