Bend gravity. Shape orbits. Trigger supernovas.
Explore a universe in motion — and see what happens when you disturb it.

_{Interactive WebGL experience · runs in your browser · no account or backend required · event-horizon-teal.vercel.app}

_{Captured from the live application. In The Hungry Singularity, matter is painted toward the accretion disc before a nearby supernova sends a shockwave through the scene.}

Event Horizon is an interactive cosmic physics sandbox built around one simple idea: give people the tools to disturb a universe, then let gravity tell the rest of the story.

Drop a black hole into a spiral galaxy. Redirect a stream of matter. Launch a planet into orbit or detonate a star. Watch particles scatter, objects interact, and discoveries emerge from the simulation.

This is more than a space-themed screensaver. The simulation advances on a fixed clock, independently of rendering, with reproducible starting worlds and tools to pause, rewind, undo, checkpoint, save, and revisit experiments. Its discovery system detects meaningful events as they happen, including stable orbits, event-horizon captures, merges, shockwaves, and gravitational slingshots.

The application currently displays the in-app title GOD MODE. Event Horizon is the public project name for that same application.

The Force Lab exposes the selected tool's parameters. Tune the gravitational constant and trail length to change how the universe behaves and how its motion is displayed.

Each world is a reproducible starting point generated from a fixed seed. Choose a setup, experiment, and return to the same initial conditions whenever you want.

The Hungry Singularity A black hole and its swirling accretion disc. Send matter inward and watch the encounter unfold.	Stellar Collapse A dense stellar environment poised for a dramatic release of energy.
Binary Dance Two stars in a mutual orbit, surrounded by drifting matter.	Total Chaos Singularities, stars, and a repulsor sharing one unpredictable field.

The atlas also includes Prime Field, a spiral galaxy with a binary companion and three planets, and Slingshot, a high-velocity encounter shaped by a massive star's gravity.

_{These are frames captured from the production application, cropped with the interface hidden. The wordmark above is decorative artwork.}

_{The full instrument: tool rail, Force Lab, discovery feed, simulation transport, rewind, and reset.}

• Control time. Pause and resume, change simulation speed, rewind through captured states, create checkpoints, and undo or redo experiments.
• Follow discoveries. Objectives and the live event feed surface detected events such as stable orbits, event-horizon captures, merges, shockwaves, and gravitational slingshots.
• Keep your experiments. Store up to eight local saves, rename them, export JSON, and import validated experiments. Saves remain in your browser.
• Hear the universe. Procedural audio responds to the simulation with ambient layers and event sounds. Mute it whenever you like.
• Choose your visual quality. Cinematic, Balanced, Performance, and adaptive Auto quality options tune rendering without changing the underlying particle simulation.

A small ringed creature lives in the bottom-left corner. Orbito watches the same events as the discovery feed: black holes you open, supernovas you detonate, stars that collapse on their own, mergers, bodies swallowed by a black hole, matter crossing a horizon, slingshots, discoveries, world changes, pause and resume. It reacts with one of ten expressions and, now and then, an opinion. It never repeats a line back to back, keeps quiet while you're paused, and goes to sleep if you leave it alone.

Click Orbito (or Tab to it and press Enter) to talk. Its answers come from the live universe: what's happening, why something was flung away, what doubling the selected body's mass would do, how black holes, mergers, orbits and shockwaves work here, and what to try next. The first time you pick each tool, it explains what that tool really does. When a question is beyond what the universe reports, it says so.

• Voice, optional and off by default. VOICE speaks through your browser's own speech engine, choosing the lightest, youngest-sounding voice available (Microsoft Ana in Edge, then natural or Google voices, Samantha on Apple devices, Zira on Windows) and steering away from deep narrator voices. It follows M mute and the volume slider, never talks over itself, and stops when you close the panel. Available voices depend on your browser and operating system.
• Quiet when you want. QUIET limits unprompted remarks to discoveries. Esc closes the conversation, H hides Orbito with the rest of the interface, and typing to Orbito never triggers simulation shortcuts.
• No network, no keys. Conversation runs on a local, deterministic engine. Orbito remembers only a few counters and its two settings, in your browser.

Event Horizon combines a deterministic simulation core with a real-time Three.js/WebGL renderer. The visual language is designed around the physics: a black hole's photon ring and limb-darkened photosphere, Doppler-shifted accretion-disc lighting, stellar diffraction spikes, additive particle trails, shockwaves, and a world-anchored graticule that scales as you navigate.

The engineering is just as deliberate:

• Fixed-step physics: a 1/60-second simulation step keeps physics independent of display frame rate.
• Stable numerical behavior: semi-implicit (symplectic) Euler integration and Newtonian gravity with Plummer softening; matter is additionally bounded in acceleration and speed. A circular orbit drifts by about 0.001% in energy over ten revolutions.
• Conservation where it counts: bodies pull on each other in equal and opposite pairs, mergers keep total momentum and land at the pair's centre of mass, and a black hole takes on the momentum of the matter it swallows. Each of these is covered by a regression test.
• Deterministic particle recycling: particle storage is bounded, with a 24,000-particle ceiling.
• Two-phase slingshot detection: a flyby is armed on inbound motion and counted only after outbound escape, avoiding false discoveries during scenario loading.
• Rendering-only quality tiers: visual quality changes do not trim or otherwise mutate the simulation's target particle population.
• Adaptive Auto quality: a measured P95 frame-time controller adjusts rendering quality with hysteresis and cooldown to avoid rapid oscillation.
• Event-driven effects: merges, captures, stellar collapse, supernova shockwaves, and other simulation events drive visual and audio feedback.

The black-hole and relativistic-looking effects are visual approximations layered over the simulation; this is an interactive sandbox, not a general-purpose relativistic astrophysics solver.

src/core/    physics, particles, worlds, scenarios, events, objectives, history, serialization
src/render/  Three.js renderer, shaders, camera
src/input/   pointer, mouse, and touch interactions
src/ui/      panels, controls, help, notifications
src/audio/   procedural Web Audio
src/orbito/  companion: brain (moods, reactions), knowledge (context, answers), voice, view
src/app.ts   application orchestration

Requires Node.js 20.19 or newer and npm.

npm ci
npm run dev

Open the local URL printed by Vite (normally http://localhost:5173).

Build and preview the production bundle:

npm run build
npm run preview

On touch devices, tap and drag to use tools, use two fingers to pan, and pinch to zoom. The panel toggle keeps controls reachable on smaller screens.

Accessibility and comfort. The application responds to prefers-reduced-motion, provides visible keyboard focus, and labels toolbar and transport controls for assistive technology. Sound can be muted with M or the volume control. The Performance and Auto quality options help adapt rendering to available hardware.

The release benchmark was measured on an RTX 3050 Laptop GPU (6 GB) using ANGLE over Vulkan, at 1280×800. The recorded final run reported:

These measurements were display-refresh-bound at 144 Hz; they do not establish maximum GPU throughput. The benchmark report documents the methodology, quality tiers, environment, and limitations. See docs/BENCHMARKS.md.

This release (Orbito, event feed and conservation fixes) recorded:

Typecheck and production build completed cleanly. The previous release's wider campaign (QA smoke 6/6, 10/10 seeded personas, 100/100 fuzz cases, 12/12 user acceptance checks, a 600.8-second extended session) was not rerun for this release.

Run the core checks locally:

npm run typecheck
npm test
npm run build
npm run preview            # then, in another terminal:
npm run smoke
node scripts/orbito-check.mjs                          # Chrome
ORBITO_BROWSER=firefox node scripts/orbito-check.mjs   # or webkit; needs `npx playwright-core install firefox webkit`

Event Horizon is a static Vite application. Use the Vite preset, npm ci for installation, npm run build as the build command, and dist as the output directory. No backend or environment variables are required.

Production: event-horizon-teal.vercel.app.

Bug reports and ideas are welcome through GitHub Issues. Before opening a pull request, describe the proposed change and run the relevant typecheck, test, and build commands. Include screenshots for visual changes and benchmark evidence for performance-sensitive changes.

Event Horizon is licensed under the MIT License. You may use, modify, and distribute the software under its terms; retain the copyright and license notice in copies or substantial portions of the software.

Enter the universe →