From the Super Mario Wiki
Rolling Snowballs is an official course in Course World in Super Mario Maker 2. It is the first level of Ninji Speedruns, uploaded on December 4, 2019. It is available until December 11, 2019. It is set in the snow theme in the New Super Mario Bros. U style. This level introduces Spikes and Snow Pokeys, who were added in a content update on the same day as the level's release.
The level starts out with a ? Block which contains a Super Mushroom. Next is a Spike on a hill. Mario is then able to take the top route or the bottom route. More Spikes appear, along with Snow Pokeys. There are also snowballs Mario can throw at Spikes and Snow Pokeys to defeat them. There are also larger snowballs Mario is not able to pick up, but he is able to roll them down slopes to defeat certain enemies. After another ? Block with a Super Mushroom inside are a few regular Spikes, two flying Spikes, and one Big Spike. There is another ? Block with another Super Mushroom inside afterward, followed by a large snowball Mario can roll up a slope to defeat a row of Snow Pokeys. There is then a blue pipe giving out large snowballs, one of which Mario can roll down the slope to knock off segments of a particularly tall Snow Pokey, with the Goal Pole right behind him.
"Make your way through the snowfields, and keep an eye out for Spikes and Snow Pokeys! Stomping on Snow Pokeys will turn them into small snowballs, which you can pick up and throw. Play this course as many times as you want, and see if you can find the fastest way to the finish!"
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