World 1 (Super Mario Bros.: The Lost Levels)

World 1 is the first world found in the Japanese version of Super Mario Bros. 2. The world is well-known for bearing many similarities to the original game's, but the sprites had been advanced and the levels were much harder. This was the first world in any game to introduce the Poison Mushroom.

World 1-1

The player starts out next to the castle on a rocky pathway. As the player moves forward, he will encounter a jumping Koopa Paratroopa. The player must avoid this enemy, and then the player will be standing under a layer of bricks. If the player hits the brick that's second-to-the-left, a mushroom will appear. Then the player must avoid the two piranha plants and jump over a green pipe. Over the tree next to the pipe there is an invisible 1-Up block that the player can get (optional).

After jumping over a hole, the player will come across a swarm of Koopa Troopas. The player avoided these and jumped over another two pipes (one of which contained a piranha plant, and the other lead to a coin room). In the last ? block of the level, the player found a Super Mushroom/Fire Flower (optional).

Lastly, the player reached the Ending Staircase of the level, and the Flagpole afterward.

World 1-2

This is the first underground level of the game. There is a small cutscene at the beginning of the level showing Mario or Luigi (whomever the player is playing as) walking into a pipe in the overworld. The plumber will then plummet into the underground.

In this level, there are goombas, piranha plants, and koopa troopas to avoid, and a large canyon where the player must quickly jump over mushroom floors (which drop if stepped on) to cross. As it is the first underground level of the game, it is also the first time the player can go to a Warp Zone, which leads to World 2-1.