What if: follow a cup until it breaks
On the hardest boards the simple steps run out. Then you imagine a cup on one spot and follow the easy steps from there. If a few steps later some row, column or table has no room left, that spot gets an X.
Before
After
How to spot it
- Pick a spot with big consequences: one next to a small table, or in a row with few free spots.
- Follow only the simple steps in your head: the crosses from that cup, then any last free spot that appears.
- Stop as soon as a row, column or table has nothing left. That proves the spot is wrong.
Why it works
A cup on that spot leads, by steps that cannot go any other way, to a row, column or table with no free spot. A puzzle with one solution never does that, so the cup was wrong and the spot gets an X. It is not a guess: you never keep the cup, you only use it to rule the spot out.
Try it on a real board
Play a free board in your browser, no account needed. When you are stuck, the hint shows where to look, then explains the step.
The Brewdoku app has 300 levels that bring in these steps one at a time, from small boards to 10x10, and a hint that shows where to look, then why, and only then makes the move.
