Dirt Slab - pandorical

Rebuilt for Minecraft 26.3.

• Mixed Slabs integration: terrain slabs built into a mixed slab keep their surface, and a hoe or shovel works that surface and leaves the half underneath alone.
• Sugar cane and bamboo standing on a slab grow as the slab kind all the way up.
• Ops switch terrain slabs in new land on and off from Dirt Slab's page of the Pandorical mods menu, as well as in config/dirt-slab.json. It takes effect from the next restart.