New Super Mario Bros. U: Frosted Glacier-4 -- Scaling the Mountainside

This level features flying squirrels and Bullet Bills, so you'll have to be careful with all the enemies flying around. Wall jump up around the set of low coins for brick blocks with a power-up. The first Star Coin is over one of the balances. The Acorn Mushroom is in this level, so use it to boost to the Star Coin. The second Star Coin is over the set of four Bill Blasters. Glide and boost to get it. Soon after is the midpoint. There is an item block high above some brick blocks. One of the brick blocks has a spring. Move the spring to the right wall to get a 1-up in an invisible block. Next, is a set of Red Coins, which go over a couple of balances with skinny platforms. Over the left Bill Blaster is a hidden area with the third Star Coin. Glide and boost from the ledge to the right to reach it. There's a set of balances and a Banzai Bill before the flagpole. This opens the path to the Ghost House.