Sliding Puzzle 3×3

The 3×3 board holds eight numbered tiles and a single empty square, which is why it's often called the 8 puzzle. It looks simple, and it is quick, but it already has every idea the bigger boards use: you can only move what is next to the gap, and putting one tile home usually means moving two others out of the way first.

There are 181,440 ways to lay the tiles out that can actually be solved, and none of them is far from the finish: every one can be solved in 31 moves or fewer, and a typical shuffle needs around twenty. Most players need a few times that the first time round, and the count drops fast once the moves become familiar.

That makes this the board to learn on. Get 1, 2 and 3 into the top row, and the bottom two rows are a puzzle of their own with only five tiles to go. That last part is a loop: walk the gap round in a circle and the tiles turn with it until each lands in its spot. Watch the small dot in a tile's corner, which lights up when the tile is home.

The 3×3 also suits short breaks. A solve takes a minute or two, the shuffle is new every time, and your record of games played, games won and fewest moves is kept on this device. Nothing here is timed against anyone else; if you want a ranked puzzle, the daily 4×4 on the main page is the same for every player.

When eight tiles start to feel easy, the 4×4 adds a row and a column and turns a quick puzzle into a real plan.