Number sliding puzzle rules: tiles, gap and goal

Move a numbered tile horizontally or vertically into the single empty square. Solve the puzzle by restoring ascending row order, with the empty square in the bottom-right corner.

Understand the empty square

Every legal move swaps the gap with a tile sharing an edge with it. A diagonal neighbour cannot move directly into the gap. A tile farther along the same row also cannot jump over the tile between them. Think of the empty square as the space you transport around the board to make the next desired move possible.

A corner gap has fewer immediate neighbours than a gap in the middle. Before moving a target tile, find the gap and ask which side of the target it must reach. Much of solving consists of bringing that space to the right place without undoing a completed section.

Know the destination

For a small square board, read the goal left to right across the top row, continue across the next row, and leave the final square empty. The numbers are labels for destinations, not values to add together. A tile belongs in one particular cell of the target layout.

Here is the goal for the eight-tile puzzle. A dot represents the empty square, not an extra numbered tile.

1 2 3
4 5 6
7 8 .

A board is not finished merely because its rows each increase. The complete order and the final gap position both matter. Keep the target layout in mind so that you can tell a useful move from a move that merely looks tidier.

Follow a short legal example

Consider this position:

1 2 3
4 5 6
. 7 8

Move seven left into the gap, then eight left into the new gap. Both moves are legal because the moving tile shares an edge with the empty square at that moment. Notice that the gap travels right while the numbered tiles travel left.

This opposite movement is why instructions can be confusing. In this guide, naming a tile means moving that tile into the current gap. If you instead use arrows for the gap's direction, state that convention before practising a sequence.

Start planning in small sections

1. Locate the next tile you want to place.
2. Identify the side where the gap must be for that move.
3. Route the gap there using neighbouring unsolved cells.
4. Move the target tile into the gap.
5. Check which completed cells the following route must preserve.

Do not insist that every move bring a number closer to its destination. Sometimes the gap must go around a target, or a tile must move aside temporarily so another can pass. Judge a short sequence by its resulting arrangement, rather than judging every individual move in isolation.

Common rule mistakes

The number sliding puzzle differs from the traditional rectangular-block escape puzzle. You are not moving a large named piece toward an exit. You are rearranging equal-sized numbered tiles around one gap. It also differs from Sudoku: no new numbers are written, and each existing tile moves physically through adjacent spaces.

Another frequent misunderstanding is treating every arbitrary arrangement as solvable. Legal moves preserve a parity condition, so some manually assembled layouts cannot reach the standard goal. If only a swapped pair remains, repeated shuffling is not always the answer; the board's solvability needs to be considered.

Practise the movement convention

Before timing yourself, choose a nearly solved board and describe each move aloud. Say which tile enters the gap and where the gap ends up. This builds a reliable connection between the visual board and any later written solution sequence.

Once those moves feel natural, practise making a small loop in an unsolved area and observe how the tiles rotate. Repositioning the gap without disturbing a solved row is a useful early skill, and it gives a clear purpose to moves that initially seem to go sideways.

Where to play

YIGE / 一格华容道 is a number sliding puzzle for HarmonyOS, with boards from 3×3 through 6×6. Its 25,000-level campaign unlocks sequentially for free. Campaign and daily play share three free hints per day; optional Pro adds unlimited hints in those modes and free level selection.