Daily Sliding Puzzle

Daily Sliding Puzzle gives the Sliding Puzzle specialist its own date-stable challenge without changing the platform’s main Today’s 6. Everyone using the same local calendar date gets the same deterministic starting board. If you leave before finishing, the current grid, move count and active-time state are restored from browser-local storage when you return.

One deterministic board for each date

The Daily generator combines the calendar date with the same local deterministic engine used by seeded Practice. It does not call a remote puzzle API and does not download a daily level file. Starting from the completed board, the engine performs a legal scramble sequence. That guarantees the final state remains reachable from the solved position.

The date controls both the scramble and the mode. The cycle intentionally favors the classic 4×4 15 Puzzle while still scheduling regular 3×3 and 5×5 boards. In a six-day cycle the pattern is Classic, Easy, Classic, Easy, Classic, Challenge. Over a normal 365-day year this produces 183 Classic days, 122 Easy days and 60 Challenge days.

Why Daily does not use a random permutation

A purely random ordering of the numbers can violate sliding-puzzle parity and create an impossible board. A Daily challenge should never fail because the site accidentally served a state that cannot be solved. V0.115 therefore generates Daily positions through actual legal blank moves from the goal and independently verifies the final state and reverse solution path.

That design also makes the challenge reproducible. Given the same date and version contract, the generator returns the same board. QA can enumerate an entire year, validate every tile set, replay each stored reverse path, check parity and confirm that dates do not silently collapse onto the same starting state.

Board-size rhythm

Easy days use the 3×3 eight-puzzle format. These are short enough for exhaustive shortest-path analysis, so the game can display the true minimum number of moves for the starting position. Classic days use 4×4, the traditional fifteen-tile format. Challenge days use 5×5 for longer spatial planning.

For the larger modes the application deliberately does not call the scramble length a minimum. The generator always stores a legal solution path because reversing the scramble solves the board, but another route may be shorter. Daily history therefore records actual moves and time without inventing an optimality claim.

Daily history and specialist streak

Finishing a Daily Sliding Puzzle writes a record for that date into slidingPuzzleStats.daily.history. The record includes the board level, size, move count and active elapsed time. On 3×3 it can also include the independently computable exact minimum. The specialist streak advances from the previous calendar date when the previous date is already in this specialist history.

This history is intentionally separate from the main Daily model. Completing Daily Sliding Puzzle does not add a game to Today’s 6, does not change a Today’s 6 score, and does not change the frozen twelve-game rotation source. A new specialist can therefore have a repeat-visit loop without breaking historical Daily archives.

Autosave and returning later

Every legal move updates a browser-local autosave. The saved state includes the exact tile order, move count, Undo history, elapsed active time and pause state. If a browser context is closed and the same date is reopened with that local storage intact, the app restores the board instead of generating a replacement.

Active timing pauses when the page is hidden. This matters for a daily puzzle because people often switch tabs, lock a device or return later. The timer is meant to measure active play, not how long the page happened to remain open in the background. A manual Pause button provides the same behavior on demand.

Touch, mouse and keyboard

On touch or mouse, you can tap the numbered tile immediately beside the gap. You can also tap farther down the same row or column; every intervening tile then slides toward the empty space in legal order. Each shifted tile still counts as one move, so the convenience control does not lower the reported move total.

Arrow keys and WASD move the gap one square for keyboard play. Ctrl/Cmd+Z restores the state before the previous input. P pauses or resumes. The 5×5 board is sized to fit a narrow phone viewport without horizontal page overflow, while the desktop version expands to a larger square instead of stretching the tiles into a wide rectangle.

How to approach a Daily board

Before moving, find the blank and inspect which completed rows or columns can be built without trapping the gap. On a 4×4 or 5×5 board, preserving finished layers usually matters more than moving one attractive tile directly toward its target. The final two tiles of a row often have to be prepared together so they can rotate into place without destroying the earlier part of that row.

Undo is useful for comparing two local branches. Because the Daily board is fixed for the date, you can also restart and try a different route from the same initial arrangement. On 3×3, the exact minimum offers a concrete efficiency challenge. On larger boards, your own previous attempts on the same mode are a more honest comparison than an unverified global “par.”

Local-first limits

The Daily streak, history and autosave stay on this browser. There is no account, cloud profile or cross-device synchronization in the public build. Clearing browser data can remove those records. This is an explicit tradeoff of the current local-first architecture rather than an invisible promise that progress has been uploaded somewhere.

The Daily result is also not a cognitive or medical assessment. Moves and active time describe only how this puzzle was played. The project does not convert them into IQ, percentile, attention, intelligence, diagnosis or health claims.