Each starfish steers toward a chemical scent marker scattered on the reef floor. Its heading blends two terms every frame: a direct pull toward the current target, and a wander term whose amplitude falls as chemoreception rises — a starfish with strong chemoreception locks onto the plume and takes a near-straight line; a weak one wanders and takes longer to arrive.
Rocks scattered by the reef complexity slider are steered around (an inverse-square repulsion term) and drain energy faster the more of them a starfish must skirt. Energy depletes continuously and is topped up on contact with a marker, which also increments that marker's visit count (shown as a brightening glow) and the "patches explored" tally. A starfish that runs out of energy visibly slows and dims until it reaches its next marker.
- Glowing rings — chemical markers; brightness and ring size grow with visit count.
- Dark blobs — reef rock obstacles the starfish steer around.
- Star tint — warmer/brighter at high energy, pale grey near zero energy.