How the city grows
Nothing in this city was modelled or painted. There are no files behind it: one number, the seed, goes through a chain of rules, and every rule asks a hash of the seed for its choices. The same seed always gives the same city, down to which rooms have their lights on.
Streets and lots
The ground is cut by a grid of streets every 170 m. Each line of the grid draws its own width, so some streets are narrow slots and every fourth is a broad avenue. Each block between them is split into lots, and a few lots are merged for the biggest towers.
Towers
A tower is a stack of segments. Each segment steps back or juts out a little on every side, the top third narrows into a crown, and boxes of extra rooms hang off the street faces. The height comes from a smooth field over the whole map, so tall districts rise and fall, with a few spires far above the rest.
Rooms behind glass
The facades are flat boxes. Windows, recesses and the rooms behind them are drawn per pixel: the shader follows your line of sight through the glass into a room with a floor, a ceiling, walls, blinds and furniture, so each room shifts in parallax as you fly past. Whether a room is lit, and in what colour, is a hash of the tower and the window.
Traffic
Every street carries sky lanes at fixed heights, in both directions, with streets crossing at different heights so lanes never meet. Cars come in platoons that surge and drop back together, each with its own line, height, size and paint. A car's place on its lane depends only on the time, so thousands of them cost almost nothing, and the one you follow is the same arithmetic.
Your car
A wedge of brushed steel folded from flat panels, with hover discs where the wheels would be. It flies a guided route down the street centres and turns at the wide crossings. You help it along: lean it across the street, climb or dive to another level of traffic, open it up, or hold a side before a crossing to turn there. Let go and it finds the middle of the street and the nearest level again. The traffic makes room as you pass through its lanes.
From the driver's seat you ride inside it: the screen across the dashboard shows the autopilot's state, your speed and height, the route ahead from above and the next turn, and the path it plans is drawn in the air in front of you. Turbo opens the electric drive right up, to 540 km/h on a straight: the hover pods burn white, arcs crawl over the hull, plasma streams from the vents and the tail lights draw red trails that hang in the air. It still brakes for every turn.
Hover brings it to a stop wherever it is and holds it there, rocking a little on its pods. Once it is still the doors rise: gull wings, each hinged along the roof's edge, the leather lining and its line of light rising with them. Take the seat and the street is open beside you. Ask again and the doors come down before it flies on. The camera in its tail shows on a slim screen standing on the dash, so nothing hangs in the windscreen.
In the sky
Far above the city a station turns: a habitat ring 1.5 km across round a hub, a spine with solar wings, radiators and a drive, shuttles coming and going, and a tether falling from it to the horizon with climbers riding up and down. It is far enough away that it stays where it is as you fly, and the frame draws it as part of the sky, through the whole depth of the air and behind the clouds.
Parametric towers
In the tallest districts a few lots grow something else: one section, a superellipse, lofted 450 to 700 m up, swelling a little low down, tapering toward the top and turned through as much as 90° on the way. White fins follow the turn and run on past the roof into a crown. Three quarters of the way up is a sky lounge, three floors of glass cantilevered out over the street with a pool on its roof.
Megastructures
Every few square kilometres a block grows something no developer would. The Spire is a glass needle 1.4 km tall inside a cage of light: 24 straight struts leaning both ways make a hyperboloid, pinched at 340 m and flaring into a crown 300 m across at 1 km, bound by rings of light round a glass eye. The Gate is a catenary 780 m high standing in two plazas and vaulting the block between them and two streets. The Skyport floats 450 m over a low district on rings of light: a saucer 224 m across with a glass dome and three towers on its deck. The towers round them are kept below them. Click one to read it.
Air and light
The sky is worked out from sunlight scattered by air, haze and ozone, marched through the atmosphere for every direction whenever the sun moves; the haze takes its colour, and a deck of cumulus drifts over the city and drops its shadows on it. The fog is thick at the bottom of the canyons and thins with height. A height map of every tower tells each wall how much sky it sees and which wall stands across the street, so a wall in shade takes warm light from the sunlit one opposite, and windows and paint reflect the towers they face. Close to you, balconies, AC units and cars cast their own shadows.
Anime
The same city can be drawn as cel animation, in two eras. 90s is a cel shot on film: dark ink wherever the depth jumps or a surface turns, the sunlight painted in three flat tones so a shadow falls as one hard shape, every window a flat cell of colour, the grime painted out, clouds with drawn edges lit in two tones, the shade mixed toward indigo, a warm glow round each light as if shone through the cel, and grain. Modern is a polished feature: finer lines in a darker shade of the colour under them, softer steps of light, a more vivid sky and haze (rose and violet at twilight), clouds lined with sunlight, a wide flare, the sun's light leaking in from its side of the frame and a sparkle on the brightest lights. The lines are found in the depth and the angle of every surface, not in the picture, and the steps of light come from the sun's angle and the shadow, so everything moves and lights as it did.
Keys
A D or ← → lean and slide across the street; hold one before a crossing to turn there · W S or ↑ ↓ climb and dive · hold ⇧ for speed · ⇧T turbo · ⇧H hover and open the doors · ⇧V the driver's seat (drag, or Q E, to look around) · Q E turn the camera round the car · C director · R back to your car · ⇧F drone (then WASD fly it) · + − zoom · drag to look around · click a car to follow it, a tower to read it · 1 2 3 sky · [ ] traffic · ⇧G new city · ⇧B blueprint · ⇧L sky lanes · ⇧N labels · ⇧P graphics preset · ⇧I anime: off, the 90s or modern · M sound · Space pause · ⇧O the radio · ⇧Y its video on the hologram or down on its card · ⇧U let the panel fold away when idle, or keep it open · / hide the interface · ⌘' render tuning. On a touch screen, drag to steer.