Halcyon
Halcyon
Play on halcyon.billpwchan.art ↗Opens on halcyon.billpwchan.art in a new tab. Check the setup notes below before starting.
About Halcyon
Walk, swim, sail and fly around a tropical atoll from sunrise to a glowing night sea.
Less a game than a place. A tropical atoll runs through a 36-minute day with weather that changes on its own. Start on the pier, then walk the beach, swim the reef, sail the lagoon, fly over the 330 m peak or sit back in tour mode.
There is no score. You skip or pause time, take photos, and wait for night, when the surf and boat wakes glow with bioluminescence. Whales, dolphins, turtles, mantas and reef sharks share the water.
How Halcyon was made with AI
From the README: 'Built with Claude Code running Claude Opus 5.5. I set the direction and reviewed every pass from screenshots and real-GPU frame timings; the model wrote the code, the shaders and the asset pipelines.' Same creator as Neon Zenith. Halcyon runs on WebGL2.
Made by Bill Chan (billpwchan).
How to play
Press Play on halcyon.billpwchan.art to open the project in a new tab, where it manages its own game files and browser permissions. It supports touch controls on phones and tablets.
| 1–5 | Walk, swim, sail, fly, tour |
|---|---|
| WASD / arrows | Move |
| Drag | Look |
| Shift | Faster |
| Space / C | Rise / sink |
| [ / ] | Half an hour back / forward |
| T | Pause time |
| H | Photo mode |
Quick facts
- Mountain built from USGS lidar of Ōlomana, O‘ahu
- About 43,000 plants and 370,000 coral colonies
- Open source, MIT
- Lighter asset tier on phones
Questions about Halcyon
Is Halcyon a game with a score?
No. It is less a game than a place: a tropical atoll running through a 36-minute day with weather that changes on its own. There is no score; you skip or pause time, take photos, and wait for night.
What can you do there?
Start on the pier, then walk the beach, swim the reef, sail the lagoon, fly over the 330 m peak or sit back in tour mode. Keys 1–5 switch walk, swim, sail, fly and tour.
Why is the water special at night?
At night the surf and boat wakes glow with bioluminescence. Whales, dolphins, turtles, mantas and reef sharks share the water.
Is it based on a real place?
The mountain is built from USGS lidar of Ōlomana, O‘ahu, with about 43,000 plants and 370,000 coral colonies. It is open source under MIT.
Tips for Halcyon
- Stay for the full day cycle at least once: the bioluminescent night surf is the payoff.
- Press H for photo mode, and use the [ / ] keys to scrub time to the light you want.
- Phones get a lighter asset tier, so it runs better on mobile than most 3D browser experiences.
Sources: github.com. Last checked .
