A guide to completing World 6-8 in Super Mario Bros 3 for the Nintendo Entertainment System.
How to Clear World 6-8
Pick up an Ice Block (hold the run button while standing next to one) and take it to the ? Block above. Let go of the run button to kick the Ice Block at the ? Block, and get the Super Mushroom or Super Leaf.
There is a Ptooie Plant with a spiked ball above it. Avoid letting it hit you, and go to the right. There is a Green Koopa Troopa, followed by several Walking Piranhas, and three Spikes. You can stomp the Koopa Troopa, then kick its shell into the Walking Piranhas, and run behind the shell so it will hit those enemies.
Then the slope goes down to a Buster Beetle and some Ice Bricks. If you are still following the Koopa Shell, be sure to jump over it when it bounces back in your direction. If you don't still have the shell, you can slide down the slope to defeat the Buster Beetle.
Then, pick up the Ice Bricks and kick one of them at the ? Block to get a Super Mushroom or Super Leaf.
To the right, there are more Ice Bricks, including a set of Ice Bricks that is shaped like the letter H. If you want a 1UP Mushroom, you need to jump onto the upper right column of Ice Bricks in that set. To do so, jump up and remove bricks to the left of the middle platform of the structure, while avoiding or defeating the Buster Beetle in the area. Then jump onto the middle platform when you have removed the Ice Bricks in the way, and jump from there to the top of the rightmost column. Then jump straight up to hit the hidden ? Block and make the 1UP Mushroom appear.
Before you move on, take an Ice Brick, then jump up onto the grassy hill on the right, and kick the Ice Brick through the three Walking Piranhas. Run to the right, and the Ice Brick will hit the Buster Beetle on the slope. Or you can slide down the slope to defeat the Buster Beetle.
Next, there is a wooden platform with some bricks, ice bricks, and Buster Beetles. Hit the upper brick to make a P Switch appear. Then run to the right along the flat area, then fly up to the left to find a lot of coins that appeared with the P Switch. Collect as many as you can.
Afterward, go to the right and hit the Goal Block to complete the level.
After the Level
Next, if you want a shortcut through World 6-9, you can use a P Wing before you enter it. Or, if you have a Frog Suit, you can use it before entering World 6-9 to be able to get some coins and three 1UP Mushrooms.
Proceed to World 6-9 or World 6-10.