This contest is part of 2021 World Sudoku + Puzzle Convention. Details here.
The official period for "03 - Great Wall of Sudoku" is over. However, you can participate unofficially using this link.
Your timer will start when you click "Start 03 - Great Wall of Sudoku" — then you will have 60 minutes to solve and submit your answers.
A timer will be shown the answer page with the remaining time.
If you have any questions or doubts or suggestions, please ask in the forum.