KEEP IN MIND
- Count other blue tiles, not diagonal neighbors.
- Stop a ray at the first red tile.
- Combine all four directions for a clue.
- Check unnumbered blue tiles for a companion.
Trace four rays from a numbered tile
Start at the clue and look up, down, left and right. Count the visible other blue tiles until a red tile or the board edge stops each ray. Do not count diagonals or tiles hidden beyond a red blocker. Write the four small counts mentally before adding them, so a long horizontal line does not distract you from a short vertical one.
A met count restricts the open ends
If a clue already sees the required number of blue tiles, extending an open ray with another blue would exceed it. The next unresolved tile at that end may need to be red. Confirm that the entire four-direction count is complete first; satisfying one direction does not satisfy the clue by itself.
Too little available space can force blue
Consider the maximum number of visible tiles the remaining open directions could provide. If the clue still needs all of them, those positions cannot become early red blockers. This is a general deduction strategy based on the visibility rule. Recount after every forced tile because it may change the possibilities for a crossing clue.
Look for a blue tile with no companion
Each blue tile must see at least one other blue. A tile surrounded by red or edges in three directions has only one remaining way to connect. Check those isolated-looking positions even when they have no printed number. A board can satisfy nearby numbered clues while still leaving an unnumbered blue stranded.
Do not balance the colors
0h n0 does not use its companion’s equal-color or duplicate-row rules. Your check is whether each blue has a companion and each numbered clue has the right visible count. If you find yourself filling a row to make the colors equal, pause and return to the actual rule panel.
