Takuzu

Fill every empty square with a 0 or a 1, obeying three rules at once:

• No three of the same digit sit next to each other, across or down.
• Every row and every column holds equally many 0s and 1s.
• No two rows are the same, and no two columns are the same.

The counts down the left edge and along the top are the deduction aid. A row reading 0 3/3 has all the 0s it is allowed, so every remaining square in that row must be a 1. A pair like 1 1 forces a 0 next to it, because a third 1 would break the first rule.

The dark squares are given and cannot be changed. Click any other square to cycle it: empty, then 0, then 1, then empty again. Squares that break a rule are outlined in red and marked — a thick underline for three in a row, a double border for an unbalanced line, a dashed border for two identical lines — and the status line above names the rule.

Keyboard: arrow keys move around the grid, Home and End jump to the ends of the row, 0 and 1 write a digit, Space or Enter cycles the square, and Backspace empties it.

Every puzzle here has exactly one solution, and every step of the way there is a square you can work out for certain. You never need to guess.