1 — Helix (Pitch + Yaw)
A vertical helix of spheres rotates left↔right while a dot bobs up↔down.
The dot's vertical position at the instant you press SPACE sets
PITCH — centered on the red line = perfectly flat,
the best possible skipping angle. Edges = too steep, the rock plops in.
The helix's horizontal position at that instant sets YAW —
centered = straight ahead, off-center = drifts sideways.