Are the two shapes the same (rotated) or different (mirrored)?
Two shapes appear side by side, each made of five squares. The right one is always the same piece as the left one: either just turned (SAME) or flipped into its mirror image and then turned (DIFFERENT). The turn is random: none, a quarter turn either way, or a half turn. Pieces that look identical in a mirror are never used, so every round has exactly one correct answer.
Tap SAME or DIFFERENT before the time bar at the top of the board runs out. The bar is blue at first, turns amber when about a third of the time is left and red in the last 15%.
The first pair gives you 5 seconds. Each correct answer adds 1 to your streak and takes 0.15 seconds off the next limit, down to a floor of 2 seconds, which you reach after 20 correct answers. After a correct answer there is a half-second pause before the next pair appears, and the clock does not run during it.
A wrong answer or an empty time bar ends the game at once, and the correct button lights up so you can see what the answer was. Your streak is your score: the best one is saved on this device, and from the game-over card you can save it to the Hall of Fame or start a new game.
Goal: the longest streak.
This is a mental-rotation test, and the fast way to read it is to ignore the shape as a whole and lock onto one telltale feature. Find an asymmetric detail — a notch, a tail, the limb that points off at an odd angle — and ask only what happens to that one feature. If you can spin the left shape in your head and that detail lands where the right shape has it, they are the SAME.
The giveaway of a mirror is "handedness": a rotated shape keeps the same chirality, like turning a right hand, while a mirrored one flips it into a left hand no amount of turning can fix. When the timer is tight, trust the first clean read — if a feature that should be on the inside of a curve is suddenly on the outside, it is DIFFERENT, and second-guessing a correct snap judgement is how streaks die.
Only six pieces are ever used — the five-square pieces that have a distinct mirror image, usually named after the letters they resemble: P, F, Y, N, L and Z — and they are far from equally common. Because of how the pieces are generated, the P (a 2×2 block with one extra square attached) shows up in about half of all rounds, the F and the Y in roughly one round in seven each, the N and the L in about one in twelve, and the Z in only about one in 25. The P therefore deserves its own shortcut: look from the square block toward the extra square and note whether the extra square sits flush with the block's left side or its right side. Turning the piece never changes that answer; a mirror always does.
A quarter of all rounds use no turn at all, so the right shape is either an exact copy (SAME) or a plain left-to-right reflection (DIFFERENT), and another quarter use a half turn, where a mirrored piece looks like a top-to-bottom flip. Check those easy cases first. For quarter turns, use a walking test that works on all six pieces: take the longest straight row of squares, walk along it from the end farthest from the squares that stick out, and note whether the first one you meet is on your left or your right. Ignore size, because each shape is scaled to fill its half of the board and a turned piece often looks bigger or smaller. Finally, never let the bar run out: a timeout ends the run just like a wrong answer, while a guess still survives half the time, and each round's answer is picked fresh, so a string of SAMEs does not make DIFFERENT due.