Key LockProgression

A specific named item in inventory unlocks a specific named obstacle in a one-to-one correspondence; item is consumed.

A keyed lock is one-to-one: the red key is rejected by the blue door and opens only the matching red door — specific, not a master key.

How key lock works in Godot

A one-to-one consumable gate: a named item opens a named obstacle, and using it destroys the item. It's flag gating tied to inventory.

The lock checks inventory for the matching key by id. Ownership is the gate; nothing about the door is hardcoded except the id it wants.

func try_open(door):
    if not inventory.has(door.key_id): return false

On success, consume the key and set the door's open flag — the same set_flag pattern as any other progression gate.

    inventory.erase(door.key_id)
    flags[door.id + "_open"] = true
    return true

The physical door. When its open flag is set, disable the collider (or play the open animation) so the path becomes passable.

func _on_flag(name, val):
    if name == id + "_open": $Block.set_deferred("disabled", true)

In short: Interaction checks has_item('iron_key'); on success: remove_item('iron_key') and set_flag('door_open', true)

37 catalogued game(s) use this mechanic, spanning 1986–1997.