Global Control Level

To expand your empire in the game world, you need to develop your main game indicator – your Global Control Level (GCL). It affects two important factors:

Your current Global Control Level is displayed at your overview page.

https://docs.screeps.com/img/gcl-cpu.png

Room Controller Level

In order to build any facilities in a room, you need to control it. In the majority of rooms (but not all), there are special objects called Room Controllers. In your first room, the Controller is owned by you by default. Any neutral Controller can be claimed by your creeps with the CLAIM body part, which instantly puts the room under your control.

https://docs.screeps.com/img/c1.png

A newly-seized Controller allows you to build one spawn in the room. In order for you to build extra spawns, roads, and extensions, you have to upgrade the Room Controller Level (RCL) by pumping energy into the controller using Creep.upgradeController method.

https://docs.screeps.com/img/c2.png

Available structures per RCL

RCL Energy to upgrade Structures
0 Roads, 5 Containers
1 200 Roads, 5 Containers, 1 Spawn
2 45,000 Roads, 5 Containers, 1 Spawn, 5 Extensions (50 capacity), Ramparts (300K max hits), Walls
3 135,000 Roads, 5 Containers, 1 Spawn, 10 Extensions (50 capacity), Ramparts (1M max hits), Walls, 1 Tower
4 405,000 Roads, 5 Containers, 1 Spawn, 20 Extensions (50 capacity), Ramparts (3M max hits), Walls, 1 Tower, Storage
5 1,215,000 Roads, 5 Containers, 1 Spawn, 30 Extensions (50 capacity), Ramparts (10M max hits), Walls, 2 Towers, Storage, 2 Links
6 3,645,000 Roads, 5 Containers, 1 Spawn, 40 Extensions (50 capacity), Ramparts (30M max hits), Walls, 2 Towers, Storage, 3 Links, Extractor, 3 Labs, Terminal
7 10,935,000 Roads, 5 Containers, 2 Spawns, 50 Extensions (100 capacity), Ramparts (100M max hits), Walls, 3 Towers, Storage, 4 Links, Extractor, 6 Labs, Terminal, Factory
8 Roads, 5 Containers, 3 Spawns, 60 Extensions (200 capacity), Ramparts (300M max hits), Walls, 6 Towers, Storage, 6 Links, Extractor, 10 Labs, Terminal, Factory, Observer, Power Spawn, Nuker

Attacking controllers

A Controller cannot be damaged or destroyed. However, a Controller not affected by an upgradeController action will run a downgrade timer losing 20,000 game ticks at RCL 1, or 5,000 game ticks at RCL 2 to 150,000 game ticks at RCL 8. All timers are listed in the StructureController prototype. As soon as its level reaches 0, a Controller becomes neutral, and another player can reclaim it. Make sure that you upgrade your Controllers from time to time to keep their levels!

You can attack another player's controller downgrade timer by applying attackController on it.

https://docs.screeps.com/img/controllerDowngrade.png

Raising GCL

Upgrading GCL requires pumping energy into your Controllers – GCL grows in parallel with the level of your Controllers. Any contribution to any of your Controllers affects your GCL, even if the Controller is fully upgraded to the level 8.

Having upgraded your GCL once, you will never lose it. Even after complete fail in the game and loss of all your rooms, your GCL is stored in your account forever. It allows you to respawn at a new place and quickly regain your former glory.