Symmetry: Left and right sides the same
Size: 144 cells
Theme:
Answers were assigned to the left and right sides so as to generate 18 clashes,
which were resolved to reveal “greenfield site” on the left and “brownfield site” on the right.
Ambiguity in the bottom row was resolved to place
“horses” on the greenfield site (below “stable” in the top row)
and “houses” on the brownfield site (below “blocks”).