A guide to completing World 1-2 in Super Mario Bros 3 for the Nintendo Entertainment System.
How to Clear World 1-2
Go to the right and you find a pipe. You can't walk into it, so just jump on top of it. Before you jump off the right side, beware of the Goombas that pop out of the right side of the pipe. If you stand on the slope to the right of the pipe, you can press DOWN to slide down the slope, and if you're sliding quickly enough, you'll defeat any Goombas in your way. But if you slow down too much, the Goombas will hurt you instead, so beware.
After the slope, there is a ? block that contains a Super Mushroom or Super Leaf.
Jump onto that block, then jump on top of the sideways pipe, and go to the right. As soon as you jump down from the right side of the pipe, Goombas will start coming out of the right side of the pipe, so try not to let them hit you.
There is a Para-Goomba to the right of that, then a slope leading up to a pipe. Keep going to the right, and stand on the pipe at the top of the hill. If you DON'T collect the coins on the right, you can turn them into bricks using a hidden P Switch nearby, allowing you to reach a pipe with a hidden 1UP Mushroom above it, and a hidden area if you go down that pipe. This can be a bit difficult, so it might take multiple tries. If you're not interested, skip the next paragraph.
Carefully slide down the hill without collecting any of the coins, then as soon as you're at the bottom of the slope, start pushing RIGHT on the directional pad and you will run toward the two low blocks. If you're Super Mario or Raccoon Mario, press DOWN and you should crouch and slide beneath the two bricks. Quickly jump to hit the leftmost of the two bricks, to make a P Switch appear. Jump on the switch, then quickly jump up the now-solid bricks on the left to reach the pipe up above. Be careful not to get hit by the Venus Fire Trap's fireballs. Jump onto the pipe, but before you go down it, stand on the rightmost edge of the pipe and jump straight up to make a hidden 1UP Mushroom pop out of a hidden brick above you. Go to the left and jump to try to get that Mushroom before it falls, but try not to fall off. If you didn't fall off, you can go down the pipe to reach a hidden area. You will fall down below and land on a pile of bricks if the P Switch is still in effect. Wait for the P Switch to wear off so the bricks turn back into coins. Collect them, then go through the pipe to exit the hidden area. If you fell off without reaching the hidden area, you have to be Raccoon Mario and make a running start to fly on top of the Venus Fire Trap's pipe to reach the hidden area.
After that, feel free to collect the coins that you used as brick platforms (if you followed the steps in the previous paragraph). Then go to the right and get past the Goomba on the tall hill. Then go to the right and you find a couple of Jump Blocks (they have ♩ on them) and a Para-Goomba. If you jump on top of a Jump Block, you will bounce. If you press the Jump button at the right time, you can use the Jump Block to jump much higher than normal. The second Jump Block contains a Super Mushroom or Super Leaf.
You can slide down the next hill to defeat the two Goombas there. Then there is a pipe with a Venus Fire Trap, and a series of three Jump Blocks. The third one contains a Starman. If you collect it, you become temporarily invincible. Any enemy you hit while invincible will be defeated. But you will still die if you fall in a hole.
Go to the right, past the Goomba and the Venus Fire Trap. The ? block contains one coin. Go past the pipe, slide down the slope, and beware of the Para-Goomba near the dark area at the end of the level. While running at top speed, jump and hit the Goal Block at a 45° angle to try to get a Star (or just hit it when it's showing a different symbol if you're trying to match something else).
After the Level
After you complete the level, you can now choose between three different destinations. If you clear World 1-3 or World 1-4, you can go to the first Toad House, where you can choose a treasure chest for a chance to get a Super Mushroom, a Fire Flower, or a Super Leaf. The item can only be used on the Map Screen. Press B to display your items, use the directional pad to select an item, and press A to use it.
Or you can ignore World 1-3 and World 1-4 and instead go to the Spade House, where you can play a slot machine for a chance to get extra lives. The slot machine is completely random, so don't worry about the timing of your button presses.
Or you can go past the Spade House (you don't have to play the Spade House game to go past it) and enter the World 1 Fortress.