Feryl

About This Game

Feryl is a tiny digital creature that lives in a terrarium on your desktop.

It isn’t animated or scripted — its behavior emerges from a continuous simulation driven by an internal rhythm.

You can watch it explore, speak to it through your microphone, or try to play games with it.

Overview

Feryl is a very small digital creature that lives in a glass terrarium on your desktop.

It is not animated or scripted. Feryl is an experimental digital life simulation.

Feryl runs on a stochastic internal rhythm — a forever-repeating breath cycle that is always unique and drives everything it does: where it looks, when it moves, what it pays attention to, how it reacts, and how it learns about the world around it.

You can watch Feryl explore its enclosure, try to engage it with games, or speak to it through your microphone and see how it responds.

Features

A Living Digital Creature

Feryl is less a traditional game and more a small system you share space with.

Feryl’s behavior emerges from an internal rhythm rather than scripted animations. Its movement, attention, and curiosity arise from a continuous simulation running beneath the surface.

The autonomous system that drives Feryl — perception, attention, speech, breathing, and behavior — fits in roughly 70 kilobytes.

A Terrarium World

Inside the enclosure are small objects, a friendly fly, busy beetles, and simple ways for you to interact.

You can observe Feryl interacting with its space and learn its relationship with everything inside: its vine, its couch, its rock, its mirror, and the sound of you speaking through the intercom.

Play Tic-Tac-Toe with Feryl

A tic-tac-toe board inside the terrarium allows you to try to play a game with Feryl.

Click the board to start a match. If Feryl becomes interested, it may approach the board and make its move. If you can keep its attention, you may even complete a full game.

Over time, Feryl gradually improves through reinforcement learning after each match.

Voice Interaction

Feryl can hear you through your microphone and may respond with sounds of its own.

Over time it adapts slightly to the vowel shapes and rhythms of the voices it hears.

Unique Creatures

Each Feryl begins from a seed, producing a creature with its own timing, tendencies, and behavior patterns.

Feryl states can also be exported as text codes, allowing you to preserve or share particular creatures and their environments.

A Quiet, Ambient Experience

Feryl is designed to exist alongside your desktop.

It doesn’t demand constant attention. Feryl lives in its terrarium. Whenever you have a moment, it’s there — even if it’s distracted.

AI Generated Content Disclosure

The developers describe how their game uses AI Generated Content like this:

AI-assisted tools were used during development to help create certain store assets and to assist with portions of the program’s source code.

The shipped game does not generate AI content during gameplay and does not connect to external AI services.

Visual effects and imagery in the game are generated deterministically by the program’s code using mathematical and procedural rendering techniques (ASCII graphics and SDL-based visual effects). These systems do not use generative AI.