Double Doku (803)

Other names: Duodoku

Instruction:

Place a number from 1-9 in each empty cell in the two overlapping grids such that each row, column and marked 3×3 box contains each number exactly once.

Reference: WPF (1)

Examples:

WPF Sudoku GP 2015 - Round 6 (109)

Parent puzzle:
Multi Sudoku