About 4 and a half years ago, Sethbling released DeathSwap, one of the first games created by command blocks. Recently, a friend and I remastered it and made it better. It all fits inside of a 6x6x6 Cube, and is very lightweight on servers.

How to Install: Client & Server

If you are installing for a server, follow all the client instructions before starting the server instructions

Create a world that you would like to use as the death swap world, make sure Cheats are ON
Exit fully out of minecraft.

Locate your saves folder, usually under:

%appdata% > Roaming > .minecraft > saves

and choose the folder named the same thing as you named the death swap world.

If not already existing, create a "structures" folder

Unzip the DeathSwap file, and drag the deathswap.nbt into the structures folder.

Load back into minecraft.

Open up the world, and right when you get in-game, type the following command:

/give @s structure_block

You should acquire a purplish block.

Place down this block, and set it's mode to 'Load'

in the 'Structure Name' box, type in deathswap, then hit "LOAD"

It should create an outline of a box, which then you can open it and hit "LOAD" again

This should load the 6x6x6 structure into the world.

Client/Lan: Open up the world to LAN, and when ready, hit the Start Game button

Server Instructions: Make sure the server is stopped when you are doing this.
Once the box is loaded in, Save and Quit the game.

Open up your server folder, and delete or rename the current 'world' file to something else.

Drag the death swap world file into the server folder, then rename it to world

Open up the server.properties file, and make sure that command blocks are enabled,

Start up your server and enjoy!