Hey! Here’s an update on the Catapult. It’s a straightforward design. To add the needed stability I simply stacked two 2 x 16 LEGO Plates (4282). To get the balance right was a trial an error thing. The biggest challenge was to prevent the ball from missing the platform side ways (left or right). I didn’t expect that thing to be an issue in the first place. In the end I use two 2 x 4 LEGO Tiles (71150 / 87079) to stabilize the movement.