Overview
fill is route coverage distilled into straight swipes and parity, where the roller moves until it hits an edge and your sequence decides whether tiles clear elegantly. You anchor structure with long straights, reserve small islands for final sweeps, and avoid zigzags that leave stray cells. The trick is planning parity—opposite swipes meet to complete areas—and keeping pivots until edges are ready. The cadence becomes relaxing: long lane, short cap, pivot, finish. Misses are instructive: redundant passes say start lines were poor, leftover islands mean fill order was wrong, and messy corners suggest premature pivots. Correction is small: reset one start lane, replace a zigzag with two straights, and coverage tidies itself. It’s paint-by-geometry that rewards thinking one step ahead.