Marble Race 3D:
First to the podium

Every track here is a chute swept along a descending centreline, and all of them share one collision model. What differs is the path: a constant-radius helix, a tightening funnel, a slalom whose axis slides side to side, an oval speedway with two hairpins, an hourglass pinched at the waist.

Those differences decide the character of the race far more than any physics setting. A funnel accelerates the pack and squeezes it together, which produces close finishes. A wide helix lets a fast marble get clear early. A slalom keeps forcing the field across each other, which produces constant position changes and few clean leads.

One constraint runs through all of them: the centreline never goes momentarily vertical, because the chute’s lateral axis is derived from the horizontal perpendicular of the tangent, and a vertical tangent has no defined lateral axis. Every shape is built from a circulation term with a positive lower bound on its radius, which guarantees the chute never twists through itself.

In a flat race, the pack is always visible and the leaderboard is a convenience. In a 3D track, marbles pass behind geometry, drop out of frame on the far side of a bend, and reappear somewhere else. The visual is more dramatic and considerably harder to read.

The leader-sings rule is the compensation. Whatever the camera can see, the melody is coming from first place, so the audio is a continuous readout of who is winning even when the picture is ambiguous.

That is also why the pack click has to be genuinely quiet. It exists to make the field feel populated, and the moment it competes with the leader’s melody the readout stops working and the mode loses the thing that separates it from every other marble race.