Lunar Libration Diagram (2D): Kepler Orbit & Wobble Trace

Tidal locking is often described as "the Moon always shows Earth the same face," but that is only true on average. This 2D companion simulator computes the real orbital mechanics behind that near-face directly in the plane: every frame it solves Kepler's equation for the Moon's true anomaly, compares it against the Moon's perfectly uniform tidally-locked spin angle, and turns the mismatch into a live sub-Earth marker on a flat moon disc plus a running libration-diagram trace — the (longitude, latitude) wobble chart real lunar observers use. Because the orbital speed genuinely varies with distance under Kepler's second law whenever eccentricity is non-zero, and the spin axis stays fixed in space while the Moon's orbital position sweeps around Earth, the sub-Earth point drifts back and forth by several degrees each orbit in both longitude and latitude — together letting Earth-based observers map close to 59% of the lunar surface with the naked eye. Adjust eccentricity and axial tilt to grow or vanish the wobble, and switch to the libration diagram to watch the closed Lissajous-like loop it traces every orbit.