PAPER PRACTICE
Cross Lights: Compare sequences by their effect
Three fixed studies, followed by separate answer pages. The links and IDs match the online collection.
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.
Use your browser’s Print command or Save as PDF. Both A4 and US Letter fit the diagrams. To keep answers separate, print only the challenge pages. The answer pages contain two useful checkpoints; the online practice page contains the complete checked route.
CHALLENGE 1
Cross Lights study 4
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Explain one move you can prove. Which displayed clue or rule supports it?
Reason: ____________________________________________________
___________________________________________________________
CHALLENGE 2
Cross Lights study 5
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Explain one move you can prove. Which displayed clue or rule supports it?
Reason: ____________________________________________________
___________________________________________________________
CHALLENGE 3
Cross Lights study 6
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Explain one move you can prove. Which displayed clue or rule supports it?
Reason: ____________________________________________________
___________________________________________________________
ANSWER 1
Cross Lights study 4
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Two checkpoints in the solution
- Testing all 32 possible first-row patterns and chasing downward gives a valid plan from this exact position: R1C2, R2C3, R4C5. Press R1C2 first; it toggles R1C2, R2C2, R1C1, R1C3. 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: R2C3, R4C5. Press R2C3 first; it toggles R2C3, R1C3, R3C3, R2C2, R2C4. This is one working plan, not a claim of fewest moves.
ANSWER 2
Cross Lights study 5
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Two checkpoints in the solution
- Testing all 32 possible first-row patterns and chasing downward gives a valid plan from this exact position: R1C1, R2C2, R3C3, R4C4. 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: R2C2, R3C3, R4C4. Press R2C2 first; it toggles R2C2, R1C2, R3C2, R2C1, R2C3. This is one working plan, not a claim of fewest moves.
ANSWER 3
Cross Lights study 6
| C1 | C2 | C3 | C4 | C5 | |
|---|---|---|---|---|---|
| R1 | |||||
| R2 | |||||
| R3 | |||||
| R4 | |||||
| R5 |
Two checkpoints in the solution
- Testing all 32 possible first-row patterns and chasing downward gives a valid plan from this exact position: R1C3, R2C4, R3C5, R5C1, R5C5. Press R1C3 first; it toggles R1C3, R2C3, R1C2, R1C4. 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: R2C4, R3C5, R5C1, R5C5. Press R2C4 first; it toggles R2C4, R1C4, R3C4, R2C3, R2C5. This is one working plan, not a claim of fewest moves.