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.
A run has twelve rounds on three levels, four rounds per level. On every level exactly two pairs are mirror images and two pairs are the same model turned differently — and nothing gives away the order.
The three levels are called Easy, Medium and Hard, and the models get bigger: first four balls hang on a middle ball, then a short arm is added, and finally a short and a long one. Every correct answer is worth 100 points. Take a nudge and a correct answer is worth 60. Wrong answers cost nothing. At the end there is a summary card; a new run only begins when you start it.
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, three small molecules from chemistry, shown in simplified form. You don't need to know any chemistry.
No. Mirrorturn is unranked: the points count only for you and stay on the screen. There is no streak and no leaderboard.
Yes. On a phone you turn a model with your finger, on a computer with the mouse or the keyboard.
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: same or mirrored?.