In the original "Super Mario Bros." for the NES released in 1985, Mario and Luigi do not have any gameplay differences. Both characters control identically in terms of running speed, jumping height, and general mechanics. The choice between Mario and Luigi is purely cosmetic, allowing a second player to distinguish themselves from the first player during a two-player game. It wasn't until later games, such as "Super Mario Bros. 2" and others in the franchise, that the characters began to exhibit unique abilities and characteristics. Here are the key points for clarity and future reference: - In the original "Super Mario Bros." (1985), Mario and Luigi are functionally identical in how they play. - They have the same running speed, jump height, and reaction to power-ups. - The choice of character doesn’t affect the game’s difficulty, level design, or enemy behavior. - Their unique visual designs serve to differentiate Player 1 (Mario) from Player 2 (Luigi) in the game's two-player mode. - Variations in character abilities came into play in subsequent games, with "Super Mario Bros. 2" introducing different jump heights and strengths among the characters for the first time. Understanding this information is useful not just from a historical gaming perspective, but also for those interested in game design and the evolution of character differentiation in video games.