The Omega Sandbox: Excitable Engine Edition — an interactive FitzHugh–Nagumo visualization with a pluggable-engine architecture

The Omega Sandbox: Excitable Engine Edition is a single-file, browser-based interactive instrument that visualizes a small excitable dynamical system as an animated cosmic "core" reacting to stimulus. It builds directly on the Omega Sandbox by Matthew Arthur Carlo (DOI: 10.5281/zenodo.20848956), keeping its scene system, telemetry vocabulary, and engine-swap contract, and replacing its sealed demonstration engine with a FitzHugh–Nagumo (FHN) excitable unit — a textbook two-variable reduction of the Hodgkin–Huxley neuron model. The FHN core is extended with three slow state variables (an adaptation term, an allostatic-load variable, and a safety/extinction variable) that give it memory, so a single excitation becomes a richer arc: it spikes on input, accumulates load under sustained stress, stays elevated after a stressor is removed, and recovers slowly once the environment is quiet. The instrument adds interactive ways to drive the engine (a draggable core, an acute-shock control, a spawnable field of attracting/soothing bodies under mutual gravity, and scripted stimulus scenarios) and an extensive rendering layer (gravitational lensing, a black-hole collapse in overload, bloom, plasma arcs, shockwaves, gravitational-wave ripples, sonification, and a parallax camera). The original engine-swap architecture is preserved: any model satisfying the contract can drive the visuals, and a normalizer fills any fields a minimal engine doesn't provide. A Lorenz attractor is included as a worked example. This is a creative and educational visualization built on established dynamical-systems mathematics. It is not a research result or a novel finding, and it is not a model of consciousness, a brain, or any lived experience — the variable names ("arousal," "load," "safety") are analogies for the system's behaviour, not claims about it. The accompanying PDF documents the full model, parameters, architecture, controls, and engine-swap interface. This work is a derivative of the original Omega Sandbox and is published with attribution to it; please cite both.