The map repeats the world sideways, and zoomed out several copies are on screen
at once. The rings span −180…+180 once, so the shading ended in a hard vertical
edge wherever the next copy began: it read as a rectangle laid over the planet
rather than as night.
Each ring is now drawn again shifted a full turn either way. Three copies cover
every zoom this map reaches and cost nothing — three more polygons on a canvas
layer.
Zooming the map to fit one world would have hidden it rather than fixed it, and
would have taken away the free pan and zoom the operator has.
rouggy
f82631690a