the original Super Mario Bros. on the NES does not feature a traditional save system. If you lose all your lives, it's game over, and you'll have to start from the beginning of World 1-1. However, if you get a Game Over, you can hold A and press Start on the title screen to continue from the beginning of the world you were in (e.g., if you got a Game Over in World 4-2, you'd restart at World 4-1). This 'continue' feature is a small mercy, but it still means significant progress can be lost. Modern re-releases or emulators might offer save states, but for the authentic experience, be prepared for a challenging journey without frequent checkpoints.
