Lamp sight coverage
Light every open square while preventing any two lamps from seeing each other.
Logic & rule checking
- Players
- 1–3
- Time
- 15–25 minutes
- Materials
- Printed puzzle, pencil and separate host key
Prepare
Use the supplied 4×4 board, columns A–D and rows 1–4. Rows increase upward. B2 and C3 are walls, both labeled 1; all other cells are white. Work alone or let one partner propose lamps and another check their rays.
Follow the rule
Put lamps only on white cells. A lamp lights its own square and all white squares in its row and column until a wall or the board edge stops the ray. Light does not bend around a wall. Two lamps may never see one another along such a ray.
Check each step
Each numbered wall must have exactly that many lamps in its orthogonally adjacent cells. Diagonal lamps do not count. The digit is not the total number of illuminated neighbouring squares.
Worked example
Try A2,C1,B4,D3. Trace each ray and check both numbered walls. As a counterexample, adding D1 is illegal because D1 sees C1 along row 1 and D3 along column D.
Finish and adapt
Finish only when every white cell is lit, wall counts match and no lamp sees another. The key supplies one valid arrangement, not a uniqueness claim. Erase proposals rather than moving walls; a partner can dictate coordinates if writing is difficult.
Purpose, observation and provenance
Within this activity: Light every open square while preventing any two lamps from seeing each other.
Check each constraint independently rather than compare only with the sample answer.
Our rules, examples and printable diagrams are separately prepared. The earliest inventor of the broader mechanism is not established here.
Official mechanism reference / 官方机制规则 — Background rules only; all small boards, examples and explanatory text are prepared for this kit. No publisher artwork is reproduced.
Free alternative: Copy the supplied grids, labels and cards onto reused paper. No specialist product is needed. Adults may prepare pieces or act as a scribe.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Lamp sight coverage · Player sheet
Before you begin
- Use the supplied 4×4 board, columns A–D and rows 1–4. Rows increase upward. B2 and C3 are walls, both labeled 1; all other cells are white. Work alone or let one partner propose lamps and another check their rays.
- Put lamps only on white cells. A lamp lights its own square and all white squares in its row and column until a wall or the board edge stops the ray. Light does not bend around a wall. Two lamps may never see one another along such a ray.
- Each numbered wall must have exactly that many lamps in its orthogonally adjacent cells. Diagonal lamps do not count. The digit is not the total number of illuminated neighbouring squares.
| Proposed cells / boundaries | Constraint checked |
|---|---|
| ________ | ________ |
| ________ | ________ |
| ________ | ________ |
Lamp sight coverage · Host key — keep separate
A2,C1,B4,D3 lights all 14 white cells. B2 has A2; C3 has D3.
Read the rules as well as this example. Other valid solutions may exist for the puzzle boards. This key is not a claim of uniqueness or measured learning gains.
| Constraint / action | Evidence / correction |
|---|---|
| ________ | ________ |
| ________ | ________ |
| ________ | ________ |
| ________ | ________ |
Related activities
Activity library · Cross-toggle lights: rules and printable materials