IMPORTANT:

This is an early version!
I want feedback so I can improve and add more levels, so if you have one or found a bug, please comment on this post.

The datapack uses custom dimensions, so if you want to add it to your sever, make sure it's a vanilla server.
To check if it works, type /execute in and see if there are options like gd_br:level_0.

Because this is an early version, you must use commands to noclip to the backrooms:

/function gd_br:tp_backrooms/start_noclip - Noclip yourself to the backrooms.
/execute as <PLAYER NAME> at @s run function gd_br:tp_backrooms/start_noclip - Noclip other players to the backrooms (make sure to change the <PLAYER NAME> to the name of the player you want to teleport).
Note: The 2 commands above only work on players.
/function gd_br:tp_backrooms/tp_level_<NUMBER> - Teleport to specific levels in the backrooms (make sure to change the <NUMBER> to a number between 0 and 6, example: /function gd_br:tp_backrooms/tp_level_4 - will teleport you to level 4 in the backrooms).