World 4 (Super Mario Bros.)
World 4 is the fourth world of Super Mario Bros.. This world once again takes place in daylight. This world introduces Lakitus, Spinies, and Buzzy Beetles as main enemies, and is the last to feature an underground level.
 Level Information
 World 4-1
Right after the first Warp Pipe encountered, a Lakitu is found in the sky tossing down Spinies on the player. He is the main obstacle of the level. The player can jump on top of a brick in order to jump on the Lakitu (or throw a fireball at it) and defeat it. Another Lakitu will then appear later on in the level. The player must avoid the typical gaps in this level, however, Piranha Plants, Lakitus, and Spinies are the only enemies encountered in this level. It is possible for the player to do a running jump over the Piranha Plants. The player must traverse the entire level while avoiding falling Spinies, until the final flagpole is reached.
 World 4-2
This is the second and last underground level in the game. This level is more difficult than World 1-2, for it features cramped areas full of Goombas, Koopa Troopas and Piranha Plants, large gaps, high pipes to overcome, and the addition of Buzzy Beetles. This level also features secret warp pipes to World 5, World 6, World 7, and World 8 (the final world).
 World 4-3
 World 4-4
This final level of World 4 is a castle level. It features the typical firebars, podoboos, and another False Bowser, but it also features Piranha Plants and a few sections that are a puzzle; These sections must be walked through in the right patterns in order to move on to the end, making this quite a difficult level. Once the player defeats the False Bowser, the player finds a Mushroom Retainer once more, rather than Princess Toadstool, meaning the player must go on.