Double Dragon is a beat 'em up video game series originally developed and published by Technōs Japan. It began with the release of the arcade game Double Dragon in 1987. The series features twin martial artists, Billy and Jimmy Lee, as they fight against various adversaries and rivals. (via Wikipedia)
Scrolling MovementTraversalWorld scrolls in one or two axes as the player moves or time passes; player exists within an advancing boundary.
Boss EncounterCombatA single high-health enemy with unique scripted behavior and distinct phases serves as a gated progress challenge.
Contact DamageCombatTouching an enemy or environmental hazard deals damage to the player without any explicit attack trigger from either party.
Hit Stun i-framesCombatTaking damage triggers a brief invincibility window during which further hits are ignored; the window length is a tunable design variable.
Real Time Action CombatCombatCombat resolves continuously in real time; player inputs compete directly with enemy behavior each frame.
Weapon SwitchingCombatPlayer carries multiple discrete weapons with different properties; active weapon is selected from inventory.
Lives SystemResourcePlayer has a finite number of attempts; losing all lives resets progress to a defined point or ends the game.
Linear LevelsWorldWorld consists of discrete stages played in a fixed sequence; stages are self-contained with no backtracking between them.
Each mechanic links to how to build it in Godot, with the retro games that share it.