Normal sudoku rules apply. The grid is covered with fog, except for two initial light sources. Digits also act as light sources and, when placed correctly, illuminate the cells around them. Cages show their sums, and digits cannot repeat within a cage. Digits on arrows sum to the single-digit number in the connected circle, and can repeat if allowed by other rules. Along green lines, digits must differ from their neighbours by at least 5. Digits in cells with a grey square must be even. Digits in cells separated by a black dot have a 1:2 ratio.