Paritu – a logic puzzle of zeros and ones

How it works

Paritu is a binary logic puzzle: every cell gets either a 0 or a 1. Some cells are given and cannot be changed. You fill in the empty ones, and each tap moves a cell along: empty → 0 → 1 → empty. Once the grid is full, your answer is checked automatically.

• As many of each. Every row and every column holds as many zeros as ones when you are done — two and two on 4×4, three and three on 6×6.
• Never three in a row. Three identical digits may not follow each other, neither across nor down. Two are fine, three are not.
• On 6×6 only: no repeats. No two rows and no two columns are alike.

On this page Paritu starts in practice mode. The puzzle type is already chosen, so all you do is pick a difficulty — Easy, Medium or Hard — and begin. Play as many puzzles as you like; none of it is scored. The clock counts upwards: it tells you how long you took, and it is not running against you.

Every puzzle has exactly one solution, and every cell follows necessarily from the cells already in place. Paritu also appears in the Daily Sprint, in Endless, in Deduction Rush and in duels — here you can practise it on its own, at your own pace.

Tips & techniques

• Pair rule. When two identical digits sit next to each other, across or down, the cells directly before and after them must hold the other digit — otherwise there would be three in a row. This is almost always the first move.
• Gap rule. A zero, an empty cell, another zero: the gap has to be a one. The same holds the other way round for two ones.
• Line count. Once a row or column already contains half of one digit, every remaining cell in it is the other digit. You do not need to look at a single neighbour for this — just count.
• Unique lines. On 6×6 only: a filling that would repeat a row or column that is already complete is ruled out. It often helps when a line has just two cells left open.
• Trial. On Hard you will sometimes put a value in tentatively: if it leads to a broken rule, the other value is the right one. That is not guessing, it is a proof by contradiction.
• Change direction. When the rows give nothing more, look at the columns. Every rule applies across and down alike, and a newly placed cell usually opens the next step in the other direction.

Frequently asked questions

Do I ever have to guess in Paritu?

No. Every puzzle has exactly one solution and can be reached by reasoning alone. If you are stuck in one place, there is a rule you have not applied yet — look at a different part of the grid.

How do the difficulty levels differ?

Easy is a 4×4 grid where the pair rule, the gap rule and the line count are enough. Medium and Hard are played on 6×6, where in addition no two rows and no two columns may be alike. Hard gives you fewer cells to start from than Medium and may call for a trial here and there.

Are there hints when I am stuck?

Yes, in practice mode. A hint points to the next cell that can be worked out for certain — but never tells you which digit belongs there. Drawing the conclusion stays with you. Each puzzle comes with three hints on Easy, two on Medium and one on Hard.

Why does the rule against identical lines not apply on 4×4?

A grid that small has too few possibilities for the rule to add anything. It only arrives on 6×6, and there it is a real technique rather than a formality.

Does it cost anything, and do I need an account?

No and no. Paritu runs free of charge in your browser, and you can start playing straight away without signing up.