Build a single-file HTML landing page for "Solstice", a fictional compact-fusion company, where the first 6000px of scroll is a story: the sun sets over a layered landscape, night falls, stars come out, and only then does the page arrive. Space Grotesk, Inter and JetBrains Mono from Google Fonts; GSAP 3.12.5 and ScrollTrigger from cdnjs; everything else inline. No images - the landscape is one inline SVG, the reactor is canvas, the icons are inline SVG. Say in the footer that the company is fictional, and credit the parallax landscape to its original artist if you build on one.

THE STAGE
One SVG fixed to the viewport, viewBox 750 by 500 with preserveAspectRatio "xMidYMax slice", so the hills always meet the bottom edge and the sky crops at the top on wide screens. Give it a white background: the sky rect is a radial gradient at 80 percent opacity and the colours were chosen over white, so it goes muddy over anything darker.
Three scenes stacked in that one SVG: scene 1 is dusk hills, trees and two banks of cloud; scene 2 is a second, darker range that rises from below; scene 3 is the night sky with its own radial gradient, a star field and a final range of hills. Paint every layer with linear gradients from peach through rose to plum and navy, darker the nearer it is.
The scroll distance is a 6000px empty element behind the SVG, and a 6000px spacer in the flow so the real content starts after it. Every trigger is keyed to that element - a percentage of it or a pixel offset into it - so its height and the trigger timings change together or the scenes overlap.

THE SUNSET
All scrubbed, never timed. Over the first 45 percent the near hills drop and drift sideways at different rates and the cloud banks part to the edges. The sun is the centre of the sky's radial gradient: animate its cy from above the frame to below the horizon and widen its colour stops as it goes, so the glow spreads as it sinks. Then the second range rises in staggered layers, the sky's outer stop darkens to plum, and from 60 percent the night scene slides up from below with the stars fading in and a few of them twinkling on their own loops. A single falling star crosses late: draw it as a short SVG line with a white-to-transparent gradient plus a soft radial glow at the head, never a hotlinked image.

THE HERO AND THE STORY
The hero sits over the bright sky in deep plum ink, centred: a mono eyebrow pill with a pulsing dot, a two-line display headline ("A sun that never sets."), a lede and two pill buttons. It fades and lifts away over the first 9 percent of the scroll.
On wide screens the slice-scaled hills climb behind the lede and the secondary button, and dark plum text over dark purple hills disappears. Put a soft peach radial haze behind the hero copy, ending just under the buttons, and give the ghost button a pale translucent fill with a backdrop blur. Hide any scroll-down arrow that ships with the landscape - it lands on the buttons.
Two captions tell the story mid-scroll, each fading in, holding and fading out inside its own scroll window: "The sun sets. Demand doesn't." at the peak, "Firm power, all night long." once it is night. Put them in a glass pill with a mono timestamp above, so they read over both the yellow sun and the night sky.

THE NAV
Fixed, transparent and plum over the sunset; after 140px it turns to dark glass with light text. Under 760px it collapses to a three-line burger that opens a full-screen menu: big numbered links that stagger in, a full-width call to action and a live status line. Lock the page scroll while it is open, close it on Escape and on any link, and close it if the window widens past the breakpoint.

THE PAGE AFTER DARK
The content sits on near-black ink, z-index above the fixed SVG, with a gradient fade on its top edge so it rises out of the night rather than cutting across it. In order: a four-up stats band with sun-to-pink gradient numbers; four technology cards (magnets, plasma control, breeding blanket, power cycle), each with a mono index, an icon tile, a paragraph and a dashed-rule spec line; the reactor; a manufacturing split with numbered steps; a vertical, scroll-driven milestone timeline (a sticky left column with the heading and a giant sun-to-violet gradient year that rolls to the milestone being read, a status line and a 2023-2032 meter; on the right a rail that fills to a reading line 55% down the viewport with a glowing comet at its tip, and five glass cards that light as their node crosses that line, each with a year, a Done / In progress / Next / Goal tag and two key figures; nodes are pink when done, sun and pulsing for now, violet once reached); a careers list of rows that indent on hover; a CTA panel lit by a pink-to-violet radial with an email form; and a footer.

THE REACTOR
A canvas tokamak in a framed panel, aspect-ratio 1 to 0.92, sized by a ResizeObserver: 18 toroidal-field coils drawn as Princeton-D loops (a straight inner leg against the central column), split into segments and depth-sorted together with every plasma particle so each coil passes in front of and behind the ring piece by piece (opaque casings with source-over, the optically thin plasma with additive blending); casings lit warm by the plasma near its midplane, plus a soft camera bloom over everything so the near coils sit inside the glow; a central solenoid with a current pulse running up it; about 1600 plasma particles (750 under 700px wide) following helical field lines (poloidal speed = toroidal speed / q, with q rising from 1 at the core toward the edge); a divertor glow ring; and four label chips with dashed leaders. Project with a simple perspective camera, tilt and yaw it toward the pointer with easing, and spin it slowly.
Run a shot when the panel first comes into view: coils energise, breakdown, ramp-up, flat-top, with a HUD that shows the phase, a live telemetry table and a scrolling fusion-power trace, plus a "New shot" button that restarts it. Pause the loop when the panel is off screen. Under prefers-reduced-motion draw one settled frame instead of animating, skip the section reveals and the star twinkle, and keep the landscape scrub, since the reader is driving it.

THE FLOOR
One h1, a main, aria-hidden on the landscape SVG and both canvases, labels on the burger and the restart button, visible focus rings, no horizontal scroll at 390px.