FIXED PRACTICE BOARD
Cross Lights study 3
Solve at your own pace. Ask what follows from the position before applying the suggested move.
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Loading interactive controls…
Work from the current board
Activate a square to toggle its cross. An explained plan is recalculated from your current pattern; it is one valid solution, without a minimum-move claim.
Tab to any control and use Enter or Space.
Interactive help is separate from the written starting-board solution below.
What did this solve teach?
You met the complete win condition. Compare the written route below with your own moves. Identify one deduction you can explain without looking at the answer, and one place where a changed mark could invalidate the next conclusion.
Rules and proof limits
Switch every light off. Pressing a square flips that square and its horizontal and vertical neighbours. Edges do not wrap and diagonals do not change. The fixed challenges stop when solved. The prediction drills describe toggle operations even when an intermediate pattern is dark.
Cancellation and order independence describe the toggle operations. The live game stops accepting moves when the board is solved, so a comparison that passes through a solved state belongs in a practice sandbox. Row chasing tests a chosen first-row pattern; it does not guarantee that an arbitrary choice works or produces the fewest moves. A solvable board can have more than one solution.
Show the checked route from the starting position (2 steps)
This route starts from the original study position. It does not describe moves you made differently. Use “Explain a next step” for a deduction from your current marks.
- Testing all 32 possible first-row patterns and chasing downward gives a valid plan from this exact position: R1C1, R5C5. Press R1C1 first; it toggles R1C1, R2C1, R1C2. This is one working plan, not a claim of fewest moves.
- Testing all 32 possible first-row patterns and chasing downward gives a valid plan from this exact position: R5C5. Press R5C5 first; it toggles R5C5, R4C5, R5C4. This is one working plan, not a claim of fewest moves.
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Final check
Applying the listed cross toggles leaves every cell off. This verifies a solution, not a minimum number of presses.