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.

Objective

You are a lone breacher from the Port Authority Breach Unit, dropped into Saltline Terminal (Berth 4) at 05:42. Three uplink relays keep the port's rogue security net alive:

Relay	Location
A	Yard
B	Shed
C	Quay

Walk up to a relay and hold E (or USE on a phone) to cut it. When all three are dark, the extraction boat waits at the quay ladder, south end. Reach it to finish. Running for the boat with relays still live just gets you "the boat will not wait under fire".

Each relay you cut makes the net angrier: after the first, "machines inbound"; after the second, "it is throwing everything it has left at you". Top up ammo and health before you cut relay two and three.

Enemies

	Gull (drone)	Hound (robot dog)
Health	45	140
Attack	3-shot bolt bursts	4-shot bursts, plus a lunge at close range
Warning before firing	0.55 s	0.5 s
Preferred range	12–25 m, 4–8 m up	8–18 m
Notes	Explodes when destroyed (30 damage within 3 m)	Head is a weak point; smokes when badly hurt

• Your rifle (KR-7) hits for 28 per shot and holds 30 rounds with 120 in reserve. Weak-point hits do 2.2× damage.
• A Gull dies to two body hits. Don't finish one directly overhead or next to you: the wreck explodes.
• A Hound takes five body hits but only three head hits. If it gets within about 3 m it lunges for 15 damage, so back-pedal while you shoot.
• Both enemies flash a short telegraph before every burst. That half second is your cue to step behind steel.

Survival tips

• Health starts regenerating 4 seconds after you last took damage. "You are hit hard. Get behind steel and breathe" means exactly that.
• Container lanes break a Gull's line of sight quickly; Hounds follow you into the lanes, so fight them in the open where you can see them coming.
• Sprint (Shift) is almost twice walking speed. Crouch (C) moves at half walking speed. Aim (right mouse) narrows the field of view for long shots.
• Reload (R) in cover. You can melee with F or V.

Rating

The debrief grades the run from Messy, Loud, Steady and Clean up to Sharp and Surgical. The score adds up:

• Time: under 4:30 = 2 points, under 6:40 = 1 point
• Accuracy: 50% or better = 2 points, 30% or better = 1 point
• No retries: 1 point

Surgical (5 points) means a fast, accurate run with no deaths.

Controls

Action	Keyboard / mouse	Touch	Gamepad
Move	WASD	Left thumb, anywhere	Left stick
Look	Mouse	Drag the right side	Right stick
Fire	Left button	Hold FIRE (drag to track)	RT
Aim	Right button	AIM toggles	LT
Cut relay	Hold E	Hold USE at a relay	Y
Jump / Crouch / Sprint	Space / C / Shift	JUMP / – / push stick fully forward	A / B / L3
Reload / Pause	R / Esc or P	RLD / –	X / Start

If the browser won't capture the mouse, hold a mouse button and drag to look; arrow keys or IJKL also turn.