You start off in a little platform overlooking a large strip of land blocked off by a moving caterpillar tread. Walk forward onto the tread and stay on it. It will take you to a platform with a crate holding a Crust Bucket Ticket and a ride rail. The ride rail takes you back to where you started. Cross the tread and splat the Octotrooper and Octodivers. Move forward, break the boxes, get the Key (you're now at checkpoint 1), and splat the Twintacle Octotroopers and Octocommanders. Open the Vault and take the Launchpad to your destination. Now you are at checkpoint 2 and in a section with a bunch of weird moving platforms. Break the boxes and use the Ink Storm. Now cross the moving platforms and get to checkpoint 3. Splat the Octocopters, move forward, splat the Octotroopers, ink the Splat-Switchs, and splat all of the Octotroopers and the lone Octocommander. Go to the launchpad and then you'll be at checkpoint 4 in an area with a moving floor and 2 Octocopters. Splat the Octocopters, move across the area, swim up the wall, avoid the Ink Piston, splat the Deluxe Twintacle Octotrooper, and you are at checkpoint 5. Avoid the Octocommanders, swim up the giant moving wall, go down to the side and get the Sardinium, then come back up and you are at checkpoint 6. Use the Ink Switch to move the platform around. At the final checkpoint, the platform will tip, so be aware of that. Hit the splat switch, get the sunken scroll, and get the Zapfish.
Collectibles
Sunken Scroll
“
My dearest Callie and Marie -(STOP)- On a research trip to the cape with Agt 3 -(STOP)- May be late, but left dinner in the fridge -(STOP)-
Location: The platform with the Zapfish on it will have a splat-switch. Inking it will reveal a launchpad to what Sheldon calls a "Deserted Island". Get away from the Octostamp DX to get the scroll, and the launchpad will take you back to the Zapfish.
Sardinium
Location:
After Checkpoint 5, climb over the giant moving wall. Look to your left and look down. There will be a small grassy platform with the Sardinium.
Armor
Platform Madhouse has 3 pieces of armor to collect.