Full Visibility Clue
A clue equal to the grid size means every building is taller than the last — the whole line is forced into one exact order.
How it works
- 1The 4 on the top edge says all four buildings are visible down that column — every one must be taller than the last.
- 2Only one order does that: 1, 2, 3, 4 from the clue inward.
- 3The whole line is forced in a single stroke, starting with the 1 at the top.
- Relationship — The arrow shows which cells support the deduction.
- Conclusion — The final arrow lands beside the proved or ruled-out height.