What is linear lock?

In game design, a linear lock refers to any lock (object, system or mechanic that restricts player progression) which is opened after a single key is used in a specific way. In comparison to other types of locks, only one key is required (and-locks need more than one key to be opened) and the key is unique (or-locks can be opened with any key of a specific type)

In game design, a linear lock refers to any mechanism that restricts player progression and is opened after a single key is used in a specific way. This mechanism can have many forms, such as a mechanic, an interactable, a lock or even an NPC that makes a request. The linearity of the lock refers to the number and nature of the required keys. In first place, only one key is required, which may be hinted with an image or a text indicating that the player needs something for that lock. Second, linear locks are unique, that is, there is only one key that can open the lock.

Linear locks are the most simple and common locks in games, as they do not overwhelm players with different options due to the uniqueness. In most adventure and platform games, players may find keys and mechanisms that can be unlocked with these keys. Once the player finds the lock, the key generally disappears and the mechanism unlocks. Tomb Raider is filled with linear locks: Lara may find an artifact, a key or a lever that activates a mechanism or opens a door that leads to a new or even secret area. Some games destroy these keys once they are used as they are unique, they may disappear from the inventory or players may be able to dispose of the key if they want to do so.