The rules of Zip
You draw a single path through the grid. It has to follow four rules:
- It moves up, down, left or right, one cell at a time, never diagonally.
- It visits every cell exactly once, so it can't cross itself.
- It starts on 1, passes the other numbers in order, and ends on the highest number.
- It can't cross a wall, the thick line some boards draw between two cells.
Each practice board on this page has exactly one answer. The numbers tell you where the path has to go, and the empty cells are where all the thinking happens.
How to solve Zip
Most mistakes in Zip don't show up until the end, when one cell is left over with no way in. These five tips catch them early. Dashed red outlines mark the cells each tip is about.
1. Corners have two doors
A corner cell touches only two others. Unless the path starts or ends there, it has to come in through one and leave through the other. Draw those two moves early and the edges of the board start to fill themselves in.
2. Never strand a cell
Before each move, look at the cells you're passing. If one of them is about to lose its last two open neighbors, the path can never reach it. Here the corner is cut off, so this route is already wrong.
3. Don't split the board in two
The path can only be in one place at a time. If it walls off two separate pockets of empty cells, it can fill one of them and then it's stuck. Keep the empty cells in one connected piece.
4. Count steps on a checkerboard
Color the grid like a checkerboard. Every step lands on the other color, so the number of steps between two numbers is even when they sit on the same color and odd when they don't. When you plan a detour between two numbers, this tells you whether it needs an odd or an even number of steps.
5. Walls make new corners
A wall takes a neighbor away. A cell in the middle of the board with two walls beside it has only two ways in, just like a corner, so the path through it is decided.