Swing out and make a half turn. Swing back to the platform. Sweep back slightly earlier than for a swing so that you rise into your set at the front end early. Then sweep your legs back straight, let go and make a straight front somersault with 1½ twists to catch wrists.
You can find out more about this trick in my books:
Thanks to Kaz, Gordo, Antoly and Dallas for providing videos for this page.