Super Mario Galaxy 2/Twisty Trials Galaxy

Star 1: Spinning and Spinning and Spinning
This level can be easy regarding the fact that there are zero enemies, or hard if you can't control yourself on the spinning platforms. There is a Cloud Flower near the beginning. This gives you a little bit of insurance in case you fall, and you fall slower. For a slightly harder challenge, finish the game without using it.

Star 2 (Prankster Comet): Turning Turning Double Time
The blocks turn faster in this level, four extremely fast blocks are added at the end, and the Cloud Flower is gone. Luckily, in the crystal at the flag, Yoshi can be found, and there are a LOT of 1-ups. Again, for a harder challenge, don't use Yoshi.