Breathing Lungs
Twin lungs inflate and deflate along a branching bronchial tree, with airflow particles moving in and out. The bronchial tree is generated by recursively splitting each airway into two narrower daughter branches, echoing real lung anatomy where the trachea divides roughly 23 times down to microscopic alveoli.

• Recursive branching to depth 6, radius shrinking 0.72x per generation
• Lung lobes are noise-deformed icosahedron blobs, scaling with breath
• Sinusoidal breath cycle: smooth inhale/exhale, default 4.2s per cycle
• 220 airflow particles reverse direction between inhale and exhale