Train

// <TrainScene>: a steam train crossing a stone viaduct at dusk, mountains behind.
// `duration` is seconds for the train to cross the frame (default 30).

import { W, bandPath, ridgeY, seeded, type Ridge } from './geometry';
import { SceneFrame, sceneStyles as base, useSvgId, type SceneProps } from './scene';
import styles from './train-scene.module.css';

export const trainTheme = {
  skyTop: '#283a6b',
  skyMid: '#b5647f',
  skyBottom: '#f4a76f',
  sun: '#ffd9a0',
  mountain1: '#7a5a86',
  mountain2: '#563f6b',
  viaduct: '#3a2b4f',
  forest: '#241b38',
  train: '#1b1428',
  windows: '#ffd98a',
};
export type TrainTheme = typeof trainTheme;

const DECK = 470;
const FOREST: Ridge = [[10, 200], [6, 80]];

const rand = seeded(31);
const STARS = Array.from({ length: 30 }, () => ({
  x: rand() * W,
  y: 20 + rand() * 230,
  r: 0.5 + rand() * 1,
  dur: 2 + rand() * 3,
  delay: rand() * 5,
}));

// Trees along the forest ridge in front of the viaduct's piers.
const TREES = Array.from({ length: 16 }, (_, i) => {
  const x = i * 26 + rand() * 12;
  return { x, y: ridgeY(x, 640, FOREST) + 2, h: 26 + rand() * 22 };
});

// Viaduct: a solid wall with arched openings cut out (even-odd fill).
const VIADUCT = (() => {
  let d = `M-10 ${DECK} H${W + 10} V700 H-10 Z`;
  for (let x = 0; x < W; x += 50) {
    const left = x + 12, right = x + 50, r = (right - left) / 2;
    d += ` M${left} 700 V520 A${r} ${r} 0 0 1 ${right} 520 V700 Z`;
  }
  return d;
})();

const CARRIAGES = [0, 1, 2].map(k => -110 - 50 * k);

/** A steam train crossing a stone viaduct at dusk. */
export function TrainScene(props: SceneProps<TrainTheme>) {
  const sky = useSvgId('sky');
  const glow = useSvgId('glow');

  return (
    <SceneFrame
      {...props}
      defaultTheme={trainTheme}
      defaultDuration={30}
      art={
        <>
          <defs>
            <linearGradient id={sky} x1="0" y1="0" x2="0" y2="1">
              <stop offset="0" stopColor="var(--sky-top)" />
              <stop offset="0.42" stopColor="var(--sky-mid)" />
              <stop offset="0.66" stopColor="var(--sky-bottom)" />
            </linearGradient>
            <radialGradient id={glow}>
              <stop offset="0" stopColor="var(--sun)" stopOpacity="0.9" />
              <stop offset="1" stopColor="var(--sun)" stopOpacity="0" />
            </radialGradient>
          </defs>

          <rect width={W} height="700" fill={`url(#${sky})`} />

          <g fill="#fff">
            {STARS.map((s, i) => (
              <circle
                key={i}
                className={styles.star}
                cx={s.x.toFixed(1)}
                cy={s.y.toFixed(1)}
                r={s.r.toFixed(2)}
                style={{ animationDuration: `${s.dur.toFixed(2)}s`, animationDelay: `${(-s.delay).toFixed(2)}s` }}
              />
            ))}
          </g>

          <circle className={styles.glow} cx="112" cy="420" r="130" fill={`url(#${glow})`} />
          <circle cx="112" cy="420" r="34" fill="var(--sun)" />

          <path fill="var(--mountain-1)" d={bandPath(400, [[30, 400], [14, 200, 1]])} />
          <path fill="var(--mountain-2)" d={bandPath(452, [[24, 400, 2], [10, W / 3]])} />

          <g className={base.across} style={{ animationDuration: '80s', animationDelay: '-30s' }}>
            <ellipse cx="0" cy="520" rx="150" ry="10" fill="#fff" opacity="0.18" />
          </g>

          <path fill="var(--viaduct)" fillRule="evenodd" d={VIADUCT} />
          <rect x="-10" y={DECK - 3} width={W + 20} height="3" fill="var(--viaduct)" opacity="0.6" />

          {/* Train: origin at the front of the locomotive, on the deck, heading right */}
          <g className={styles.train}>
            <g fill="var(--train)">
              <rect x="-60" y="-30" width="22" height="26" rx="2" />
              <rect x="-38" y="-22" width="34" height="18" rx="3" />
              <path d="M-4 -22 L2 -16 L2 -4 L-4 -4 Z" />
              <rect x="-14" y="-33" width="6" height="11" />
              <path d="M2 -4 L8 0 L-2 0 Z" />
              {CARRIAGES.map(x => (
                <g key={x}>
                  <rect x={x - 1} y="-27" width="48" height="4" rx="2" />
                  <rect x={x} y="-24" width="46" height="20" rx="3" />
                  <rect x={x + 46} y="-10" width="4" height="3" />
                </g>
              ))}
            </g>
            <g fill="var(--windows)">
              <rect x="-55" y="-26" width="10" height="8" rx="1" />
              {CARRIAGES.flatMap(x =>
                [0, 1, 2, 3].map(j => <rect key={`${x}-${j}`} x={x + 5 + 10 * j} y="-19" width="6" height="7" rx="1" />),
              )}
            </g>
            <g fill="#120d1d">
              {[-50, -36, -20, -8].map(x => <circle key={x} cx={x} cy="-3" r="4" />)}
              {CARRIAGES.flatMap(x => [x + 8, x + 38]).map(x => <circle key={x} cx={x} cy="-3" r="3.5" />)}
            </g>
            <g transform="translate(-11 -36)" fill="#f4eef2">
              {[0, 0.8, 1.6].map(d => (
                <circle key={d} className={styles.puff} r="5" style={{ animationDelay: `${-d}s` }} />
              ))}
            </g>
          </g>

          <path fill="var(--forest)" d={bandPath(640, FOREST)} />
          <g fill="var(--forest)">
            {TREES.map((t, i) => (
              <path
                key={i}
                d={`M${t.x.toFixed(1)} ${(t.y - t.h).toFixed(1)} L${(t.x + 9).toFixed(1)} ${t.y.toFixed(1)} L${(t.x - 9).toFixed(1)} ${t.y.toFixed(1)} Z`}
              />
            ))}
          </g>
        </>
      }
    />
  );
}

.train {
  transform: translate(300px, 470px); /* resting spot for reduced motion */
  animation: run var(--duration) linear infinite;
  animation-delay: calc(var(--duration) * -0.45);
}
.puff  { animation: puff 2.4s ease-out infinite; }
.star  { animation: twinkle ease-in-out infinite alternate; }
.glow  { animation: glow 3s ease-in-out infinite alternate; }

@keyframes run {
  from { transform: translate(0px, 470px); }
  to   { transform: translate(620px, 470px); }
}
@keyframes puff {
  0%   { transform: translate(0, 0) scale(0.6); opacity: 0.85; }
  100% { transform: translate(-48px, -40px) scale(2.6); opacity: 0; }
}
@keyframes twinkle { from { opacity: 0.2; } to { opacity: 1; } }
@keyframes glow    { from { opacity: 0.75; } to { opacity: 1; } }

// Shared geometry for the scenes. Every scene draws into a portrait 400×700 viewBox.

export const W = 400;
export const H = 700;

/** One sine term of a ridge: [amplitude, wavelength, phase?]. */
export type Ridge = ReadonlyArray<readonly [amp: number, len: number, phase?: number]>;

/** Height of a ridge made of summed sines at x. */
export function ridgeY(x: number, y: number, components: Ridge): number {
  let h = y;
  for (const [amp, len, phase = 0] of components) h += amp * Math.sin((x / len) * Math.PI * 2 + phase);
  return h;
}

/**
 * A closed band 2×W wide whose edge follows ridgeY, filled toward `toward` (H = down, 0 = up).
 * Sliding it by W loops seamlessly as long as every wavelength divides W evenly.
 */
export function bandPath(y: number, components: Ridge, toward = H): string {
  let d = `M0 ${toward}`;
  for (let x = 0; x <= W * 2; x += 8) d += ` L${x} ${ridgeY(x, y, components).toFixed(1)}`;
  return `${d} L${W * 2} ${toward} Z`;
}

/** Deterministic PRNG so scattered details (stars, trees, bubbles) render identically on server and client. */
export function seeded(seed: number): () => number {
  return () => {
    seed = (seed + 0x6d2b79f5) | 0;
    let t = Math.imul(seed ^ (seed >>> 15), 1 | seed);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

import { useId, type CSSProperties, type ReactNode } from 'react';
import { H, bandPath, type Ridge } from './geometry';
import styles from './scene.module.css';

export { SceneFrame } from './scene-frame';
export { styles as sceneStyles };

/** Props every scene accepts. `T` is the scene's theme (colour tokens). */
export type SceneProps<T> = {
  /** Seconds for the scene's main crossing. */
  duration?: number;
  /** Override any of the scene's colours. */
  theme?: Partial<T>;
  /** Freeze the animation. Scenes also pause on their own while off-screen. */
  paused?: boolean;
  className?: string;
  style?: CSSProperties;
  /** Content rendered on top of the scene (headings, buttons…). */
  children?: ReactNode;
};

/** A per-instance prefix for gradient ids, so several copies of a scene can share a page. */
export function useSvgId(name: string): string {
  return `qs${useId().replace(/[^a-zA-Z0-9_-]/g, '')}${name}`;
}

export type WaveLayerProps = {
  y: number;
  components: Ridge;
  fill: string;
  /** Seconds per sideways loop; 0 keeps the band still. */
  drift?: number;
  /** Seconds per up-and-down swell; 0 disables it. */
  swell?: number;
  reverse?: boolean;
  delay?: number;
  /** Fill toward the bottom (H) or the top (0) of the scene. */
  toward?: number;
  opacity?: number;
};

/** A band of water, hills or sand that can drift sideways and swell. */
export function WaveLayer({ y, components, fill, drift = 0, swell = 0, reverse, delay = 0, toward = H, opacity }: WaveLayerProps) {
  const path = (
    <path
      className={drift ? `${styles.drift} ${reverse ? styles.reverse : ''}` : undefined}
      style={drift ? { animationDuration: `${drift}s` } : undefined}
      fill={fill}
      opacity={opacity}
      d={bandPath(y, components, toward)}
    />
  );
  if (!swell) return path;
  return (
    <g className={styles.swell} style={{ animationDuration: `${swell}s`, animationDelay: `${-delay}s` }}>
      {path}
    </g>
  );
}

'use client';

import { useEffect, useRef, useState, type CSSProperties, type ReactNode } from 'react';
import { H, W } from './geometry';
import styles from './scene.module.css';

// skyTop → --sky-top, water1 → --water-1
const toVar = (key: string) => `--${key.replace(/([A-Z])/g, '-$1').replace(/(\d+)/g, '-$1').toLowerCase()}`;

export type SceneFrameProps = {
  defaultTheme: Record<string, string>;
  defaultDuration: number;
  art: ReactNode;
  duration?: number;
  theme?: Record<string, string | undefined>;
  paused?: boolean;
  className?: string;
  style?: CSSProperties;
  children?: ReactNode;
};

/**
 * The frame shared by every scene: sizing, theming, overlay and off-screen pausing.
 * It's the only client component; the scene art itself renders on the server.
 */
export function SceneFrame({
  defaultTheme,
  defaultDuration,
  art,
  duration = defaultDuration,
  theme,
  paused,
  className,
  style,
  children,
}: SceneFrameProps) {
  const ref = useRef<HTMLDivElement>(null);
  const [offscreen, setOffscreen] = useState(false);

  useEffect(() => {
    const el = ref.current;
    if (!el) return;
    const observer = new IntersectionObserver(([entry]) => setOffscreen(!entry.isIntersecting));
    observer.observe(el);
    return () => observer.disconnect();
  }, []);

  const vars: Record<string, string> = { '--duration': `${duration}s` };
  for (const [key, value] of Object.entries({ ...defaultTheme, ...theme })) {
    if (value) vars[toVar(key)] = value;
  }

  const classes = [styles.root, (paused || offscreen) && styles.paused, className].filter(Boolean).join(' ');

  return (
    <div ref={ref} className={classes} style={{ ...vars, ...style } as CSSProperties}>
      <svg
        className={styles.art}
        viewBox={`0 0 ${W} ${H}`}
        preserveAspectRatio="xMidYMid slice"
        aria-hidden="true"
        focusable="false"
      >
        {art}
      </svg>
      {children && <div className={styles.overlay}>{children}</div>}
    </div>
  );
}

.root {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 4 / 7;
  overflow: hidden;
  contain: content;
}

.art {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.overlay {
  position: absolute;
  inset: 0;
}

/* Shared motion primitives used by every scene */
.drift   { animation: drift linear infinite; }
.reverse { animation-name: driftReverse; }
.swell   { animation: swell ease-in-out infinite alternate; }
.across  { animation: across linear infinite; }
.glint   { animation: glint ease-in-out infinite alternate; }

@keyframes drift        { to   { transform: translateX(-400px); } }
@keyframes driftReverse { from { transform: translateX(-400px); } to { transform: translateX(0); } }
@keyframes swell  { from { transform: translateY(-3px); } to { transform: translateY(3px); } }
@keyframes across { from { transform: translateX(-260px); } to { transform: translateX(660px); } }
@keyframes glint  { from { opacity: 0.25; } to { opacity: 0.85; } }

.paused * { animation-play-state: paused !important; }

@media (prefers-reduced-motion: reduce) {
  .root * { animation: none !important; }
}