Moon Phases Diagram (2D)

This 2D simulator draws the Sun–Earth–Moon system from directly above: sunlight arrives as parallel rays from one side, the Moon orbits Earth once every 29.53 days, and the sunlit hemisphere of the Moon is always shaded to match. A companion Earth-view disc translates that geometry into what a stargazer actually sees in the sky — a thin crescent, a half-lit quarter, or a full bright circle. Drag the day-of-month slider or press Play to animate a full lunar month, and watch the live readouts track the Sun–Earth–Moon angle, the illuminated percentage, and the countdown to the next full and new moon.