World 5-A (New Super Mario Bros.)
From the Super Mario Wiki
This level has Mushroom Platforms that shrink and expand. Mario should to time his jumps, because not all platforms move at the same time as each other.. After the checkpoint, Mario can get the first Star Coin by going down to a Mushroom Platform. He needs to hit a ! Switch to return. Just after that, Mario should find a single block. If he hits it by running and jumping, a Beanstalk will pop out, taking him to an area with the second Star Coin. The player should later see two Mushroom Platforms that are able to touch each other. Mario should stand in between them and jump when they shrink, getting the last Star Coin. Then, Mario will reach the Goal Pole.