Ride the Switchboard and dodge the cannons and Parabones until you reach a platform with a ? Block . Pop it to collect a Cannon Box that you need. As you move around the loop fire a charged cannonball into the ? Blocks across the way to extend a platform to the Stamp then quickly return so you can reach the main area.
There are more Cannon Boxes here if you need them so hop up and blow everything away. Next, you must scale the wall by bouncing from cannonball to cannonball. Time your jump and hold down the jump button to easily bounce off of the cannonball and on to the next until you reach the top. At the right is a cracked wall, blow it up for Green Star #1 , the other side has some coins.
Continue to the pipe where you wind up underwater. Collect another Cannon Box if you need and take the clear pipe. Stay along the bottom as the platform rises, breaking the blocks to enter the center here where Green Star #2 can be collected.
If you’re fast enough, swim up and into the clear pipe, holding down to snag a Green +Clock before exiting the water. After all that you are rewarded with the Checkpoint Flag . Take a Cannon Box and ride the Switchboard out, firing at the ! Block to extend the platform. After the first extension, shoot another ! Block to move north. Fire a cannonball at Green Star #3 , it’s impossible to reach it without riding the Switchboard to your doom so just shoot it quickly the change direction. Revert the path once you are safely back on the track then continue right.