World 3-1 (Super Mario Bros.: The Lost Levels)
World 3-1 is the first level of World 3 in Super Mario Bros.: The Lost Levels. In the original release and Super Mario Bros. Deluxe, the level has a standard grassland palette, though Super Mario All-Stars has the level covered in snow. This is the first level in the game with backwards Warp Zones.
The level starts with the player facing two Hammer Bros on two rows of Brick Blocks, one of which on the bottom row contains a Super Star. Across the gap in the right-most block of the first row of ? Blocks is a Poison Mushroom, and the left-most ? Block of the top row contains a power-up. Through the Warp Pipe ahead is an underground area with Coins and a Bill Blaster, which will lead out to a backwards Warp Zone that leads to World 1-1, though there is also a gap the player can chose to jump into to lose a life, thus avoiding the pipe and starting this level over. To the right of the next pipe above ground is a Hidden Block with a power-up, and above the pipe is a Beanstalk that leads to Coin Heaven. After some Koopa Paratroopas and between a few Bill Blasters is a row of ? Blocks, with the left-most one containing a power-up. Directly above the Koopa Paratroopa ahead is a Hidden Block with a 1-Up Mushroom. Through the second Warp Pipe afterward is another underground area that will exit to the pipe underneath the Beanstalk from earlier. After the four pipes is a Super Spring the player can use to jump over the Goal Pole ahead, which will lead to the same backwards Warp Zone from earlier.