1.1 is a release file of the Minecraft map FlatMode - Superflat Challenge, made for Minecraft 1.20, 1.20-Snapshot. It was published on October 12, 2023 and is 0.1 MB in size. For the full description, screenshots and every other version, visit the FlatMode - Superflat Challenge map page.
How to install: Extract the .zip and move the world folder into .minecraft/saves; the map then appears in your Singleplayer list.