A cratered Moon disc reconstructed as a sphere in the fragment: for every lit pixel z = √(R² − x² − y²) gives the surface normal, and the shade is dot(normal, sunDir). A sun direction turning steadily through the synodic month sweeps the terminator new → crescent → quarter → gibbous → full and back, softened into a penumbral band so the edge stays velvet, while the unlit hemisphere keeps a faint blue earthshine — the ashen light of the near-full Earth — strongest around new Moon. Procedural maria darken the lowlands and a two-scale crater field bumps the normal so real relief rakes into shadow along the terminator. Move the pointer to place the Sun by hand, scroll to advance the Moon's age, press for a gentle libration nod. Calm, tone-mapped, capped below white.