This is the flat, top-down companion to the 3D bioluminescent plankton simulator. Thousands of dinoflagellates float on a dark water surface and stay dark until something disturbs the water around them — a dragging cursor, a passing fish, or the ambient ripple of the sea itself — at which point they flash blue-green and slowly fade, just as real dinoflagellates use a mechanically-triggered luciferin-luciferase reaction as a startle defense. Drag through the water to paint a glowing trail, or watch the auto-swimming fish stir its own wake, and adjust density, sensitivity, decay and disturbance radius to see how the bloom responds.