How to Find the World 4 Cannon on Super Mario Bros?

Progress in the game to the World 4 Ghost House. Before entering, make sure that you have a mini-mush. Select the level to enter.

Run through the house. On the lower level of platforms you will see a door. Enter it.

Jump onto the yellow "?" block. More yellow "?" blocks will come down from the ceiling. Jump on top of the second block from the left. The blocks will return upwards, taking you through a portal.

Run to the far right side of the level you are on. You will see a platform near the end that you must jump on in order to pass a wall. Jump past Big Boo up to the next level of platforms. Jump on the red button to the left to solidify the block outlines. Red blocks will appear under a door. Go through the door.

Run all the way to the left and jump on another red button. Run back to the right. You will see two vertical lines of red blocks. Jump up to hit one of them and jump again as you hit. This will bounce you off the wall and into the other. Continue to do this until you go through the gray blocks onto the next level.

Jump up and hit the silver star coin. Once you have done this, wait for the red block button to wear off and run to the left. You will fall down to the level you were on before. Hit the red button again. Run to the right and jump onto the platform at the far right. Use the red blocks to get up onto the pipe to the left of the platform.

Use the mini-mush. Jump up and against the pipe. Bounce off the pipe and toward the right, landing on a platform against the right wall. Use the method of bouncing between walls to get up between the steel walls to the higher level, where you will see a door. Do not go through it.

Bounce between the walls again up to the very top of the screen, where you will collect a gold star coin. Let yourself fall back down and go through the door.

Run to the right where there will be a platform before a flag pole. Jump onto the flag as high on the pole as you can. This will take you out of the level. When you return to the map, a path to the cannon will appear. Follow it and the cannon will shoot you to World 7.