CSS Grid: grid gutters and tracks.

XX

XX
X
XX XX

XX

XX
XX XX

XXXX XX
X
XX XX

XX

XX
XX XX

XXXX XX
X
XX XX

X X X

X X

XXX XX X XX XX

X X X

X XX X XX XX XX X

X X

XX

X X
X X

XXX XX
X
XX XX

XX

X X
X X

XXX XX
X
XX XX

XXXXX

X

X

XXXX X XXXX

X XX X XX X

XXX XX
XX
XXXXX