01 / control

Nothing applied. background-size: 1000% sets width only, so the height resolves to 100% of the box — one tile vertically, top and bottom edges at opposite ends of a -45deg ramp, repeating.

In short mode those edges meet below html: the seam. Now switch to tall and pull past either end — they meet again in the overscroll region: the band.

One fault, two symptoms, in the two places the canvas paints outside the tile. They look like unrelated bugs, which is how they get fixed separately and wrongly. Use dark mode and the probe; the light gradient is white with 10%-alpha stops and hides both.