Slant / Gokigen Naname
Why is Slant wrong when every number matches?
Each numbered point needs exactly that many diagonal endpoints, but the lines must also contain no closed loop. Every cell needs one diagonal. A loop can be invalid even when its corner counts all match.
Worked example
After checking the numbers, trace connected diagonals until they end. Returning to the starting point reveals a forbidden loop.
What to check on your board
Apply the rule above to your current board, then verify the remaining puzzle constraints. The example explains a local deduction; it is not a solution to every randomly generated board.
Checking your next move
Count diagonal endpoints at each numbered point, then trace the connected lines independently of those counts. Mark a path mentally as you follow it; returning to a visited point closes a forbidden loop. Also check that no cell remains without its diagonal.
Using this reference
For Slant / Gokigen Naname, read the rule and the worked example together before opening the game. Separate what the rule explicitly requires from what only seems likely on the current board. A useful next move is one you can explain from the visible constraints, not merely a pattern that looks familiar.
If you get stuck, isolate a smaller part of the position and list what is still possible there. After a move, check the affected rows, regions or connections again. The reference explains the documented rules; progress, controls and save behavior belong to the linked game.
Read the developer’s manual ↗ · Open the developer’s browser version ↗
Manual inspected: · Simon Tatham & contributors · MIT