How to play the Loop Puzzle
Read it top to bottom and you can play. The ways of solving in the second half come in order of difficulty.
1What is a loop puzzle?
A board of dots, on which you join dot to dot with lines to make one loop. A number in a square says how many of its four sides the loop runs along. When one loop closes and meets every number, it is solved.
When it closes, the loop turns violet and its inside fills with colour.
Every puzzle has one loop only, reached step by step from the numbers without guessing.
2Three rules
- A number has that many of its sides on the loopA square with no number can have any
- The loop never branches or crosses itselfEvery dot has 0 or 2 lines, and the loop never touches itself
- It is solved when it is one closed loopTwo or more loops will not do
3Reading the numbers
A number is how many of the square's four sides have the loop on them. A 0 has none; a 3 has all but one.
A 2 can be two sides that meet at a corner or two opposite sides. Which ones, you work out from around it.
A × in the pictures marks a side with no line.
4Controls
| Do | What happens |
|---|---|
| Slide | Slide from dot to dot to draw; slide along a line to take it off |
| Tap | Tap a side to draw a line or take it off |
| × | Mark a side with no line: switch to × with its button, or right-click on a computer |
| Undo | One step back (Ctrl + Z on a computer) |
| Hint | How to think first, then where, then the line. Lines drawn by mistake come first. |
| Start over | Press twice to clear every line |
| Keyboard | X switches between lines and × |
A wrong line is not pointed out as you go. Only a square with more lines than its number, and a dot with three lines or more, turn red.
5Counting
The easy puzzles need nothing more than this. In the pictures, what the step decides is lit yellow.
Cross every side of a 0
No line runs along a 0, so cross all four of its sides first. The same goes for any number: once it has its lines, cross the rest; when the sides left are just as many as the lines it still needs, draw them all.
A dot has 0 or 2 lines
The loop never branches, so a dot has no lines or two. A dot with one line must go on: if only one way is left, draw it. A dot with two lines has the rest crossed. A dot with only one side left uncrossed is a dead end, so that side is crossed too.
Never close a small loop
There is only one loop. If a side would close a loop while there are other lines on the board, cross it. Watch for the two ends of a line reaching neighbouring dots.
6Corners and 3s
The normal puzzles ask you to read what happens at a square's corners. A dot in a corner of the board has only two sides, so they are both lines or both crossed.
A 3 in a corner
If both sides at the corner were crossed, only two would be left, too few for a 3. So both corner sides are lines.
A 1 in a corner
Both corner sides drawn would be two lines, more than 1. So both are crossed.
Two 3s side by side
The side between them and the two outer sides are all lines: without the middle one the two 3s would close a small loop. The sides that carry the middle line on, above and below, are crossed.
Two 3s corner to corner
The dot where they meet can take only one line from each 3. So each 3 has its two sides away from that dot drawn.
A line into a 3's corner
Say a line comes into a corner of a 3 from outside. That dot can take one more line, so only one of the 3's two sides there is drawn. The 3's other two sides are lines, and the other way out of that dot is crossed.
A 2 in a corner
The edge sides of the squares next to it are both lines. If the corner sides are drawn, the 2's other sides are crossed and the line has to go on along the edge. If they are crossed, the 2's two inner sides are drawn, and they too can only go on along the edge.
7Inside and outside
The hard puzzles ask you to think about the inside and the outside of the loop. Every square is either inside or outside, and beyond the board is outside. Between two neighbouring squares that differ there is a line; between two the same, a cross.
A square on the edge of the board is inside if its edge side is drawn, outside if it is crossed. Follow the lines and crosses from there and the inside spreads. Even before you know which, knowing that two squares are the same, or differ, is enough.
A number is also how many of its four neighbours (beyond the board counts too) differ from it. A 3 known to be outside has three neighbours inside.
8Trying a line
On an Oni puzzle there are moments when none of the steps above takes you further. Then draw a line on a side for a moment and follow what it decides. If something cannot be - a number with too many lines, a dot with three, a small loop closing - that side is crossed. You can try a cross the same way.
Undo takes a tried line off again.
9Grades and stars
| Grade | Size | Steps it needs | Target time |
|---|---|---|---|
| Easy | 6×6 | Counting only | 90 seconds |
| Normal | 8×8 | Up to corners | 4 minutes |
| Hard | 10×10 | Up to inside and outside | 8 minutes |
| Oni | 12×12 | Up to trying a line | 15 minutes |
Three stars: ★solve it ★no hints ★within the target time.
10Ways to play
Today's puzzle
- The same 10×10 for everyone, new at midnight Japan time
- Your first solve of the day goes on the ranking
- Each hint adds 30 seconds
Solo
- Four roads of a hundred - easy, normal, hard and Oni - ten to a chapter
- Start on any road; along it they get a little more work each time. The first one you have not solved and the two after it are open
- The first 30 of each road, 120 in all, are free
- Past those, one ticket opens the next puzzles on that road (5 easy, 4 normal, 3 hard or 2 Oni), or the Lounge Pass opens them all
11Tips
- Start where it is easiestLook for 0s, the board's corners and 3s together first. The first lines and crosses usually come from there.
- Follow the endsEvery end of a line goes on somewhere. Look at the dot at an end alone and the next line is often plain.
- Cross freelyCross a side as soon as you know it has no line. The more crosses, the easier the dead ends and the numbers' last sides are to see.
- Stuck? Inside and outsideSpread what you know is inside or outside from the edge of the board, and the lines you missed show up.
12Questions
Is it free?
Yes. Nothing to sign up for: it plays in the browser at once. 120 of the 400 puzzles are free, and the rest come with the Lounge Pass or a ticket. Today's puzzle and its ranking are free too. Signed in with Google, tickets come free as a daily gift, for solving today's puzzle, and more.
Can I play on a phone?
Yes. In the browser on a phone, a tablet or a computer. Nothing to install.
Is it the same as Slitherlink?
It has the same rules. Slitherlink is a registered trademark of Nikoli, so it is called the loop puzzle here.
What is the Lounge Pass?
A subscription that takes the ads away in every game and opens everything that would need the Pass or a ticket. Here, all 400 puzzles. Without it, one ticket opens the next puzzles along a road (5 easy, 4 normal, 3 hard or 2 Oni). ¥500 a month or ¥5,000 a year, tax included, with a 7-day free trial the first time. The first 100 founding members pay ¥300 a month or ¥3,000 a year, for as long as they keep it.
Does every puzzle have one answer?
Yes. Every puzzle has a single loop, reached step by step from the numbers without guessing. Only the Oni ones ask you to draw a line for a moment and see that it cannot be.
Can I see the answer?
While you play, a hint tells you how to find the next line. If you need more, it shows where, and then draws it. Lines drawn by mistake come first.
What happens if I go wrong?
You are not told on the spot. Only a square with more lines than its number, and a dot with three lines or more, turn red. When the loop closes and meets every number, it is right.