Segmented spine, dual Hox programs, radial symmetry, digit gradients.
How it works: The body has a trunk (spine) repeated across segments. Two bud programs grow from branch-tips: Bud A (orange) on the anterior half of segments and Bud B (purple) on the posterior half — like Hox genes expressing different structures along the body axis. budSwitch controls the A/B boundary. trunkGrad tapers the spine across segments. budDensity controls what fraction of branch-tips actually sprout buds. radialArms repeats the whole organism rotationally (starfish, jellyfish). budGrad is a Sonic Hedgehog-like gradient that varies bud size across branch positions — left buds smaller or larger than right, creating asymmetric digits (thumb vs pinky). 36 genes total.