1. Get to analyze the task’s description.
2. Download the file and take a look at a chessboard with highlighted places on it.
3. We can see that the white pieces are at the top of the board and move first.
4. We understand that the highlighted places are the base mate in chess, reproduce (see the screenshot) https://ibb.co/FqrZtBn

Flag: VishwaCTF{f3_e6_g4_Qh4#}.