The basicsBasic boards
Full house
When a row, column or box has eight of its nine numbers, the empty square takes the one that's missing.
The row with one gap2The answer it gives
Rows, columns, boxes
The same check works on all 27 of the board's rows, columns and boxes.
How to spot one
Scan for a group that looks almost full. Boxes are the easiest to see, because their nine squares sit together.
What it gives you
A placed number, every time. Late in a board they come in runs: each one you fill can finish a group next to it.
Practise Full house
Boards that need it, with the owl's hints when you're stuck.