World 3-4

Hop onto the large ice block at Point 1 and ride it across the small gaps. Don’t try to Gap-Dash across them; you’ll only hit the sliding block and get pushed to your death.

Carefully jump across the sliding blocks while avoiding the Red Koopas between them. When you reach the other side, hit the Roulette Block and collect your power-up.

Beating World 3-5 gives you access to the large ! Switch on the World 3 overview map (on the far right). After you hit the ! Switch, all the Invisible Blocks in World 3-4 and World 3-5 become solid red blocks.

So, to be clear, this is only accessible on the second play-through, after you hit the ! Switch, not the first time you play this level. This allows you to slide across the red blocks to the pipe at Point 5 to access a secret cavern with several coins.

Grab one of the ice blocks on the left and hurl it at the Goombas on the right. Dash behind the block as it goes and grab all the coins that appear!

Grab the POW Block at Point 7 and carry it onto the large, sliding block on the right. As you ride the block across the chasm, drop the POW Block to force all the coins above you to drop!