Instructions
Select "Create Mode" from the main menu to enter the level creator.
Press the "square" button on your controller and select the "Goodies" bag. Choose any material you wish from the "Materials" menu and place it on the thick layer. Select the object with the "x" button on your controller and transform it into a rectangle with the right analog stick.
Select a sensor switch from the "Objects" menu of the "Goodies" bag. Place your new switch in the middle of your rectangle.
Add a piston from the "Objects" menu in the "Goodies" bag beneath the rectangle and attach it to the sensor switch. Make sure the time on the piston is set to "0.1" to make it fire immediately. You can tweak the "Max Length" and "Strength" variables to adjust how far the platform bounces your character.