HTML and CSS Reference
All possible positions of the upper-left corner are matched in Figure 6-6 .
Figure 6-6. Five possible positions for the upper-left corner of the tile
Other corners will be drawn following the same principle, as shown in Figure 6-7 .
Figure 6-7. Surface symmetry
In the end, you have the variant shown in Figure 6-8 , where you can see that some corners are not used.