This kind of puzzle is also called a logic puzzle, a Zebra puzzle or an Einstein puzzle.
In Quirk, the rows have letters, like A, B and C. Each column is one kind of thing, such as Pet or Color.
The rules
- Each row gets one choice from every column.
- Each choice is used once in its column, so no two rows get the same one.
- The clues tell you what goes together and what goes apart.
- You only need the clues shown. You do not need any facts from outside the puzzle.
- The puzzle is solved when every box is filled and every clue is true.
The clues come in a few types:
- "A has Cat" means Cat is in row A.
- "B has no Red" means Red is not in row B.
- "Dog and Green: same row" means Dog and Green go together in one row.
- "Owl and Blue: different rows" means Owl and Blue never share a row.
- "Exactly 1 is true" gives you 2 sentences. One is true and the other is false. Both true is not allowed.
- An "if" clue works one way. Take "If A has Red, then B has Cat". When A has Red, B must have Cat. Cat in row B does not prove that A has Red.
- A "before" clue uses the order shown for one column. The row with the first thing named must have an earlier choice in that order.
In the classic Zebra puzzle, there are 5 houses in a line and clues like "next to". Quirk keeps it smaller: 3 to 5 rows with letters, and 2 to 4 columns.
A worked example
There are 3 rows: A, B and C. The Pet column has Cat, Dog and Owl. The Color column has Red, Green and Blue.
The clues are: 1. B has Owl. 2. A has no Cat. 3. Cat and Blue: same row. 4. A has no Red.
- Clue 1 puts Owl in row B.
- Row A cannot have Owl, because B has it. Clue 2 says A has no Cat. So A has Dog.
- Only Cat is left in the Pet column, so C has Cat.
- Clue 3 says Cat and Blue share a row. Cat is in row C, so C has Blue.
- Row A cannot have Blue, because C has it. Clue 4 says A has no Red. So A has Green.
- Red is the only color left, so B has Red.
| Row | Pet | Color |
|---|---|---|
| A | Dog | Green |
| B | Owl | Red |
| C | Cat | Blue |
Here is a second example with the same rows, pets and colors. This time, the clues need a little more care.
The clues are: 1. Exactly 1 is true: A has Red, or B has Blue. 2. A has no Red. 3. If A has Cat, then C has Green. 4. B has Dog.
- Clue 2 says A has no Red. So the first part of clue 1 is false.
- Exactly 1 part of clue 1 must be true. So B has Blue.
- Row A cannot have Red or Blue. So A has Green, and C gets the last color, Red.
- Look at clue 3. C has Red, so "C has Green" is false.
- When the second part of an if clue is false, the first part is false too. So A does not have Cat.
- Clue 4 puts Dog in row B. Row A has no Cat and no Dog, so A has Owl.
- Only Cat is left, so C has Cat.
The answer is: A has Owl and Green, B has Dog and Blue, and C has Cat and Red.
Beginner techniques
Start with clues that name a row
A clue like "A has Cat" or "B has no Red" gives you a fact right away. Place those first. They often help you use the other clues.
Look for the last one left
Look for a box with only 1 choice left. Also look for a choice with only 1 box left in its column. Either way, you can fill it in.
Follow the links
A "same row" clue joins 2 things. As soon as you know where one of them is, the other goes in the same row.
Read an if clue backwards
If the second part of an if clue is false, the first part must be false too. This often rules out a choice.
2 rows, 2 choices
Say rows A and B can only have Red or Blue between them. Then they use up Red and Blue. No other row can have Red or Blue.
The same works for 3 rows with only 3 choices between them.
Common mistakes
- Reading an if clue both ways. "If A has Red, then B has Cat" does not mean Cat in B puts Red in A.
- Treating "Exactly 1 is true" as "at least 1". If both parts are true, the clue is broken.
- Using a choice twice in the same column.
- Thinking row A comes before row B. The rows have no order. A before clue only uses the order shown for its column.
- Guessing a box. Rule out choices first, and fill a box only when the clues leave one choice.
Questions
Is Logic Grid the same as the Zebra puzzle?
It is the same kind of puzzle. The famous Zebra puzzle has 5 houses and 5 kinds of things. Quirk uses smaller grids, with letters for the rows.
Did Einstein make this puzzle?
People often call it Einstein's puzzle. There is no proof that he made it.
What sizes are there?
Quirk has grids with 3 to 5 rows and 2 to 4 columns. Bigger grids come with more clues.
Does every puzzle have one answer?
Yes. The clues lead to one answer, and you can reach it without guessing.
Is there a timer?
No. Take your time. Your answers are checked using the clues.
Is it good for beginners?
Yes. The first puzzles have 3 rows and 2 columns. Quirk also has short lessons, hints, undo and reset.
Related puzzles
Playing it in Quirk
Tap a slot, then tap a sticker to put it there. You can also drag the sticker to the slot. Tap the same sticker again to take it out.
Hold a sticker to rule it out for that slot. It gets a red cross. The Rule out and Notes switches let you mark stickers without picking them. Notes are only reminders and do not count as answers.
