Minecraft is a terribly addictive (but worthwhile) game where you try to survive in a harsh, unforgiving wilderness made of Lego-like cubes. And once you learn how to survive, then you build the Eiffel tower, or a cool cave fortress, or stuff like that.
Each Minecraft world is driven by a seed — a single number that powers the world-creation algorithm. The world is almost infinitely large. (Much larger than the Earth, in scale). However, the game only creates the parts of the world that you visit. The creation of new world “chunks” always happens just outside your view so you never notice it.
When a new Minecraft update is released, sometimes the world generator is changed. This makes the world seed create a new and different world than it did with the previous version. The player notices this when they enter new terrain and discover jarring discontinuities. Mountains cleaved in half, that sort of thing.
In order to stop this, I created a program that takes the Minecraft world you’ve visited so far and builds a wall around it. The wall creates a psychological and in-game barrier that delineates “old world” from “new world.”
It also poses a challenge to players as the wall is cored with impenetrable material. Players have to build a staircase to get over the wall, or they can tunnel deep below the earth to get under it. The players’ reward for getting around the wall is a new and exciting world.
If you run a multiplayer Minecraft server and are faced with a world-altering version update (such as right now as the game goes from 1.7.3 to 1.8) I would recommend you try buildawall to mark the end of the world and the beginning of the new one.