Think of the board as a grid. You need to iterate over each row, and within each row, over each column.
When you run the code, you should see:
# Move to the next column position pen.forward(square_size) 9.1.7 Checkerboard V2 Codehs
import turtle
: Instead of checking just the column index, we look at the sum of the row and col indices. If (row + col) % 2 == 0 , color the square red . Otherwise, color it black . Think of the board as a grid