Following the open, outdoor setting of World 1-1, World 1-2 immerses the player in a dark, underground cave (or sewer). The level's design builds upon the skills taught in the first level, but in a more confined space.[2] The ceiling forces players to be more precise with their jumps to avoid hitting their head and falling into enemies or pits. The level is populated with Goombas, Koopas and Piranha Plants, which emerge from the iconic green pipes, teaching players to be aware of environmental hazards.[3]
A key element of World 1-2 is its emphasis on secrets. Players are encouraged to break bricks, a mechanic learned in World 1-1, which can reveal hidden power-ups like a 1-Up Mushroom.
World 1-2 is most famous for containing the game's first Warp Zone. Near the end of the level, there are two rising platforms. By riding the second platform to the top of the screen, the player can jump onto the ceiling and walk over the normal exit pipe. This leads to a secret room with pipes that allow the player to "warp" directly to World 2, 3, or 4. This feature was a significant factor in the game's popularity, encouraging exploration and adding immense replay value.[4] The discovery of this secret became a legendary part of gaming culture in the 1980s.[5] If the player exploits a glitch, which maneuvers Mario through the bricks next to the Warp Zone and enters World 4, instead of entering World 4, the player ends up in the Minus World.
As the first underground level and the introduction to secret warp zones, World 1-2 is a pivotal stage in Super Mario Bros. It established design tropes that would become staples of the platforming genre. The level's design philosophy, which teaches mechanics through interaction rather than explicit instruction, is considered a masterclass in game design.[6]
