User:McClaw/Back Wall
From The Blockheads Wiki
The backwall is an interactive portion of a world in The Blockheads.
Although nominally a two-dimensional world, there are three "layers" of depth in The Blockheads: foreground, midground, backwall, and sky.
The backwall sits between the midground (where crafting surfaces set) and the sky. It is filled when a block is in the foreground, a solid block is placed no more than ten blocks above another solid block, or bedrock is exposed.
With the exception of bedrock, if no solid block is above a backwall, the backwall will disappear and be replaced with air.
As of version 1.6, backwalls can be removed individually. Even bedrock backwalls can be removed using a pickaxe.
Backwalls allow the placement of crafting surfaces, stairs, and blocks.