1fr 2fr
3fr 2fr
auto-flow 30px
[top] "a1 a1" 10px [mdl] "a2 a3" 30px [btm]
1fr 2fr 2fr 1fr
1fr 2fr 2fr 3fr
40px 80px 1fr
repeat(auto-fit, 140px)
[lft] 1fr [cnt] 2fr [rht]
grid-template-rows: 1fr 2fr
grid-template-columns: 1fr 2fr 2fr 1fr
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