ASHFALL

A small browser first-person shooter set in an abandoned city at dusk. Operation ASHFALL: twelve waves in the ruins of Carrow, then as long as you can last.

No build step, no asset files, no network calls — open the page and play. (The only files the page links are its tab and home-screen icons.)

Running it

npm start          # serves the repo at http://localhost:8000

npm start needs no dependencies — it runs a small static server from tests/serve.js. Any static server works just as well; the game only needs HTTP rather than a file:// path, because it loads ES modules. Three.js is vendored in vendor/, so it runs fully offline.

Add ?seed=12345 to the URL to replay an exact city; the seed for the current one is printed under the menu.

The world is built in the browser on every load — every texture is painted, the city laid out and the shaders compiled — which takes a few seconds. The loading screen says which part it is on, with a field note to read, and draws a survey of the sector as it goes: the street grid first, then the buildings and the rooftops a marksman can take once the city is laid out, and where you go in. The survey stays beside DEPLOY afterwards, so you can see the sector before you drop into it.

Branding

The logo, the icons and the X avatar and banner (@AshfallTheGame) are in assets/branding/, each as an SVG and a PNG. source/gen.mjs draws every SVG from code and the Rajdhani font beside it; source/render.cjs and source/render-icons.cjs render the PNGs with Playwright. favicon.svg is the avatar cropped to its ring with heavier strokes, so it still reads at 16 px, and the same SVG is inlined in index.html so the one-file build keeps its tab icon.

One-file build

npm run build      # writes dist/ashfall.html

That inlines the markup, CSS, all modules and Three.js into a single ~620 KB HTML file with no external references. It runs straight from a file:// path or from anywhere that can host one static file — useful for sharing a playable copy without the repo.

Testing

npm install        # playwright + esbuild, only needed for tests and builds
npx playwright install chromium
npm test           # the whole suite, headless

The suite drives the real game in a headless browser through window.__game, stepping the loop at a fixed timestep instead of waiting on frames — a four-minute simulated run finishes in seconds and does not depend on render speed, which matters because software WebGL renders at a couple of frames a second.

Flag	Effect
--seed=N	Replay an exact city (default is pinned, so runs are repeatable)
--only=text	Run only the checks whose name contains text
--shard=i/n	Run the ith of n slices of the suite, dealt by each check's weight — CI runs six side by side
--headed	Watch it play
--shots	Also write screenshots to tests/shots/

It covers boot and city generation, hit registration and headshots, melee reach, grenade flight and blast falloff, cook-offs, stair climbing, mantling onto ledges (and not onto walls), fall damage, marksman perching and laser tracking, warlord spawns, the objective schedule and its payouts, objective decay and expiry, waypoint projection, the texel density of every baked surface, the lane paint lying on the carriageway and facing the sky, the ambient darkening baked under the city, the view model being solid and unwrapped at its own scale, the route field covering the whole sector, a hostile walking around a building rather than into it, a turned prop stopping you where you can see it, the ground you stand on being the ground you can see, the best-score line sitting clear of the deploy button, ambient occlusion darkening contact and leaving open ground alone, the sun reading its near shadow map in the right light order, the sky and fog agreeing about where the sun is, aiming without pointer lock, settings and record persistence, every archetype being kitted and keeping its hit zones, nothing in the city or on a hostile being wound inside out, three seeds laying out exactly the cities they laid out before, and a four-minute scripted run that must reach wave 3 with hostiles still able to engage.

Three things make it trustworthy rather than merely green: the random stream is seeded, every check reloads the page so none of them inherit another's state, and the render loop is stopped during checks — otherwise it steps the game on real frame timing underneath the test and results stop repeating.

On every push

GitHub Actions runs the same suite, plus the one-file build, on every push to main and every pull request. The built ashfall.html is attached to the run as an artifact, so a change can be played from the Actions tab without checking the branch out.

Asking the game questions

When something looks wrong, measure it rather than guessing:

node tests/probe.js world                       # city stats for this seed
node tests/probe.js enemies                     # every hostile's AI state
node tests/probe.js objectives                  # where each objective lands
node tests/probe.js shot                        # what a bullet actually hits
node tests/probe.js perches                     # height profiles through each perch
node tests/probe.js --seed=777 "g.startRun(); __step(45); return __enemies()"
node tests/probe.js --list                      # the canned ones

It boots the game seeded and frozen, evaluates the expression inside it, and prints JSON. In scope: g (the whole game), __step(seconds), __enemies(), __profile(x, z, axis), __place(range). --file=path.js runs a longer probe from disk.

Every bug in this project has been found by looking at real state, and each time the first move was writing a throwaway script to get at it. This is that script, kept. It found a latent one within a minute of existing: hostiles spawned before the first wave got NaN health, because the per-wave health scale had no initial value.

Controls

Input	Action
W A S D	Move
Shift	Sprint (drops when you fire or aim)
Ctrl / C	Crouch — tighter spread. Out of a sprint, a slide
Space	Jump — held against a ledge, mantle onto it (~1.8 m from the ground, ~2.6 m off a jump)
Left mouse	Fire
Right mouse	Aim down sights
R	Reload
1–4, Q (tap), mouse wheel	Switch weapons
Q / E (hold)	Lean left / right round a corner
G	Frag grenade — hold to cook, release to throw
F / V	Melee bash
E (tap)	Open or close a door in front of you
B	Armoury — between waves, with the sector clear
M	Mute
`	Frame-rate readout
Esc	Pause

Click the canvas to capture the mouse — with pointer lock held, the cursor physically cannot leave the window, and losing it pauses the game. The clock stops while paused, so nothing — an objective, the gap before the next wave — runs out behind the pause screen.

Some contexts refuse pointer lock, most commonly a cross-origin <iframe> without allow="pointer-lock". The game detects that and switches to cursor steering: the pointer's offset from the centre of the screen becomes a turn rate, with a dead zone in the middle. That keeps working at the very edge of the window and stops cleanly if the cursor leaves it, where raw mouse deltas would simply die. A banner says which mode you are in, and offers to open the page in its own tab, where capture works.

Weapons

Slot	Weapon	Behaviour
1	M9 sidearm	Semi-auto, high headshot multiplier, always available
2	MP5K SMG	880 rpm, wide spread, best inside a room
3	M4A1 carbine	Recovered on wave 2 — the reliable mid-range answer
4	M1014 breacher	Recovered on wave 3 — nine pellets, heavy damage falloff

Every weapon has its own recoil pattern, spread (which tightens when you aim or crouch and opens when you move), reload timing and ADS zoom. Headshots do extra damage and are called out in the killfeed; limb hits do less.

An empty magazine reloads when you pull the trigger. A weapon with an empty reserve behind it has nothing left to reload from, so the trigger reaches for the next weapon that can still shoot instead of clicking at nothing.

You also carry frags (three to start, five max, dropped by kills). The fuse starts the moment you pull the pin, not when the grenade lands — hold G to cook one so it airbursts on arrival, and watch the fuse bar, because holding it too long detonates it in your hand. Grenades arc, bounce off walls and wrecks, and roll to a stop; damage falls off with distance and is cut sharply for anything hiding behind cover.

The melee bash interrupts whatever you are doing — including a reload — and knocks a target back. That is the point: it is the answer to something already inside your guard.

Hostiles

Type	Behaviour
Scavenger	Fast melee rusher, closes to contact
Raider	Rifleman, holds ~13 m and fires in bursts
Breaker	Shotgunner, pushes to close range (wave 3+)
Marksman	Takes high ground and hits for 26 (wave 4+)
Juggernaut	Heavy, 420 HP, suppressing fire (wave 5+)
Warlord	Elite juggernaut that closes out every fifth wave

About one building in three has a ground floor you can walk into — the ones with a concrete ground storey and a shopfront of piers, rust shutters and windows over a sill. Inside is a dim shop under the floors above: columns, aisles of shelving, a counter, tables, crates. It is cover from a marksman on a roof, whose sight line the floors cut, and a fight at close range through doorways and windows; a jump indoors stops at the ceiling, and so does a grenade. Hostiles follow you in, a warlord stooping under the ceiling to do it. The shelving still holds what nobody took, the counter still has its panel and its kick, and dead strip lights hang from the ceiling, a few by one end. The floors are what a looted shop leaves: paper drifted along the walls and blown in at the doors, plaster down from the ceiling, and glass under every window.

Most of the lower ones go further: a stairwell in a back corner of the shop, switchback flights of concrete steps climbing lap over lap to a bulkhead on the roof, and the roof itself somewhere to stand. A waist-high parapet runs round it on the street sides — cover from the street, and a shot down into it — and a party wall too tall to jump stands where the building next door is a metre away. A couple of plant boxes give cover from the other roofs. Hostiles follow you up: while you are on a roof or in its stairwell, the route field is built from the stair's door, every hostile that can fit under the flights walks there and climbs after you, and they come back down the same way when you leave. A ranged hostile with a clear shot at the roof from the street takes it instead, and one on the roof with a shot down holds it. A juggernaut comes up stooped under the flights; a warlord is too big for the stairs and waits below.

Those buildings are floors all the way up, too: every lap of the stair lands at one, through a door in the stairwell's wall. They are gutted frames — concrete floors with brick, render or stone between them, in the building's own style, so you can tell them from the street — with real windows all round: you see out of them and shoot out of them, and whoever is in the street does the same back. A floor has a crate or a table to take cover behind, glass under its windows, and the hostiles follow you onto it, round the stairwell, and back down after you when you go.

They use the buildings against you, too. Go into a shop and up to two of the riflemen take posts outside, each with a sight line into a doorway, and hold them while the rest come in after you — so the door you leave by is covered. Go up onto the roof and two of them wait in the shop below instead, covering the stair door you will come back down through. A hostile that has lost sight of you, or knows you are inside, throws a frag: from the second wave on, a raider, a breaker or a juggernaut carries one, and it only lets go of a throw it has flown first through the same bounce the grenade will take, so what you hear land is in the room with you. One frag in the air at a time, a call when it is thrown and a GRENADE warning when it lands near you — move. And your reload is their window, the way theirs is yours: change magazines or weapons with hostiles within 25 m and they stop holding, give up their posts and come for you, faster, until a second after you are ready again. The first one shouts.

Hostiles route around buildings rather than walking into them: a coarse walkable grid over the city carries a cost field rebuilt from wherever you are standing, so one that loses sight of you takes the way round the block, or in through the doorway of a shop you are hiding in, instead of sliding along the wall between you. With a clear view it comes straight at you, as it always did.

A marksman claims a rooftop, a terrace or a window on a floor of a building — the one in each building with the longest view of the street — and stays there while it can see you. Before each shot it paints you with an aiming laser for about a second — that red line is your warning to break line of sight. Warlords are outsized, carry roughly 1100 HP, wear a gold band, and get their own health bar at the top of the screen.

They hunt by sight, by proximity and by the sound of your gunfire, steer around buildings and wrecks, strafe while holding their preferred range, and hold fire for a beat after spotting you. Health scales ~9% per wave.

Each archetype wears its own kit — plate and pauldrons, a carrier and pouches, scrap strapped on one side, a hood and a long coat — so you can tell what is walking toward you before the marker band is legible.

Waves grow each round, hostiles trickle in rather than appearing all at once, and clearing a wave awards a score bonus plus an ammo resupply. Kills sometimes drop an olive ammunition can with its lot stencilled on the side, a moulded medical case with the first-aid sign on it, or a frag, each over a soft halo in its own colour — amber, green, red — so you can find one across a street at dusk. Health regenerates five seconds after you stop taking fire. Your best wave and score are kept between sessions.

The buildings are worth going into. Some shops and some of the floors over them hold a cache, stashed at the back of the room against a wall or a fitting: an ammunition can, a medical case, or an armour plate under a blue halo, which nothing else gives you. A plate puts 50 on the blue bar over your health, and while it lasts it takes 60% of every hit out of itself. Caches are put back at the start of each run and lie where they are until taken.

The armoury

When a wave is cleared, B opens the armoury for the intermission, which waits while you shop. It sells:

Item	Tiers	What it does
Plate carrier	3	15%, 28%, 40% off every hit you take
Extended magazines	2	A quarter more in every magazine, then half as much again
Optics	2	Tighter aimed fire and a closer sight picture
Match ammunition	2	12%, then 25% more damage from every weapon
Frag pouch	2	One more grenade carried each, and the pouch filled
Resupply	—	Every weapon to full ammunition, and two frags
Field dressing	—	Back to full health

It is paid for in scrip, which every point you score earns and which shows under your score. Spending it costs no score, so buying armour is never a choice between surviving and your best score. What you fit lasts the run.

The operation

Eleven weeks ago the Halloran refinery burned for nine days and buried the city of Carrow in ash. The city was evacuated, and not everyone got out. The Cinder stayed: looters at first, now a militia of a few hundred under warlords, holding the city street by street and anyone left in it. That is who is coming at you, and why. They hold Sector 7 and you are in it.

You are WREN, a recovery contractor. HALCYON is your handler, and the only voice on your radio. The job: bring the district's dead relays back so the survivors still holding out in there can be found, get them out, and hold the depot when the convoy comes for the last of them.

DEPLOY opens the briefing; REDEPLOY after a death goes straight back in. A run is three acts over twelve waves, each wave bringing the objective the operation's plan gives it, and HALCYON calls each act, each wave and each objective over the radio in the bottom left:

Act	Waves	What it is about
I · Dead Air	1–4	The first relay, a stockpile, a fuel dump
II · Holdouts	5–8	A warlord, the first survivors, a lieutenant with the routes
III · The Convoy	9–12	More survivors, another dump, then the depot

Wave 12 brings the convoy: hold the depot while it loads, and the operation is complete. If it cannot hold, it comes again the next wave until it is out. After that the city does not stop, and the objectives keep coming in turn. When you go down, the debrief says how far the operation got and what you did for it.

Objectives

Wave survival on its own rewards standing still in the best cover you can find, and the other 270 m of city may as well not exist. So most waves put something worth having at the far end of it and start a clock.

Objective	Where	What it asks	What it pays
Supply cache	40–80 m out	Stand on it for 4 s	Ammo, frags, 300 × wave
Beacon	40–75 m out	Hold a 6.5 m circle for 18 s	Ammo, 35 health, 500 × wave
Relay mast	On a roof, 25–120 m out	Find the stairwell, hold the mast for 20 s	Ammo, 25 health, 600 × wave
Fuel dump	A burning drum, 30–90 m out	Plant a charge (3.5 s), keep them off it for 18 s	Ammo, a frag, 600 × wave
Lieutenant	Crossing the sector	Kill him before he reaches the far edge	Ammo, two frags, 700 × wave
Holdout	In a shop, 30–95 m out	Cut them loose (2.5 s), walk them to a pickup	Ammo, 50 health, 800 × wave
Depot	45–95 m out, wave 12	Hold a 7 m circle for 40 s	Full heal, full rearm, 1,500 × wave
Evac point	55–105 m out	Reach it before the window shuts	Full heal, full rearm, 750 × wave

One runs at a time. Wave 1 is left clean so the first contact is about learning to shoot; an evac window opens instead when a warlord goes down. The newer four each ask something different of you:

• A relay is up a stairwell on a roof, and only counts from the roof. Where no stairwell is in reach, HALCYON sends you to a beacon instead and says so. Holding it brings the sector up the stairs after you.
• A charge, once planted, draws every hostile that cannot see you to the drum. One that reaches it while you are more than 6 m off pulls it. When it blows it is your blast, so stand off and let it take whoever is near.
• A lieutenant walks his own route to the edge of the sector with three escorts beside him, and shoots at you on the way without stopping. Get there first.
• A holdout follows you once cut loose, by the same routes the hostiles use. They are not a target and your rounds pass them, but anything near wears them down, and a blast hurts them like anyone else. Every other one has gone to ground up a building: find the stairwell, cut them loose on their floor, and they come down the stair behind you.

Progress bleeds back if you are driven off rather than resetting, so being pushed out costs ground without wiping the job, and a beacon transmits — working one pulls hostiles in from 55 m while you stand there.

Finding the site is most of the problem, because one ruined block looks much like the next. A light column marks it, occluded by whatever is in front of it so it reads as a bearing over the rooftops rather than a decal; a waypoint tracks it on screen and pins to the edge when it is behind you; the radar holds it at the rim when it is past the sweep.

The payouts sit above a wave-clear bonus on purpose. Crossing the sector under fire should beat holding the plaza — otherwise there is no reason to leave, which was the problem to begin with.

Looks

Dusk, and the light is doing the work. A single warm key sits low in the west with a cool sky fill opposite it, so a wall tells you which way it faces before you read anything else on it. The sun is a sprite placed at the light's own direction rather than painted into the sky, so it can never drift away from the shadows it casts. Fog is tinted to the sky's horizon, which drains colour out of distance.

Every texture declares how many metres of world one copy of it covers, and the geometry is unwrapped to match, so nothing in the city is stretched or crammed. A facade tile is 10 m: four window bays and three floors, which puts a window at about a metre and a half and a floor at three and a third. Wall UVs are snapped to those, so a window is never cut in half at a corner and the floor lines meet the ground and the roof square.

One thing refuses to live in a texture at all, and that is the paint on the road. A tile repeats, and a centre line painted into the asphalt comes out as a grid of stripes over the whole sector — across the sidewalks, across the lots, everywhere except down a street — because the one thing a marking needs is the one thing a tiled image cannot have, which is a position. So the shape of every marking is geometry, laid off the same grid the lots are: a centre line down each street, dashed or solid, edge lines inside both kerbs, zebra crossings on the junction approaches with a stop bar behind each one and an arrow in the lane that gives way. The texture underneath carries only how worn the paint is — chalked edges, tyre scuffs, stretches rubbed back to the aggregate — and roughly one marking in six is missing outright, which is what a decade without maintenance looks like. Some kerbs carry parking bays or double yellow lines instead of an edge line, and a few junctions are yellow boxes, hatched corner to corner. Set into the road are cast-iron manhole covers and gully grates in the gutter. At each end of every zebra the kerb is dropped to a lip over the road, the pavement ramping down to it with flared sides, and the ramp is laid with buff blister paving; where both streets at a corner are crossed, the two ramps meet in a dish and the paving turns the corner. Every piece of ironwork asks the ground under each of its corners and is only laid where they agree, so nothing hangs off a kerb. It costs the layout nothing: like the rest of the decorative pass it draws from its own generator, so a seed lays out exactly the city it did before.

The sector is not the edge of the world. Past its wall the city carries on along the same street grid: blocks of every facade, some gutted to a shell, some with their tops broken off, thinning out over waste ground that rolls away to a line of hills, with rubble heaped against the outside of the wall. Its streets carry on too, paved between the lots, and every block throws its long evening shadow across them. From any roof you look out over a city the haze takes away, rather than over a strip of asphalt and then sky. None of it can be reached or shot, so none of it is anything but a picture.

A window is a hole in the wall, not a picture of one. The facade's own shader knows where every opening is — the same four-by-three grid the walls are snapped to — and traces each one: a reveal a quarter of a metre deep that catches the sun on one side and shades the glass on the other, intact glass set back in it mirroring the sky, boards nailed across the back of the opening, and behind a blown-out pane a room — floor, ceiling, walls — dim and darker the further in, with a low sun laying a patch of light across the floor. It is all parallax in the material, so it moves the way a recess moves as you walk past, and none of it is geometry: it costs no draw calls, no triangles and nothing on the seeded stream, and a bullet still stops at the wall face.

Surfaces carry a normal map derived from their own texture — the painted mortar lines and pitted concrete become relief that catches the key light instead of reading as a decal. They carry a roughness map from the same luminance, so soot and grime answer the light flatly while glass and bare metal stay sharp enough to reflect. Facades are built with broken, boarded and intact windows, sills and lintels, grime bleeding from every sill, scorch licking up from the blown ones, bullet pocks and the odd shell crater with reinforcing bar still standing in it. Each of the five wall materials — precast panel, brick, curtain wall, render and stone — is painted in several variants, scrap steel comes in four paints failing to the same oxide, and every building is given a colour drift and a tile offset of its own, so two neighbours never read as the same prefab. Tall blocks step back near the top, which is most of what gives a skyline its shape.

Weathering is fractal rather than drawn. Every stain, wash and bloom of rust is a warped noise field thresholded to a ragged edge, uneven inside and present at every size at once, because the soft round blotches it replaced read as polka dots on every surface they covered. It wraps at the tile edge like everything else, so the eye has no seam to find.

Where surfaces meet, the light does not reach, and a shadow map will not tell you that. Every solid in the city deposits into a coarse occlusion grid, and the ground reads it back as vertex colour when the city is merged — so the gutter beside a wall, the inside of a corner and the strip under a wreck all darken, and walls fade toward their own footing. It is baked once, costs nothing per frame, and is most of what stops a city of right angles looking like a city of boxes.

The sky, the sun and the air between them are one model, so they agree about what time it is. The sun stands 24 degrees up at the long end of the afternoon; the sky is computed rather than painted — blue overhead, a warm horizon on the sun's side and a cool one opposite, a bright haze around the sun from forward scattering, and a small, very bright disc whose glare is the bloom's doing. The same function is rendered into an environment map that lights every surface, so a wall turned to the sun is warm and a wall turned away is lit by blue sky. And the air is not one flat colour: dust hangs thicker at street level than at roof height, and it takes the colour of the horizon in whichever direction you look — warm toward the sun, grey away from it — so a building far down a street fades into exactly the sky behind it.

Where things meet, they darken. A screen-space ambient occlusion pass works out, for every pixel, how much of the sky above it is blocked by something within a metre: the foot of a barrier, the gap under a car, an inside corner, a hostile's boots. Contact shading is the first thing the eye uses to decide whether an object is standing on the ground or pasted over it.

The sun casts two shadow maps, not one. A wide map covers the sector, and a tight one — about a centimetre a texel — covers the street in front of you, where you are actually looking, blended into the wide one at its edge. Both are snapped to whole texels, so shadow edges hold still while you walk instead of crawling along the walls.

The frame is then finished rather than shown raw. It is drawn into a floating point buffer, everything brighter than white is blurred into a bloom (the sun, the barrel fires, a muzzle flash), and one final pass tone-maps, grades the image a little less saturated than life — dust takes colour out of everything — vignettes, and lays a fine grain over the top.

Nothing in the sector is a plain box any more, and that is mostly about shape rather than pixels. A wrecked car is drawn the way a car designer draws one, by its side view: one outline with the wheel arches bitten out of it, a nose that drops to the bumper and a boot that falls away, extruded across the car with its shoulders rolled over and then pinched in toward both ends and tucked in at the sills. The greenhouse is glass leaning in as it rises, with painted pillars and a roof laid over it, so the windows sit in frames; the wheels are turned on a lathe, a tyre with a sidewall and a tread round a dished rim, under a dark wheel well. The rusted ones wear their own paint gone to primer and oxide rather than a container's corrugated sheet, and the whole car fits the box you climb onto — its roof is the deck you stand on. Half of them are pickups with an open bed, and the burnt-out ones are the same panels in charred steel with no glass left. A jersey barrier has the splayed foot and the kink at knee height that make it a jersey barrier; a shipping container has corner castings, sill and roof rails and doors with locking bars; a burning drum has its rolling hoops.

Hostiles are bodies, not stacks of boxes: a chest broader than the waist, a thigh tapering to the knee, a calf, a gloved fist, a boot on a sole, a head in a gas mask whose goggles glow — each piece swept along its own line or turned on a lathe. And they are wearing something, cut from the body's own shape so a plate lies on the chest it is strapped to. A raider has front and back plates on a cummerbund, shoulder straps, magazine pouches and a radio, under a helmet with ear defenders; a breaker a vest all round with a trauma plate, tassets, a neck guard, pauldrons and a guard over its jaw; a juggernaut all of that heavier, with two-layer pauldrons, a gorget and a pack of two tanks whose hoses run over its shoulders; a scavenger a hood, a sheet of tin over one side of its chest, a bandolier and one pauldron; a marksman a hood, a chest rig and a coat. A coat hangs from the hips rather than the waist, so the shoulders can turn into a stance without swinging it through a leg. That is not decoration: a wave is read at forty metres against a dusk skyline where the archetype's colour is barely a colour, and the outline is what tells you what is coming. So are their weapons, drawn by their side view like yours: a rifle with its magazine curving forward and a stock, a breaker's shotgun over its magazine tube, a marksman's scoped rifle, a juggernaut's drum-fed gun with its bipod folded, a scavenger's hook. The kit is merged into the parts that already take hits, so what you can see is what you can shoot. The cloth and the webbing are painted pale on purpose, because a texture multiplies the colour on the material — put a mid-grey weave under an olive drab coat and every hostile is a silhouette.

What they drop is drawn the same way as their guns, by the side view and the lathe: a pressed-steel ammunition can with its lid, hinge, cam latch and folded bail handle; a medical case in two moulded halves with ribs, a handle and draw latches; a grenade turned round its yellow band, under a fuze with its spoon and pin.

They move like people carrying weapons. Knees and elbows bend; the stride is paced to the ground covered, so a planted boot does not skate. On patrol a rifle is carried low across the body; once a hostile has seen you it squares up, blades its shoulders into a stance with its head on you, shoulders the weapon and follows your height with it. Both hands stay on the gun through all of it, because the arms are solved to reach the gun rather than animated beside it. A hit shoves the upper body the way the round was travelling and it comes back on a spring; a kill buckles the knees before the body follows the shot down.

Hostiles carry a contact shadow under them, because the sun's shadow map only covers the ground near the player and anything beyond it would otherwise float.

Graphics settings

Shadow mapping costs more than everything else in the scene put together, so it is the first thing the quality tiers drop:

Tier	Shadows	Lighting	Fire lights	Post	Pixel ratio	Dust	Weeds
High	2048 wide + 2048 near, soft	PBR + sky, normal maps	nearest 3	occlusion, bloom + grade, 4x MSAA	up to 1.25	yes	yes
Medium	1024 wide + 1024 near, hard	PBR + sky, normal maps	nearest 2	occlusion, bloom + grade, 2x MSAA	up to 1.0	yes	yes
Low	off	Lambert	none	off, straight to the canvas	1.0	no	no

A machine that cannot afford shadows cannot afford a bloom either, so Low drops the whole post chain and hands tone mapping back to the renderer. It is meant for the integrated graphics in an older laptop, and it draws the city with plain Lambert lighting under a brighter sky light instead of the physically based model, with no point lights at all; the gun in your hands keeps its full materials. Under software rendering that is 176 ms a frame against 986 for what Low used to be. On every tier only the nearest few fire barrels cast real light — a fire's light reaches 14 m, and every barrel in the sector used to be paid for on every pixel.

The sky carries weather: a layer of broken cloud lit gold on the sun's side and slate underneath, which the city's reflected light picks up too. And the city is overgrown — weeds along both sides of every kerb, against the foot of every building and through the cracks of the pavement — which is the strongest single thing that says nobody has swept here in years. Weeds are walked and shot through, as grass is. Low keeps the cloud, at fewer octaves, and drops the weeds.

Rain has been and gone: puddles lie in the gutters and the dips of the road, dark and mirror-smooth, showing the sky above them with the sun as a small glint, each inside a ring of damp asphalt. Paper, card and plastic have drifted against the kerbs, and chips of brick and concrete lie along the foot of every wall. The weeds move in a breeze that runs down the street rather than through every tuft at once.

The pixel ratio is the column that matters most. Every pass the post chain adds is paid per pixel, and on a 2x screen High used to draw 3.06 times the pixels of a 1x one — measured in software at that ratio, a frame cost 5,968 ms at High's old cap and 3,287 at 1.25. Above 1.25 the picture is sharper by an amount nobody notices while a hostile is shooting at them.

The default is Auto. It starts by timing a few frames of the city at each tier behind the loading screen and picks the best one that draws an empty street in 12.5 ms — 60 frames a second with a third to spare, because a fight costs about that much more — so a laptop that cannot afford High starts below it rather than earning its way down in the first fight. Then it keeps watching for as long as you play. Over any three seconds under 55 frames a second it gives something back and tells you what: in a fight, resolution, 15% at a time down to 70% of the tier's, because that costs no stall; between waves, a whole tier, because changing tier rebuilds the shaders and that hitches. If a fight is still short once the resolution is spent, it takes the hitch and drops the tier anyway. It never steps back up. Picking a tier yourself in the pause menu turns all of it off — an explicit choice is never overridden.

Press ` (the key left of 1), or tick Show frame rate in the pause menu, to see what your machine is doing: frames a second, the frame time and the worst one, how much of it the CPU took, the tier and resolution in use, draw calls, whether the mouse is captured, and the name of the GPU the browser is drawing with. If that last line says SwiftShader, llvmpipe or Basic Render, the browser is not using your graphics card at all — turn on hardware acceleration in its settings. The menu says so too. Until you do, auto starts such a browser on low at 70% of its resolution and goes down to 40% if it has to, which is what keeps it playable with every pixel drawn by the CPU.

A slow frame no longer slows the game down. Below 20 frames a second the simulation used to take one 50 ms step per frame whatever the frame took, so walking, falling and every hostile ran in slow motion; a long frame is now split into steps, up to a fifth of a second.

Every shader a run needs is built, and every texture uploaded, behind the loading screen, so the first hostile you see and the first shot you fire do not stall the frame they happen in.

Vertical ground

The city is not flat. Raised terraces of collapsed floor and stacked shipping containers are scattered through the blocks, each reachable by a stair run of half-metre steps — low enough that you simply walk up them, no jumping. Take the high ground and the ground-level hostiles lose their shot at you; step to the edge and you get yours.

Anything between a step and chest height is climbed rather than walked around: hold Space facing a car roof, a planter or a low wall and you haul yourself up over about half a second, ducked and unable to shoot until you top out. Hold it through a jump and the reach extends to roughly two and a half metres. Hostiles climb after you. Stand on a car roof, a crate or a low wall and a hostile coming for you — a scavenger, or anything that has lost sight of you — walks to the face and hauls itself up the same way you did, only slower, and with its weapon off you until it tops out: a car roof buys you that second and a half, not the fight. Once up there with you it holds the deck rather than strafing off the edge. Marksmen never climb; they hold their roofs.

Hostiles run dry. A rifle's magazine, a breaker's six shells, a marksman's five rounds and a juggernaut's drum each end in a reload — two to three seconds with no fire coming from it, and the magazine out, the fresh one in and the bolt are heard from where it stands. Watch for the gun dipping and the hand going to the magazine: that is your moment. If it has cover beside it that would hide it crouched and not standing, it kneels behind it to reload and stays there. And gunfire too far off to bring a hostile running still carries: an unalerted one in the ring beyond turns its head toward the shot.

The same rules apply to everyone: hostiles climb, stand on, and fall off the same surfaces, and a melee rusher cannot reach you across a height gap too tall to climb. Drops of more than about four metres hurt, and a long enough fall will kill you.

The ground you see is the ground you stand on. The pavement round every block is a 28 cm kerb above the road, and the plaza, the rubble lots and the ruins' courtyards are slabs of their own; you step up onto them, hostiles stand on them rather than in them, and a shot at the pavement stops at the pavement. Stepping up a kerb or a stair moves your feet at once and eases the view up after them, so a street crossing is not a jolt — and at a zebra there is no step at all, because the kerb is dropped and you walk up the ramp you see.

Some shop doorways — about one in six, wherever there is room for them to swing — hang a pair of painted steel doors that open into the room, each leaf with a wired-glass vision panel and a push bar. Shut, a door is a wall: it stops you, a sight line, a round and a grenade. E opens or closes the one in front of you, and it will not shut on anyone standing in it. A door hides you; it does not hold anything out. A hostile that walks up to a shut door opens it and comes through, so shutting yourself in buys you a moment of not being seen and the sound of it opening.

The fire barrels burning in the streets go up. Two pistol rounds or one from the shotgun hole a drum, it roars for half a second, and then it blows with a frag's force and a quarter more reach: whatever is standing by it, hostile or you, takes the blast, and a kill is yours if you set it off. A frag or another drum's blast that can see a lit drum sets it off a beat later. What is left is a crushed, burnt stump you step over, smoking for half a minute.

About half the windows still have glass in them — in the shops and up the floors. A pane is no cover and stops nothing: a round, a sight line and a grenade go through a window exactly as through an empty one. It only breaks: under a round passing through it, a blast that reaches it, a body climbing through it, or a hostile's first shot from behind it, so a marksman at a window gives itself away with the sound of glass going. The shards fall to the floor under them and lie there a while.

Crouch out of a sprint and you slide: down to knee height, faster than the sprint for a moment and bleeding off over most of a second, and a jump out of it keeps the speed. A slide into a wall stops at the wall. Hold Q or E to lean: the head goes out about half a metre past a corner while the body stays behind it, and never into a wall. A tap of either still does what it did — cycle the weapon, work a door. Leaning works both ways: a hostile looks for your head, so a head out past a corner is a head it can see and shoot.

How it is put together

index.html          page shell, HUD markup, import map
src/main.js         game loop, scene/lighting setup, waves, hit resolution
src/city.js         procedural city generation
src/world.js        box collision (square or turned), ground height, line-of-sight
src/nav.js          walkable grid over the city, and a route field to the player
src/player.js       input, movement, camera, health
src/weapons.js      weapon definitions, view models, firing and recoil
src/enemies.js      hostile archetypes, AI, procedural bodies
src/objectives.js   objective sites, channels, stages, the cast they put on the map
src/story.js        Operation ASHFALL: the briefing, the acts, the plan, the radio
src/grenades.js     thrown frags: fuse, bounce physics, detonation
src/barrels.js      fire barrels: shot, fused, blown, chained, left a stump
src/glass.js        the panes still in the windows, and their shards
src/effects.js      pooled tracers, impacts, blood, casings, explosions
src/textures.js     canvas-painted textures (asphalt, facades, rust, cloth, sky)
src/shapes.js       chamfers, lofts, side profiles, lathes, creased normals, merging
src/post.js         ambient occlusion, bloom, tone mapping, grade, vignette, grain
src/atmosphere.js   the sky, the sun and the fog, as one model
src/shadows.js      the sun's two shadow cascades
src/windows.js      window openings traced in the facade shader: reveals, glass, rooms
src/audio.js        synthesised gunfire and feedback via Web Audio
src/hud.js          HUD readouts, killfeed, radar, damage indicators
vendor/             Three.js r169 build

A few notes on the implementation:

• Nothing is loaded from disk or network. Every texture is painted into a canvas at boot, every sound is synthesised from noise bursts and oscillator envelopes, and every model is assembled out of chamfered boxes, side profiles, lathes, and sections swept along a line.
• What you can see, you can bump into. Every heap of rubble carries colliders cut to its own shape — a stack of tiers shallower than a step, each fitted to the heap's cross-section at that height — so a mound stops you at its foot and you can scramble up it with any part of you on it, and it stops a bullet. A fallen slab of floor lies with one edge on the lot and leans up from it, and its own plane is what you walk up, stand on, see over and shoot. A gutted ruin's windows are real holes in its walls: you see through them into the courtyard and shoot through them, and so does whoever is in there, and its walls come down at the top in broken steps where the floors tore away. A heap is a slumped mound of broken concrete and brick, not a boulder. A container's steel is folded and a shop's shutter is slatted, in the shape rather than painted on, so a low sun lights one side of every rib. A closed block's ground floor is a row of shopfronts onto its street — piers, a fascia, and in each bay a window, a door, a shutter or the opening blocked up. A crate is boards nailed into a frame, bare pine, silvered, stained or painted olive with its lot stencilled on, not a little container. Containers, wrecks, barriers, drums and lamps stand clear of one another, inside the sector, and on the floor under them — a barrier on the pavement stands on the pavement — and the plaza's dry fountain is a basin you can climb into, round a plinth that stops you.
• You hear where things are. A hostile's shot, a round striking a wall, a hit, a blast, a grenade skittering and a hostile's shout are each placed where they happened, through an HRTF panner, with the listener riding the camera — so fire from behind you sounds like it, best on headphones. So are their footsteps, twice a stride off the same phase their legs are drawn from, heavier for the armoured ones and hollow on a car roof: a flanker is heard working round behind you before it shoots. Your own gun and footsteps stay centred, and the echo off the buildings comes from everywhere.
• Normal maps are generated, not authored. A Sobel pass over each texture's own luminance becomes its normal map, so painted detail lights like geometry without shipping a second set of images.
• Big soft shapes are painted small and scaled up. A canvas filter blur costs a full-canvas convolution per draw call, which made stains and rust blooms the most expensive thing at boot. Low-frequency detail is painted into a 96px layer instead and the upscale does the smoothing — the same picture, and boot got faster rather than slower as textures got richer.
• Changing how it looks cannot change what gets built. Three draws four random numbers per material, texture and geometry to build a UUID, off the same seeded stream the city is laid out from, so adding a texture used to hand every seed a different city. Boot-time graphics now run inside a call that rewinds the stream afterwards, and the decorative pass over the city draws from a generator of its own — so a seed lays out the same streets whether or not the buildings are wearing any of their detail. A prop is the harder case, because its collider the city: a wreck builds its shape inside the same rewind and then pays a fixed number of draws for what it used to cost, so it can be rebuilt out of fourteen shapes instead of seven boxes and stay parked in the same street. A check pins three seeds to a fingerprint of every collider's position and turn.