Hi there, I haven't seen any good posts explaining the tower sight bug, so I'm going to show it myself.
Warcraft II's sight radius is always measured from a sight center point (red square on the red tower).
Since a tower is 2x2 there's no exact middle point, the lower right corner is set as center of sight.
This causes the following: a tower sees 9 units to the right and below, but since there's a piece of tower above and left to it, it sees only 8 units!
This has the consequence that a tower will see another tower 9 units below it but won't see a tower 9 units above it.
This sight bug also applies to the Farm (2x2 units, sight 3 units) and the Hall (4x4 units, sight 5 units) but since the sight area of these are smaller, it does not make much difference.
