Skyscrapers: rules and how to play

Goal of the game

Place building heights so that every row and column uses the required numbers and every edge clue sees exactly the stated number of buildings.

Rules

• On an N×N grid, use heights 1 through N once in each row and column. Keep any given heights.
• Look from an edge clue straight along its row or column. A building is visible only if it is taller than every building before it from that viewpoint.
• An edge clue counts visible buildings, not their total height. A blank edge supplies no clue.
• A taller building hides smaller ones behind it, but cannot hide an even taller building farther along.

A small example, step by step

1. Read the line 1, 3, 2, 4 from the left.
2. Height 1 is visible. Height 3 is taller than 1, so it is also visible.
3. Height 2 is hidden by 3. Height 4 rises above everything before it: the left clue is 3.
4. From the right, 4 hides all three others, so the right clue is 1. The direction changes the count.

Beginner deductions

• A clue of 1 puts N in the nearest cell. A clue of N forces 1, 2, …, N away from that edge.
• Combine those placements with missing numbers in crossing rows and columns.
• For other clues, list possible orders of the remaining heights and discard any that fail either edge clue. A value common to all surviving orders is forced.

Common mistakes

• Do not add the heights to read a clue.
• Do not count a shorter building hidden behind a taller one.
• Do not treat a blank edge as zero visible buildings, or read a right/bottom clue from the opposite side.

Controls and availability

Select a cell, then enter a digit using the keypad or keyboard. Draft records candidates. Undo, Clear cell and Clear all let you edit the grid. Check becomes available when the grid is filled. Test grids are available on DEV for Premium members; human difficulty calibration remains pending.

Difficulty

The intended difficulty contract is Easy, Medium and Hard solved entirely by logical deductions, with zero hypotheses. Hard may require longer chains or more demanding techniques. Expert may allow an explicit hypothesis, following its consequences and rejecting it if it contradicts a rule. A unique solution alone does not prove a logical solving path. Unclassified means not yet graded, not automatically Expert. Human calibration remains pending; these are requirements, not a claim that all bands are available.

FAQ

Do I need Premium to read this guide?

No. Reading the rules is public; playing the new game requires Premium.

Does a difficulty label guarantee a calibrated game?

Not during this preview. Human review is pending. The intended distinction is deductions only for Easy/Medium/Hard; hypotheses may be used in Expert.

What if I cannot find a move?

Recheck the rules and the last certain steps, then revisit the deductions above. Keep possibilities separate from confirmed answers; being stuck is not proof that guessing is necessary.