解释：row = ((row & 0x00FF) << 8) | ((row & 0xFF00) >> 8);

+ 1) % len(grid)) if the current row is not the last row in the grid, otherwise it becomes the first row.

This code is using the modulo operator (%) to check if the current row is the last row in the grid. If it is not the last row, then it adds 1 to the row number and assigns the result to row. If it is the last row, then it assigns 0 (the first row) to row.

This code is useful when iterating through a 2-dimensional grid in a loop and you want to cycle through the rows. It ensures that the loop will continue from the first row after reaching the last row.