World 3 (Super Mario Bros.)

World 3 is the third world of Super Mario Bros. (as most would guess). World 3 is the first world in the game to be set at nighttime. This world also introduces one of the most difficult enemies to defeat: the Hammer Bros. This world consists of to ground levels, one level set at the heights, and one that is a castle.

World 3-1
In the first level of world 3, many of the same obstacles are encountered. Among these are Goombas, Koopas, Piranha Plants, gaps, pipes, and of course many Brick and ? Blocks. A new addition is encountered however: the Hammer Bros. which come in pairs around two flights of Brick Blocks. This increases the difficulty by quite a lot, for the Hammer Bros. are hard to defeat if the player cannot throw fireballs.

World 3-2
World 3-2 is yet another ground level that features the basic obstacles yet again. Gaps are slightly larger in this level though, and more enemies are encountered.

World 3-3
World 3-3 is the first of only two levels that are set at great heights at night. This level features Goombas and Koopas as the only enemies. Due to the lack of enemies, larger gaps are found throughout the level. Moving platforms and suspended platforms are also encountered in this level that require skillful jumping and maneuvering in order to survive.

World 3-4
World 3-4 is a castle level, so it is very difficult. Enemies in this level include firebars, podoboos, and a False Bowser. The player must jump across pits of lava as well as carefully maneuver through spinning firebars that hurt the player if touched. Once the False Bowser is defeated, the player finds that another Mushroom Retainer is in the castle, and not Princess Toadstool, meaning that the player still has a ways to go.

Trivia

 * Though the world is set and night, the clouds are still pure white in color, rather than a grayish color as it would be in real life. Also, the nighttime setting does not effect any colorization or view in the levels.