ZipRight tips: how to solve one-line number puzzles

ZipRight is a calm one-line puzzle. You draw a single line from 1, through every square, passing the numbers in order, without crossing a wall. It sounds simple, and the first levels are. By the harder tiers you'll want a method. Here's one.

The rules, once more

• Start at 1 and draw a line square by square.
• The line must pass through the numbers in order: 1, then 2, then 3, and so on.
• It must fill every square on the board.
• It can't cross a wall, and it can't visit a square twice.

Every puzzle has exactly one solution, which is useful: there are no alternatives to worry about, and the clues always point one way.

1. Look for forced squares first

Some squares leave you no choice. A square in a corner has only two neighbours, so the line has to use both of them as it passes through, unless the corner is where the line starts or finishes. A square with walls on its sides can be even more constrained. Find these first and draw them in lightly in your head.

2. Use the walls

Walls aren't just obstacles. They tell you which squares can't connect. Look along each wall and ask which pairs of neighbouring squares it separates, because the line can't join them. When you rule out a connection, the options for the squares on either side shrink.

3. Think in stretches between numbers

The line has to get from 1 to 2, then from 2 to 3. Count the squares between consecutive numbers. If 2 and 3 are right next to each other, that stretch is a single step. If they're far apart, the line has a long journey, and it will have to cover squares on the way. Think about which squares each stretch can reach, and which squares only one stretch can reach.

4. Don't leave an island

Every square must be filled, so avoid drawing a route that cuts a square or a small group of squares off from the rest. If a corner would be left with no way in, you've gone wrong earlier. This is the most common reason a line can't be finished.

5. Plan from both ends

You always know where the line starts. But it often helps to look at later numbers and work out how the line will have to approach them. If a high number sits in a tight spot, the line must enter it a particular way, and that tells you something about the squares before it.

6. Test short ideas

A little trial and error is part of the game. Try a route for a few squares, and if it leaves an island or blocks a later number, step back. Undo and clear are free, and hints are too, so experiment.

7. Take a break

If you're stuck, leave it and come back. A different pair of eyes, or just five minutes away, often shows what you missed. The puzzle isn't going anywhere, and there's no timer pushing you.

The levels

ZipRight has 6,000 levels in four tiers of 1,500: Easy, Medium, Hard and Expert, on boards from 5×5 to 8×8, with difficulty rising level by level. The first 50 levels, the first level of each tier, a free puzzle every day, hints and every theme are free. One optional purchase unlocks the rest.

See ZipRight, or take a look at our other calm puzzle games. If you like planning ahead, try how to play PathRight.