Constant MOAT_REACH 

pub const MOAT_REACH: i32 = _; // 6i32

How far outside its edges a block reaches into the lattice. The moat is seeded a lane at a time at distance + 2 cells out, so the outermost lane — and with it the last channel this block trims or creates — sits here.

Anything routing within this of a block is routing in a channel that block shaped, and so is geometry that block’s movement can change.