How it's calculated
r = d ÷ 2; a block is filled when √(Δx² + Δy²) ≤ r
d = diameter in blocks, r = radius, Δx, Δy = a block centre offset from the circle centre. A filled disc keeps every cell inside r; a hollow ring keeps only inside cells that touch an outside cell. Area = πr², circumference = 2πr.
Common questions
How does the generator make circles look round in a grid?
It uses Bresenham's midpoint circle algorithm to choose which square blocks best approximate the curve at each step.
What is the difference between filled and hollow?
Filled fills the whole disk with blocks, while hollow only draws the outer ring, which is handy for towers and walls.