Phases

A split screen shows the orbital geometry on one side and the Moon as seen from Earth on the other. Each puzzle asks for a specific phase or an eclipse. Rotate the Sun and Moon around Earth until the geometry produces it and both views agree, then you've solved it.

• The lit fraction depends on the Sun-Earth-Moon angle (elongation)
• Eclipses require true alignment of all three bodies
• The sky view updates live as you move the bodies

• Desktop: drag the Sun and the Moon around Earth
• Phone & tablet: drag the Sun and Moon with your finger

• Daily: one shared challenge each day
• Practice: endless fresh phase and eclipse goals

• A full moon sits opposite the Sun; a new moon sits between Earth and Sun
• For quarter phases, aim for a right angle at Earth
• Eclipses need exact alignment, nudge slowly to hit it

Phases makes lunar phases and eclipses click by linking the Moon's orbital geometry to the view from Earth.

• Skills: astronomy, lunar phases, eclipses, orbital geometry, spatial reasoning
• Best for: roughly grades 5–10 (ages 10–16)
• For parents & teachers: clears up one of the most commonly misunderstood topics in science.

A split screen showing the orbital geometry beside the Moon as seen from Earth is the standard cure for the standard misconception about lunar phases.

Rotating the Sun and Moon yourself to produce a named phase or an eclipse is the original method.

Phases are caused by which part of the lit hemisphere faces us, not by Earth's shadow — the shadow explanation is what a lunar eclipse actually is, and confusing the two is near-universal. Seeing both panels move together is the only thing that reliably separates them.

Phases is an original astronomy puzzle that makes lunar phases and eclipses click by linking orbital geometry to the view from Earth. It's free to play in your browser.

A free, original browser game on PlayPendium. No download, no install.