Marblevator Baby Steps Revisited is an improved design of my previous Marblevator Baby steps. A video of the prototype is here: https://www.youtube.com/watch?v=yMNtGkjojUw. One of the improvements is that the stair steps ("Step 1.stl" through "Step 5.stl") no longer fall out when Marblevator Baby Steps Revisited is turned upside down (this improvement is thanks to grandkids and "how does it work" enthusiasts). Another is a small compartment designed to contain the "marbles" when not in use. Finally, the surfaces are smoother and more continuous than the previous design thanks to some of the design tools available in Autodesk Fusion 360. The design features two operating knobs, one in the front and one in the rear. Either knob can be rotated in either direction to operate Marblevator Baby Steps Revisited, so it is easy for left and right handers to operate. You will need to purchase at least one 8mm (5/16") diameter ball bearing to use as the marble. I probably forgot a file or two or something, so if you have any questions, please feel free to ask. Designed using Autodesk Fusion 360, sliced using Cura 2.3.1, and printed on both an Ultimaker 2+ Extended and an Ultimaker 3 Extended.