Mirrorturn is a spatial puzzle: two models made of balls and sticks stand side by side, both built from the same balls. You turn them and decide whether it is the same model, just turned differently, or its mirror image - free in the browser, no sign-up.
Before every run you pick a profile: Beginner with twelve rounds on three levels, Standard with fifteen rounds on five levels, or Expert with nine rounds on the three top levels and a clock. Whether a pair is the same or mirrored is drawn afresh every round; only one thing is certain: never more than three equal answers in a row.
The five levels are called Easy, Medium, Hard, Very hard and Master. First the models get bigger: four balls on a middle ball, then a short arm is added, then a short and a long one. From the Hard level on the letters on the balls are gone, on the Master level the colours too, and there only model A can be turned - model B stands still, you turn it in your head. Every correct answer is worth 100 points, 60 with a nudge; on the top two levels there is no nudge. Wrong answers cost nothing. In the Expert profile a clock of 20 seconds runs for every round: if it runs out, the round doesn’t count, you still see the answer, and the next round waits until you start it. At the end there is a summary card; a new run only begins when you start it, and it asks for the profile again.
Spatial thinking: you practise turning things in your head and spotting a mirror image even when it is twisted round. In chemistry this property is called chirality – from the Greek word for hand, because left and right hands are exactly such a pair.
Yes, five small molecules from chemistry, shown in simplified form: the balls are atoms, the sticks their bonds. On the highest levels only the colours and letters are left out - the model stays the same real molecule, and after the answer colours and letters are visible again. You don’t need to know any chemistry.
The Beginner profile if you want to get to know the game: colours and letters help, and both models can be turned. The Standard profile if you want to see how far you get as the aids fall away one by one. The Expert profile if you want the hard levels under time pressure.
No. Mirrorturn is unranked: the points count only for you and stay on the screen. There is no streak and no leaderboard, and your choice of profile is not stored either.
Yes. On a phone you turn a model with your finger, on a computer with the mouse or the keyboard. On the top levels the balls are small on a small screen; zooming helps.
No and no. Mirrorturn runs free in the browser without signing up. You only need a connection, because every answer is checked on the server.
The full guide with a worked example: Mirrorturn rules and guide.