Saltline

Saltline is the game that kicked off the one-prompt FPS wave. It is one level in a rain-soaked container port: cut three uplink relays while drones ("Gulls") and robot dogs ("Hounds") hunt you.

How it was built

According to Felix Rieseberg's post, Claude Fable 5.2 built it from one prompt with no human feedback. The run took about 8 hours of autonomous work and consumed roughly 2.7M output tokens and 445M input tokens, most of them served from cache, which comes to about $550 at API pricing. The model planned the architecture, wrote the game, tested it with its own tooling and kept iterating.

How it works

The result is a single HTML file of about 1.4 MB. Models, sounds and textures are all made in code:

• Geometry: containers, gantry cranes and the quay are procedural Three.js meshes rather than downloaded .glb models
• Materials: corrugated steel, rust, wet concrete and signage are procedural textures generated at load time
• Audio: rain, weapons and enemy motors are synthesized with the Web Audio API, so there are no .mp3 or .wav files
• Enemies: two enemy types with distinct behaviour, airborne Gulls and ground-based Hounds

Because nothing is loaded from the network, the same file runs offline straight from disk, which made Saltline the reference point for every reproduction that followed, including SUBLEVEL 07, 盐线行动 Online and 几猫CS.

Controls & tips

• WASD move, mouse aim, click fire, ESC releases the mouse
• Click the game once to capture the mouse and start the audio
• Use the container stacks to break line of sight with Gulls; keep moving when Hounds close in

Credits

Run set up by Felix Rieseberg; the original artifact is on claude.ai. Played here through the realcodebear mirror, which only removes the claude.ai runtime scripts and adds a doctype, charset and viewport tag.