Metal Gear is a Japanese franchise of action-adventure stealth games created by Hideo Kojima. Developed and published by Konami, the first game, Metal Gear, was released in 1987 for MSX home computers. (via Wikipedia)
The genre Metal Gear helped define
Stealth. avoidance over combat, with guard detection as the central challenge.
The game mechanics of Metal Gear
Free 2D MovementTraversalPlayer moves freely in 2D space with no forced scroll; camera follows player position.
Boss EncounterCombatA single high-health enemy with unique scripted behavior and distinct phases serves as a gated progress challenge.
Real Time Action CombatCombatCombat resolves continuously in real time; player inputs compete directly with enemy behavior each frame.
Stealth DetectionCombatEnemies have multi-state awareness of the player; avoidance rather than engagement is the primary success condition.
Inventory ManagementResourcePlayer holds a collection of discrete named items with defined slot limits; deciding what to carry is a meaningful choice.
Flag GatingProgressionA boolean or enum stored in global state determines whether an event, path, or interaction is currently available.
Key LockProgressionA specific named item in inventory unlocks a specific named obstacle in a one-to-one correspondence; item is consumed.
Detection State MachineSimulationEnemies cycle through named awareness states (unaware / suspicious / alert / searching) based on sensory input from the player.
Each mechanic links to how to build it in Godot, with the retro games that share it.