The shortest solution to this fixed 4×4 Lights Out puzzle is exactly five presses, a figure produced by an independent GF(2) oracle that enumerated all 65,536 possible press masks against the disclosed starting pattern. Pressing any tile toggles that tile together with its immediate up, down, left, and right neighbors that lie inside the board, while diagonal tiles never change. The starting board lights six cells, indexed from zero across each row at positions 1, 2, 3, 5, 9, and 10, and the all-off objective is to clear every one of the 16 lights. Because pressing the same cell twice restores its prior light pattern, only the parity of presses at each cell affects the final board, which is why the verified optimum has odd press parity at each of its five cells. The unique shortest path presses zero-indexed cells 0, 1, 3, 5, and 6 once each, the runtime tracks any press order that satisfies the all-off condition, and a successful check after the five-move boundary awards exactly 1,000 points.
What Makes a Lights Out Puzzle Easy
A puzzle is easy when its rules are simple, its starting state is fixed, and a known solution exists. This 4×4 Lights Out board meets all three conditions. The toggle rule is the standard cross rule described by GNOME's Lights Off help and by the UC Berkeley GamesCrafters reference: a press flips the selected cell plus its orthogonal in-bounds neighbors. The starting pattern is locked, with six cells on and ten cells off, and the solution is not a personal guess but a verified result. An independent test enumerates the full press space and reports rank 12, nullity 4, exactly 4,096 reachable effect states, and 16 distinct all-off press masks. Only one of those masks has weight 5, so the shortest path is unique. Beginners can play the fixture once, watch the cross preview, and finish in five deliberate presses, with no timing pressure, no random level, and no advance planning required beyond parity.
The Cross-Toggle Rule on a 4×4 Board
Every cell on the board is either on or off, and a single press reverses the state of the pressed cell and the states of its immediate up, down, left, and right neighbors that fit inside the 4×4 rectangle. Diagonals do not change, so a corner press flips three cells, a non-corner edge press flips four, and an interior press flips five. The currently selected tile carries a visible outline; its legal neighbors receive a lighter border preview so the upcoming toggle pattern is clear before the press is committed. That preview never changes any state by hovering and is purely explanatory. Each cell exposes its row, column, on-or-off state, and selection state in an accessible label, and the words On and Off plus surface contrast communicate state without relying on color alone.
GNOME's Lights Off basics page describes the selected-plus-non-diagonal-neighbor behavior, and UC Berkeley GamesCrafters' Lights Out entry independently confirms both the orthogonal toggle rule and the all-off goal that this edition follows.
Solve the Board in Five Presses
The verified five-move solution presses zero-indexed cells 0, 1, 3, 5, and 6 in any order. Because press order does not affect the final parity state, the steps below use the row-major order published for auditability. Open the Lights Out tool and follow the steps in order.
- Confirm the starting six lights match the fixed fixture at cells 1, 2, 3, 5, 9, and 10 before pressing anything.
- Use the arrow keys or your pointer to select cell 0, the top-left corner, then press Space, tap the cell, or click the Press selected button to flip that cell together with its three legal neighbors (0, 1, 4).
- Move to cell 1 with the right arrow and press it. Its four-cell cross covers 0, 1, 2, and 5, toggling each so the board advances toward the all-off target.
- Move to cell 3 and press it. Cell 3 is a corner that affects 2, 3, and 7, toggling each so the board advances toward the all-off target.
- Move to cell 5 and press it. This interior press flips five cells (1, 4, 5, 6, and 9), pushing the board into the lower half.
- Move to cell 6 and press it. Cell 6 affects 2, 5, 6, 7, and 10, completing the all-off pattern.
- Press Check or press Enter. With all 16 lights off and five or more moves recorded, the run scores exactly 1,000 points.
Press Geometries at a Glance
The 4×4 board contains three geometric press types. The table below lists each cell class, the count of tiles that flip, and a verified example taken from the production test cases.
| Cell type | Tiles affected | Verified example | Cells flipped |
|---|---|---|---|
| Corner | 3 | Cell 0 | 0, 1, 4 |
| Non-corner edge | 4 | Cell 1 | 0, 1, 2, 5 |
| Interior | 5 | Cell 5 | 1, 4, 5, 6, 9 |
These three counts come directly from the same goldens that verify double-press cancellation, initial-state fidelity, and the full mask-space enumeration. The five-press optimum uses one edge cell (1), two interior cells (5 and 6), and two corner cells (0 and 3). Those counts sum to 3 + 4 + 3 + 5 + 5 = 20 tile flips across the entire run, a verifiable side product of the cross-toggle geometry.
Check, Score, and the Repair Path
A check is only meaningful at or beyond the proven five-move lower bound. The game treats moves zero through four as objectively incomplete and records no mistake on a check during that window. At five or more moves, an all-off board succeeds, while any remaining light means the submitted path is complete but incorrect. The first such wrong check records one mistake and leaves the run editable, so the player can keep pressing tiles, reach all off, and check successfully. A second wrong complete check deadlocks the run until Restart, and Restart restores the exact six-light initial pattern, the cell-zero cursor, zero moves, zero mistakes, and zero score.
Completion and deadlock are terminal states. After either one, clicks, Space presses, cursor movement, selection changes, and further checks cannot modify the board. These guarantees live in the pure state-transition functions and are covered by tests, rather than depending only on disabled visual controls. A successful check awards exactly 1,000 points regardless of speed, extra moves, device, or input method; correctness is the only scoring predicate.
Why This Five-Move Answer Is Verified, Not Assumed
The five-move figure is not a hand-crafted hint. A separate GF(2) test, which does not call the production neighbor or press functions, builds one 16-bit effect column per board cell, performs binary Gaussian elimination to find matrix rank 12 and nullity 4, enumerates all 65,536 press masks, and counts 4,096 reachable effect states. Against the disclosed initial mask, the test finds 16 all-off solutions with Hamming weights 5, 7, 9, or 11. Exactly one mask has weight 5, so the shortest solution is unique, and applying its five effect columns to the starting mask yields zero. No mask of weight zero through four produces zero, which proves that this fixture cannot be solved in fewer than five presses.
The runtime game does not compare a move list against a hidden answer. It stores the 16 current light booleans, a press computes the selected cell's in-bounds orthogonal cross and flips those booleans, and a check accepts any 16-cell all-off state after the proven minimum boundary. This means longer valid solutions remain valid, as standard toggle algebra requires. Pressing the same cell twice restores the prior light pattern, and press order does not affect the final parity state even though the displayed move count records every physical press.
Other guarantees tested include double-press cancellation, initial-state fidelity, full mask-space size, rank, reachable-state count, total solution count, minimum weight, unique optimum, incomplete checking, repair after the first wrong complete path, exact scoring, second-error deadlock, terminal freezing, cursor boundaries, and deterministic Restart.
Practical Play Notes
Use the affected-cross preview while planning. Each selected tile shows the lighter border around the cells that the next press will flip, which lets a beginner reason row by row without writing anything down. Work from a corner first, since corner presses are the smallest cross and leave the most cells untouched. Avoid pressing the same cell twice in a row, because it always cancels, so even moves add no progress and can only push you closer to the second-error deadlock. Use Restart freely; it is the only way out of a second-error deadlock and it returns the board to the exact published state.
Everything runs locally in the browser. No board state is uploaded, no account is required, no random level is requested, no timer affects the result, and no new package dependency is introduced. The square four-column grid, concise status row, large native buttons, and wrapping controls are designed to fit a 390-pixel viewport without horizontal scrolling. If you specifically want to confirm the runtime behavior in a browser-only setting, the in-browser Lights Out guide covers the same rules from a download-free angle.
This is a recreational fixed puzzle, not an intelligence test, cognitive or medical assessment, educational placement tool, or employment screen. Repeated play naturally becomes easier through memory, which is why the score is based purely on correctness rather than speed.