For a 5×4 Minesweeper grid (X=5, Y=4), build a DataFrame with columns 'x' and 'y' containing every coordinate, ordered (0,0), (0,1), (0,2), (0,3), (1,0), ….

Output

    x  y
0   0  0
1   0  1
2   0  2
3   0  3
4   1  0
.. .. ..
15  3  3
16  4  0
17  4  1
18  4  2
19  4  3

[20 rows x 2 columns]