Picture sudoku · the one rule
One of
each
in every row.
🦉
🐱
🐻
🐸
🐻
🐸
🦉
🐱
🐱
🦉
🐸
🐻
🐸
🐻
🐱
🦉
The one rule
↔
Each row has one of each animal — no repeats
↕
Each column has one of each — no repeats
⊞
Each little box has one of each — no repeats