Upgrades allow players to enhance functionality of the map. They can be used to optimize existing systems, unlock new mechanics, or customize the game world.
Getting/unlocking upgrades depends on the specific gamemode you are currently playing.
Some gamemodes have ways to get upgrades, some are always on a specific upgrade level for certain upgradable things.
For example, in Conquest there are upgrade missions. Completing those missions will unlock an upgrade.
In Rush, there is no way to upgrade the castle. The castle there is in a "fixed state", depending on the zone the gamemode is currently in.
The upgrades on the default map are the following:
/cc2 map value upgrades [upgrade id] [level|(null)]
Upgrades (CastleUpgrade) are managed by the CastleUpgradeManager).
The UpgradeAppliedEvent is fired when an upgrade has been changed. It contanis the previous and the new upgrade level and the upgrade id.
The CastleUpgrade contains a list of Level interfaces (which are representing upgrade levels).
The Level interface contains an onApply and onRemove method.
When an upgrade level has been changed, the onRemove-method of the old upgrade level is called. Then, the onApply-method of the new upgrade level is called.
If the upgrade is removed (unlikely, but possible), only the onRemove-method of the previous applied level is called, without calling any onApply method.
In the implementation of the onRemove method, the entire status of the Level must be completely reversed. After onRemove has been called, none of the changes to the level may remain.
It is absolutely essential that a level is completely cleaned up in the onRemove method. No remnants of the old state may remain. If there are overlaps between the old and new level, these must be explicitly restored in onApply of the new level. IF YOU DON'T FOLLOW THIS RULE, THINGS MAY BREAK!
When the onRemove-method of the battery upgrade is called, it completely removes the battery block structure, regardless if it is there or not. Then, in the onApply-method, it puts the new block structure into the world.
This ensures, that if the battery upgrade is not upgraded linear, but set to a random level, everything is set correctly. This also ensures that if the battery upgrade is removed, all batteries disappear.