I'm a bit confused by level six. grid-column-start: 0 - doesn't exist grid-column-start: 1 - leftmost square grid-column-start: 2 - 2nd square left to right gr

I'm a bit confused by level six. grid-column-start: 0 - doesn't exist grid-column-start: 1 - leftmost square grid-column-start: 2 - 2nd square left to right grid-column-start: -1 - also doesn't exist? grid-column-start: -2 - rightmost square Very strange. Although the concepts are neat so far. The / notation in grid-column: 2 / 4; is interesting. I'm surprised it's not similar to say margin: 20 30 20 20; where there's no slash, just an ordering to remember (clockwise from top). Default span is 1 which is sensible so grid-column: 3 === grid-column: 3/4 === grid-column: 3/span 1; Wow the fr unit is pretty neat! You can see where the slash is very useful in grid-template which makes a lot sense for dynamic numbers of rows and columns. Very fun. I still have some questions about the numbering, but a great way to learn about CSS grid and have a bit of fun.