Each row, column, and 9-cell region must contain the digits 1 to 9 once each. Each main diagonal (marked in blue) cannot contain a repeated digit. Along thermometers, digits must increase from the bulb end.
Each row, column, and 9-cell region must contain the digits 1 to 9 once each. Each main diagonal (marked in blue) cannot contain a repeated digit. Along thermometers, digits must increase from the bulb end.