ZEBRA: Einstein's Riddle

Five houses in a row. Who keeps the zebra? The world's most famous riddle, generated fresh every time. Exactly one answer, never a guess. Works offline.

Read one clue, cross out one square, and the answer comes to you.

Five houses stand in a row. Different nationalities, different colours, different pets. Who keeps the zebra? ZEBRA takes the most famous riddle format in the world and generates it fresh, every single time. You will never be handed the same puzzle twice.

■ Exactly one answer. Never a guess.

Every puzzle is checked by the built-in engine before you ever see it: · the solution is unique · it can be reached by deduction alone, with no trial and error Puzzles that fail either test are never published to you. When you are stuck, the only thing to question is your own chain of reasoning.

■ Deduction about position

An ordinary logic puzzle asks who goes with what. ZEBRA adds where.

· The green house is immediately left of the white house · Milk is drunk in the middle house · The Norwegian lives next to the blue house

Left, right, next to, at the end. Narrowing down a row is a different sensation from filling in a grid.

■ Features

· Four sizes: 3, 4, 5 and 6 houses. Five is the size of the original riddle · A daily puzzle — the same one for everyone, every day · Themes: Classic (nationality, colour, drink, hobby, pet), Forest, Street and Station · Draft mode for candidates you have not committed to · A hint that opens a single square when you are stuck · Solved count, streak, best times, per-theme records · Gentle mistake highlighting, on or off · English and Japanese

■ For you if

· You have solved Einstein's riddle or the zebra puzzle once, on paper · You want new puzzles, not one classic recycled · You want a game decided by logic, not by luck or reflexes · You want something quiet to think about on a train, offline · You would rather not have your concentration cut by advertising