Introducing "Captive Minecraft," a Survival gametype that uses achievements and the world border to great effect. You start on a 1x1 box, and every achievement you get widens the world border by half a block in all directions.

"As your captive world slowly expands, you gain access to more and more resources," a post on the gametype's website says. "You'll have no trouble Getting Wood or Taking Inventory, but suddenly making that Cake and riding a Pig off a cliff isn't quite so simple..."

You can download Captive Minecraft here—note that the creators highly suggest you play this with friends. This is what you need to get it up and running:

You need to be running Minecraft 1.8 snapshot 14w18b or later. You can set this up right in the Minecraft Launcher. Edit your profile to include experimental "snapshots" and choose the 'Latest Version'.

Now download the world save, place it in your /minecraft/saves folder and unzip it. You'll be able to access it from your single player menu now.

If you're going to run a server, you MUST have Command blocks enabled in server.properties!

And in case you wanted some tips on how to play this, from the gametype's website:

    • You can hold TAB to see who of your friends has earned the most Achievements.
    • There seems to be a bug at the moment where Chickens will die immediately if they touch the World Border if it's set to an even number. Make sure to lock them up as soon as they spawn!
    • Entering the Nether is intermittently successful. Don't take anything valuable, and try relogging if you're dying immediately. It's best to widen the World Border as much as possible before going through your portal... the space in there is 8 times smaller than in the Overworld.
    • Due to obvious limitations, the "On a Rail" Achievement cannot be completed.
    • At this point, when you visit the End, you won't be able to move, as you are technically outside the World Border. Strangely, you don't seem to suffocate. This may change!
    • Every now and then, you'll get some new "friends" join you in your world. Best not to cover up that first Quartz Block.
    • The Sniper Duel Achievement is possible! But you need to have a fair few Achievements under your belt before you can access the appropriate area...