🧪 Marble Machine — Motorized Elevator & Gravity Track (2D)

The mechanics are related but not identical: the 3D version animates marbles moving along the track at a fixed rate regardless of slope. This 2D version instead integrates real tangential-gravity dynamics — marbles speed up on descents and slow down on climbs, exactly like a real ball on a track — plus a motorized elevator segment and adjustable rolling friction.

The track is built so total height dropped on the gravity section exceeds any local climb, so a marble entering with the elevator's exit speed has enough momentum to crest every bump under normal friction settings; a small speed floor also represents the vibration real ball bearings get from a running machine, so they never freeze in place.

The elevator moves marbles at a constant motor-driven speed — that part is a mechanical drive, not gravity — exactly like a real paddle-belt or bucket elevator lifting balls against gravity. Once a marble reaches the top it is released onto the free gravity track, where its motion is entirely determined by the physics loop each frame.

Gravity sets how strongly the track's downhill sections accelerate a marble and uphill sections decelerate it. Friction is a rolling-drag coefficient that continuously removes speed proportional to the marble's current velocity, so higher friction produces a slower, more damped lap.

Every marble runs its own independent physics loop, so the displayed average track speed is the mean instantaneous speed of all marbles currently on the gravity section — adding a marble that just left the elevator, or one crossing a climb, shifts that average until they redistribute around the loop.