How to play a Binary puzzle
A Binary puzzle (also called Takuzu) is a logic puzzle with only zeros and ones. Fill every square with a 0 or a 1: never three the same in a row or column, as many zeros as ones in every line, and no two rows or columns alike. Each puzzle has exactly one solution.
Binary puzzle rules
- Fill every empty square with a 0 or a 1.
- Never put three of the same digit next to each other in a row, or one below the other in a column.
- Every row and every column contains as many zeros as ones.
- No two rows are the same, and no two columns are the same.
- Each puzzle has exactly one solution.
How to solve a Binary puzzle
Two in a row: the other digit on both sides
When two identical digits sit side by side, the squares on either side must hold the other digit. Two zeros next to each other? Then there is a 1 on both ends. This works across and down, and it is usually the first thing to look for.
The gap: 0 _ 0 means a 1 in the middle
If two identical digits have one empty square between them, that square must be the other digit. Otherwise you would get three in a row. So 0 _ 0 becomes 0 1 0, and 1 _ 1 becomes 1 0 1. These "sandwiches" are easy to miss, so scan for them regularly.
Count per row and column
Each line needs exactly half zeros and half ones. On an 8×8 grid that means four of each. Once a row already has four zeros, all its remaining squares are ones. Counting like this often finishes a line that the first two tricks could not.
Playing the Binary puzzle in Vellara
In Vellara you tap a square once for a 0, twice for a 1 and a third time to empty it again. Above the grid you can see how many zeros and ones the current row and column still need. If you break a rule, the squares turn red, so you spot a mistake at once. There is an Undo button, a Hint button (the light bulb) for when you are stuck, and Clear to start over. You can also make the squares smaller or larger, or fit the grid to your screen.
There are five levels. The easiest is a 6×6 grid where pairs and sandwiches get you through; the hardest is a 14×14 grid that asks you to look ahead. The stars show the hardest step of reasoning you will need, and the grid grows with them. Every puzzle is freshly generated and has exactly one solution.
A clock runs while you play, but there is no time pressure. Take as long as you like.
Binary puzzle FAQ
Is a Binary puzzle the same as Takuzu?
Yes. Takuzu is another name for the same puzzle with zeros and ones and the same three rules.
Do you need maths to solve a Binary puzzle?
No. You only count to half the width of the grid. It is pure logic: no sums, no guessing.
Why do some squares turn red?
Red means one of the rules is broken right now, for example three identical digits in a row or too many zeros in a line.
What should I do when I'm stuck?
Check every row and column for pairs, gaps and counts again. If that doesn't help, tap the Hint button (the light bulb).
Is the Binary puzzle free?
Yes. Vellara is free to download and play, and you don't need an account.
Download Vellara
Vellara is free for iOS and Android, needs no account, works offline and never sends you notifications.
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