Super Mario Galaxy 2/Boulder Bowl Galaxy

Boulder Bowl Galaxy is...

Star 1: Rock and Rollodillo
Grab the Rock Mario power-up and head over toward the 6 creatures that look like bowling pins. Knock them all down, then proceed toward the ramp with a double-chevron on it. Roll towards the ramp and you'll be launched to another planet.

After defeating each of the rock-spitting creatures, a launch star will open, sending you toward a planet with Chain Chomps and Lodestones. Transform into Rock Mario again and roll towards the purple crystal containing a jump star.

Now on the golden translucent planet, tag the Mid-point Flag and power-up with the Luma Shop before using the launch star to continue your journey.

Mini Boss: Rollodillo
On the wire mesh planet, you'll be faced with a Rollodillo.

Transform into Rock Mario and roll into the Rollodillo's exposed tail four times to defeat it. Avoid the spines and nose, as you'll not only lose your rock powerup, but also a life wedge with each collision.

Grab the Power Star and return to Spaceship Mario.