World 1-4 (Super Mario Bros.)

World 1-4 is the final course of World 1 in Super Mario Bros.. It is a castle course and the Bowser Impostor found in the level is actually a Goomba.

Layout
Mario starts the level on an elevated area with stairs heading downwards. There is a gap with lava and, right after it, a block. There are also two lava gaps with a Fire Bar on the platform between them. It contains a Question Block with a Fire Flower in it. Past it, a corridor with three Fire Bars must be crossed. Mario reaches a room with three Fire Bars, two on the floor and one on the roof, along two blocks. He, then, finds another room with six hidden blocks. In this area, the Bowser Impostor's fireballs start to appear. Mario can use a gap to avoid these fireballs and then, the Bowser Impostor is seen on a bridge with a small platform moving from side to side right above him. If Mario gets past the Bowser Impostor by either using the platform or running under him and touches the axe, the bridge collapses, causing him to fall into the lava. A mushroom retainer is saved and Mario gains access to World 2.

Trivia

 * The level and the boss fight has been re-created in New Super Mario Bros. 2, in Gold Classics Pack from Coin Rush on the final course along with World 1-1 from said game.
 * It was also released in Japan on the e-Reader.