World 1-1 is the first level of World 1 in Super Mario Bros.: The Lost Levels and is the first level in general of the game. The first screen of the level is also the game's title screen when starting it up.
The player starts on a path with a Koopa Paratroopa jumping towards them. Up ahead is a square-shaped formation of blocks, with the second-from-the-left Brick Block containing a Super Mushroom; to collect the power-up, the player needs to bump a block from below with the proper timing to make the Super Mushroom bounce over a ledge. In the middle block of the row of ? Blocks ahead is a Poison Mushroom. Past the second pipe and above the tree in the background is a Hidden Blockwith a 1-Up Mushroom. Across the gap and in the left-most Brick Block of the bottom row is a Super Star, and the block to the right of the stone stairs ahead is a Coin Block. Using the upper Brick Blocks to cross a chasm, the player will come across a row of Koopa Troopas and some ? Blocks, the third-from-the-left of which contains a Poison Mushroom. After a row of enemies are two pipes, with the second one leading to an underground area containing some coins and Hidden Blocks containing a Poison Mushroom or a power-up. In the right-most ? Block under the floating pipe ahead is a power-up. Across the chasm and the pipe the player exits out of the underground area is a flight of stairs leading to the Goal Pole.