How to make an animated treadmill

Make sure to have claimed a plot, be in 'Create' mode, and press the 'Build' button on the left side of the screen until you see a toolbar appear on the right side of the screen.

Using 4 parts, make a single platform with a hole in the center.

Grab another part, an place it in the center of the hole. This will be the 'treadmill'.
Grab a wedge or other shape to animate it downwards, and duplicate it. Place it on top of your treadmill block.

Arrange the wedges to expand beyond the treadmill block's front and back.

Select your shapes and merge them into one object. Then select that object and set its collidable off.

Move your shapes lower, on top of the treadmill block but below the platform, so it's not visible on top of the platform when it animates.

Open that object's Code Builder by clicking the </> button on the right toolbar. Now we're going to animate it.
In Code Builder, go to 'Events' and grab at start. Then go to 'Control', grab do forever and place it below at start.

This ensures the Code runs at the start of the game, and runs the whole time the game is playing.

8. Go to 'Motion' on the left and grab tween position in plot to x : - y : - z : - in -- seconds. Change ' to' to ' by', and place it in between do forever and end.

To animate this object downwards, insert a negative value in the x axis.

You should always check which axis you are moving the object on by using the move tool and checking its position. The three values represent x, y, and z respectively.

Go back to 'Control' and grab wait -- seconds. Set it to the duration you've written in your tween position block.

This ensures the block finishes moving before running the next code.

11. Duplicate your tween position block, put down 8 in its x axis. For the duration, set it to below 0.1 seconds.

This tweens the block back to its original position quickly without being too obvious so it looks like a seamless animation where it continuously moves down.

12. Grab another wait -- seconds and set it to the duration of your newest tween position block.

Save your code, and close the Code Builder for that object. Now in your plot, select your treadmill block, and open Code Builder.

In Code Builder for your treadmill, go to 'Events' on the left and grab when touched by player every -- seconds.

Set your every -- seconds to below 1 second, so the code takes effect without delay.

Now go to 'Motion' on the left and grab change velocity x : 0 y : 0 z : 0. Input the same value as your triangles' movement in the x input.

This block makes anything that is on the treadmill move the direction you tell it to. In this case, downwards.

Save your code, and when you press 'Play', you will see your treadmill animating and your player will move downwards when on it.