This is an alternate switch for the uhltimate Gauss Cannon design at https://makerworld.com/en/models/205695#profileId-225821

It has 4 benefits:

1. You can see if marbles are in the entrance or exit.
2. You can load the exit marble from the top. It just rolls in place.
3. It is possible to reload the cannon (moving the input marble to the exit position) by turning the switch in either direction (assuming there is no marble in the exit position).
4. It's just more interesting to see the marbles inside the cannon, even if just when turning the switch to reload the cannon. The original design was a “black box” with no view into the inner workings.

This design is available on TinkerCAD if you want to modify it: https://www.tinkercad.com/things/6vibL3Pt9OL-alternate-switch-for-uhltimate-gauss-cannon-for-gravitrax

Also see my remix of the spring ends to use with this model at https://makerworld.com/en/models/206175#profileId-226324