World 1-1 is the first level of Grass Land in Super Mario Bros. 3 and its remakes Super Mario All-Stars and Super Mario Advance 4: Super Mario Bros. 3. The player is given a time limit of 300 seconds to complete it.
This is a nature-themed level that features several bushes, platforms, coins, and ? Blocks. The player will encounter common enemies such as Goomba, Piranha Plants, Koopa Troopas, and more. This level introduces the Super Leaf power-up, which allows Mario or Luigi to transform into their raccoon counterparts.
The player begins near some ? Blocks and a single Goomba approaching them. Further up is a pipe containing a Venus Fire Trap, or a normal Piranha Plant in the GBA remake. Ahead are several platforms where some Koopa Troopas and some more Goombas are found. Ahead is a ? Block containing a power-up. If the player is already in super form, the item will emerge as a Super Leaf. With it, the player, after defeating the Goombas in their path, can get a running start and fly up towards a secret cloud area, where they can collect coins and be lead to a pipe leading to another area, where they can gather more coins, which is placed to form the number 3, most likely serving as a reference to the game.
On the regular path, below the cloud area, are some more platforms featuring a few Koopa Paratroopas. Ahead is an area where the player can activate a P-Switch to temporarily turn a stack of Brick Blocks into coins. Just up ahead is the pipe (which leads out of the secret area), followed by the darkness up ahead, where the goal is.