Level 3999

Level 3999 is the 4000th level of the Backrooms and the final level of Cluster IV. This level serves as one of the few exits from the Backrooms back into reality, also known as the Frontrooms, and it is well-known for that reason.

Description
Level 3999 is a seemingly infinite arcade. The appearance and layout resembling most arcades present in the Frontrooms (eating areas, arcade areas, etc.) However, the arcade machines contain games that require high-performance PCs or Nintendo devices to play, including Call Of Duty, Minecraft, Miitopia, Terraria, Mario Kart 8, Fortnite, Roblox, Among Us, Grand Theft Auto V, and World of Warcraft, among others. Like a typical arcade, the outside area represents a parking lot-cars, streetlights, and trees can be seen through the windows; however, the windows' strength makes it impossible to enter that area.

The arcade machines are durable and enact relaxing effects on wanderers who play on them. To play a game, simply insert a coin. Surprisingly, the machines can take any currency. As wanderers become invested in the game, any sanity loss is mitigated and the wanderer should feel normal within a few minutes. However, attempting to damage the machine, whether in a fit of rage or out of curiosity, will instantly cause the wanderer to faint on the spot. There is luckily no lasting brain damage; regardless, it is not recommended hitting, punching, or swinging at the machines.

Level 3999 is one of the most famous levels due to the familiar feeling of security, safety, and comfort. At the same time, the scarcity of other humans in this level may provoke feelings of anxiety and loneliness.

Occasionally, meteorites may rain down from the ceiling, with no known pattern. However, they do not appear to damage the level or any wanderers, so researchers have hypothesized that they are simply illusions created by the light structures.

Café Studio 52-1

 * The Cafe Studio has an outpost in this level which is a big dining room with infinite food. Almond water, neon water, and more.
 * They have music to chill with and also has a giant pool with relaxing water.

The "Waiters"

 * The Waiters have a colony which trains you to how the arcade games work.
 * If you request them to join their colony, they will say "You need to get our job first."
 * If you ask them for food and water, they will give you the things you asked for.

Frontrooms Organization

 * This, as the name, isn't as a colony or outpost but most likely to be an organization.
 * If you give permission to join them, they will say yes.
 * They also lead helpless travelers to the glass doors.

Entrances

 * Run TRUEEND.EXE in The End's computer to go to this level. This file is not found in every computer, remember that.
 * Heading through an extremely rare glitched purplish wall in Level 11 leads to this level. The odds are extreme, if you find one, congratulations!
 * Heading through an orange wall in any forest-based level leads to this level. You have to be quick because it will disappear after a minute if you don't get through it in time.
 * Heading through a neon blue wall in Level 153 leads to this level.
 * Entering a rare flight with the name of "True End" in Level ∞ leads to this level.
 * Playing an extremely, and I mean, very very very very rare arcade with purple, blue, and black shades will send you here in Level 40.
 * There is a high chance exiting Level 3998 teleports you into this level.

Exits

 * Walk through the glass doors to be sent back to reality.
 * If you faint in Level 3999, there's a rare chance that you will be sent to Level 109.
 * Playing Mario Kart for 30 minutes will lead to Level 69.
 * Playing Minecraft or Roblox for more than 30-60 minutes will lead to a random Quantum Stable Level, most commonly on Level 3.
 * Playing Among Us for 30 minutes will send you to Level Sus.
 * Playing Hearts of Iron IV for 60 minutes will send you to Level 49.
 * No-clipping on a puddle will send you to Level 4000.
 * Finding windows and jumping into those will send you to Level 63.