Fifteen Slide Unblocked

Fifteen Slide is the sliding puzzle that has been sold in toy shops for well over a century, rebuilt with chunky yellow 3D cubes. Fifteen numbered blocks share a 4x4 frame with a single empty slot, and the only legal move is to push a neighbor into that slot. It sounds limited, yet the scrambled board can take real thought to untangle. Alexander Bazhanov’s version keeps a move counter, a clock and a local high score list, and it plays unblocked with keys, a mouse or a touch screen.

Starting a Game

Press Play and a short countdown appears; behind it the blocks are being shuffled. The timer begins at GO, and the counter under the frame ticks up with every slide.

Only a block sharing an edge with the empty space can move, and it moves straight into it. There are no diagonal slides and no sliding several blocks at once. With the arrow keys, the block next to the gap travels in the direction of the arrow.

A solved frame runs 1 to 4 on the first row, 5 to 8 on the second, 9 to 12 on the third and 13 to 15 on the last, ending with the empty slot. Finish and you are asked for a nickname; saving it puts your result on the High scores table. You can bail out to the menu any time with the arrow in the corner.

With a mouse, a click-and-drag over the frame swings the 3D view around, which helps if the angle hides a number.

Fifteen Slide controls

To do this	Keyboard	Mouse	Touch
Push a neighboring block into the gap	Arrow keys (the block beside the gap moves in the arrow's direction)	Click a block next to the gap	Tap a block next to the gap
Rotate the 3D view	—	Hold the button and drag across the board	—
Begin a game or view high scores	—	Click "Play" or "Scores"	Tap "Play" or "Scores"
Record a finished solve	Type a nickname	Click "Save"	Tap "Save"
Go back to the main menu	—	Click the "Menu" arrow	Tap the "Menu" arrow

A Reliable Solving Method

Speed comes later. First learn a method that always works.

Stage 1: the top row. Bring 1, 2 and 3 into place one at a time. The 4 is awkward because it sits in a corner. Put 3 in the top right corner with 4 directly beneath it, bring the gap to the square left of 3, then slide 3 left and 4 up. After that, the top row is off limits.

Stage 2: the second row. Repeat the same idea for 5 to 8, using the corner trick for 8. Now just a 2x4 strip at the bottom is still in play.

Stage 3: the remaining strip, column by column. Solve 9 and 13 together as a vertical pair in the left column, then 10 and 14, using the same parking trick as before.

Stage 4: the final three. With 11, 12 and 15 left in a small square, cycling the gap around that square rotates them until they fall into order.

The key idea behind every stage is the loop. Walking the gap around any 2x2 block rotates the three tiles inside it and leaves the rest of the board alone.

Moves Over Minutes

The scoreboard ranks by move count, not time. A slow, careful solve can easily beat a fast, messy one, so plan before you slide. If you enjoy step-by-step logic like this, try Tower of Hanoi or the number-merging grid of 2048.