Seamless World Wrap

First release.

• Worlds that wrap around: east-west, north-south, or both, from 1 x 1 chunk up to 2048 x 2048.
• Crossing an edge is seamless: the land on the other side is preloaded, and nothing reloads or flickers when you cross.
• Build across the edge; blocks, chests, redstone, minecarts, mobs and arrows all work across it.
• The terrain blends across the edges, so the world looks like it was always one piece.
• World Wrap tab on the Create World screen. Settings are saved per world.
• Existing worlds are never changed. New worlds wrap by default; turn it off on the World Wrap tab. A wrapped world needs the mod to keep looping.
• The Nether wraps at 1/8 scale so portals line up; the End has its own settings (same as the Overworld by default).
• Start in a Forest: the world is centered on forested dry land.
• Small worlds are beatable: an End portal room and a blaze spawner room are added when the world is too small for a stronghold or fortress, and the dragon fight is scaled to fit small Ends.
• With the mod on the client too: copies of you and every mob are drawn across the edges (a hall of mirrors in tiny worlds), and hitboxes stay on the nearest copy.

Known limitations:

• Mobs don't yet chase or pathfind across an edge.
• Light doesn't carry across an edge.
• An axis that doesn't wrap is endless (no wall at the edge yet).
• With Sodium or another renderer replacement, nearby chunks rebuild briefly after crossing.
• Not yet tested: multiplayer with several players, joining with an unmodded client.