Our first GBC module. Dad found this instructions of a classic marble pump from Brian Alano in Internet. When dad was building, I wanted to help. I insisted, so dad finally gave me a new Star Wars set from his stock to distract me. Of course, it worked.
Update 27th August 2019:
To run in an exposition, the module must be reliable. There were still some very old bricks from the 60th which caused high friction. Additionally we added a liftarm for stability reasons. So it participated in the circuit of CatBrick 2019.
Now we improved the visibility of the mechanism exchanging the window by a panel and putting two panels more.