The Case of the Seven Reflections: A Fairy Detective Optics Mystery

An interactive optics mystery for kids ages 9–12 who like reading and stories. Plays in a browser, about 1–2 hours.

Your child plays a fairy detective investigating an emerald stolen from the seven dwarves' cottage. Each dwarf witnessed the theft — but each saw the thief reflected in a different kind of mirror, so each gives a different description of who they saw. To untangle the testimonies and identify the thief, your child has to understand how plane, convex and concave mirrors actually behave.

The optics is built into the mystery rather than taught alongside it. The dwarves' contradictory accounts only resolve once you understand which mirror types invert images, which change apparent size, and which can do both depending on distance. Along the way, the queen's magic mirrors explain themselves in conversation — one of them is a fish, one is a sphinx — the classic "why does a mirror reverse left and right but not up and down" riddle gets answered, and a spoon, concave on one side and convex on the other, becomes a tool for testing all of it at the kitchen table.

How the case actually works

• Interview everyone. Seven dwarves, Queen Agnes, and your own client — ask each of them what they saw, who they suspect, and what they wanted with the emerald.
• Keep a suspect board. A summary screen collects all seven testimonies in one place, and you cross suspects off as the evidence rules them out. Nine names; one of them did it.
• Get stuck on purpose. Four hints, each one further than the last, and none of them give away the answer. The first tells you to trust the plane-mirror witnesses first, because plane mirrors show things accurately. The last still leaves the final step to your detective.
• Make the accusation. Name your thief in front of everyone. Get it wrong and a witness will contradict you, out loud, from their own testimony — and you can play it off as a joke and think again. There's no losing screen, only a case that isn't solved yet.

What it covers

• The three main mirror types — plane, convex and concave — and what each one does to an image's size and orientation
• A brief introduction to how light reflects and how our eyes interpret what comes back
• The left/right reversal puzzle, and what's really going on
• The classic brainteaser: how tall does a mirror have to be for you to see all of yourself in it? (The same question turns up in Light: A Fairy Tale, worked through with the geometry.)
• Four optional detours into PhET's free Geometric Optics simulation from the University of Colorado — one per mirror type, plus one for when it all gets confusing — each with step-by-step instructions for what to click and what to watch for

This is a companion to a class or unit on optics, not a complete curriculum. It works alongside any introduction to reflection and mirrors.

What you'll get

A PDF with a link to the game's webpage. From there your child can play directly in any browser — phone, tablet or computer — or download an offline version for laptops and desktops.

The PDF is ready the moment you check out — the download button is on the confirmation page. Your order confirmation email also has a View Order and Downloads button, which takes you back to your order page to download it any time.

Practical details

• Plays in about 1–2 hours, in one sitting or several
• Reading-heavy — around 13,000 words, about the length of a short chapter book. Best for kids who enjoy stories and text.
• One mystery with a single solution; not designed for replay
• More fun with a few household items on hand: a mirror, a reflective spoon (the more spherical the better), and paper and a pen for detective notes. The game works without them, but they help.

Accessibility

• The game is entirely text-based and reading-heavy. Kids who prefer audiobooks or have reading difficulties will likely need a parent or sibling to read aloud.
• Self-paced throughout — no timers, no audio cues, no fast reflexes required.
• Plays with mouse, trackpad or touch. No keyboard shortcuts required.
• Text size scales smoothly across phones, tablets and computers, with a comfortably large minimum on small screens.
• The hands-on spoon experiments are optional — the game can be completed without them.
• Not formally tested with screen readers.

A note about the story

The mystery is loosely inspired by the public-domain Snow White fairy tale as the Brothers Grimm told it. The princess character is named Fay, and the setting is an original take on the seven dwarves' world — no affiliation with Disney or any other adaptation.

About the author

Sarah Allen tutored math and physics for twenty years before becoming a full-time writer. She has a physics degree from the University of Washington (graduated with college and departmental honors) and a master's in Cognition and Learning from Columbia. Her goal is to write the sort of physics books she would have wanted as a kid.

Ages 9–12 · Browser game, about 1–2 hours · ~13,000 words · Delivered as a PDF with the game link