The morphing block
A block of parametric urbanism: one parameter turns a courtyard block into a block with one or two towers, so that neighbouring blocks can differ by degrees.
The rules it illustrates
From courtyard block to tower by degrees. Make the building types a continuum governed by parameters: let the perimeter block morph by gradual steps into a block with a tower, and into towers alone, so that neighbouring blocks differ by degree, never by collage.