Home Ignition Zone — Wind-Driven Spread & Firebrand Ballistics (2D)

This top-down 2D companion to the Home Ignition Zone 3D simulator replaces the 3D scene's single shrinking radius with a genuinely spatial fire perimeter: 72 independent angular sectors each advance at a rate set by local fuel clearance and by how that sector's compass direction aligns with the wind, so a head fire pushed by the wind visibly outruns a backing fire crawling against it — real, well-documented wildfire behavior that a single uniform ring cannot show. Firebrands are individually integrated projectiles rather than a canned travel formula: each is launched from the upwind arc of the burning perimeter at a speed set by Byram's classical flame-length relation, then flown frame by frame under gravity, quadratic air drag that settles it to a realistic terminal fall speed, and wind-relaxed horizontal drift, so how far embers land ahead of the fire emerges from that physics instead of being read off a lookup table. Set each defensible-space ring's clearance and the Zone 0 toggle and watch how both the ground fire's approach and the ember-driven spot fires it seeds ahead of itself change the structure's live ignition probability.