Phases

Move the Sun and Moon until both views match the goal — phases come from the Sun-Earth-Moon angle, not Earth's shadow.

How to play

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

Controls

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

Game modes

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

Tips & strategy

• 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

What you'll learn

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.

About Phases

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.

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