02 / min-height

html { min-height: 100dvh }. Checkshort first — clean. The tile is now at least viewport height, so the wrap is never on screen.

Then pull past either end in tall. The band is still there, unchanged. Growing the tile moves where the join lands; it does nothing about its two edges being different colours.

That is the trap this page exists for. It fixes the symptom you notice first and looks like the end of it. Hiding a join is not the same as making the edges match, and no amount of height gets you the second one.