3D ENDLESS RUNNER FREE
Fern Valley Run
Swipe. Jump. Chase the amber.
A free 3D dinosaur runner you play right in your browser. Guide a little raptor through three valleys, dodge trees and pterosaurs, hop rocks and logs, and chain amber for a ×5 combo. No download, no signup.
PLAY IT RIGHT HERE
NO DOWNLOAD. JUST RUN.
STRAIGHT FROM THE GAME
TAKE A CLOSER LOOK.
HOW TO PLAY
A LITTLE KNOW-HOW. A LOT OF FUN.
Swipe to switch lanes
Swipe left or right to move between three lanes. On a computer, use the arrow keys or A and D.
Jump, drop and grab amber
Swipe up or tap to jump over rocks and fallen logs, swipe down to drop fast. Grab amber in a row to raise your multiplier up to ×5.
Reach the next valley
The run speeds up as you go. Sunset Ridge starts at 450 m and the Ember Fields at 1000 m, with pterosaurs and rolling boulders on the way.
HOW IT WAS MADE
BUILT WITH CLAUDE OPUS 5.5 IN AN AFTERNOON.
Fern Valley Run started as a test of how far Claude Opus 5.5 can take a 3D game from plain-language prompts. The answer: a complete, playable runner in one sitting, then a second pass for combos, power-ups and harder hazards.
One file, no images
About 800 lines of HTML and JavaScript with Three.js. The raptor, trees, mountains, gradient sky and lava cracks are all shapes and colors made in code.
Two prompts, two versions
The first prompt asked for a small 3D browser game. The second asked for more appeal and more challenge, which added three zones, a ×5 combo, near-miss points, a shield, a magnet and three new hazards.
Tested before it shipped
Each version was played in a real browser, with screenshots checked for every zone before it went live on this page.
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Is Fern Valley Run free?
Yes. It is free to play in any modern browser on a phone, tablet or computer, with no download, no account and no ads.
How do I play on a phone?
Hold your phone upright. Swipe left or right to change lanes, swipe up or tap to jump, and swipe down to drop back to the ground. Skim past a hazard in the next lane for +15 bonus points.
How was this game made?
Claude Opus 5.5 wrote the whole game from short prompts in one afternoon: a single HTML file using the Three.js 3D library. Every tree, mountain and dinosaur is built from code, so the game has no image files at all.
Will it come to the App Store?
A native iPhone and Android version is on our list. Join the studio newsletter on this page to hear when it is ready.
ONE MORE LITTLE ADVENTURE
