<style>
    @import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;800&display=swap');

    :root {
      --cyan: #facc15;
      --cyan-dim: rgba(250, 204, 21, 0.15);
      --cyan-glow: rgba(250, 204, 21, 0.4);
      --yellow: #facc15;
      --yellow-glow: rgba(250, 204, 21, 0.45);
      --tech-bg-1: #1a1a1a;
      --tech-bg-2: #242424;
      --tech-bg-3: #2e2e2e;
      --tech-card: rgba(42, 42, 42, 0.97);
      --tech-border: rgba(255, 255, 255, 0.15);
      --tech-border-bright: rgba(250, 204, 21, 0.6);
    }

    body {
      font-family: 'Inter', sans-serif;
      background-color: var(--tech-bg-1);
      color: #ffffff;
      scroll-behavior: smooth;
      overflow-x: hidden;
    }


    /* ── Tech grid section backgrounds ── */
    .tech-section {
      background-color: var(--tech-bg-2);
      background-image:
        linear-gradient(rgba(250,204,21,0.05) 1px, transparent 1px),
        linear-gradient(90deg, rgba(250,204,21,0.05) 1px, transparent 1px);
      background-size: 64px 64px;
      position: relative;
    }
    .tech-section-alt {
      background-color: var(--tech-bg-1);
      background-image:
        linear-gradient(rgba(250,204,21,0.04) 1px, transparent 1px),
        linear-gradient(90deg, rgba(250,204,21,0.04) 1px, transparent 1px);
      background-size: 80px 80px;
      position: relative;
    }

    /* ── Corner accent decoration ── */
    .tech-corner { position: relative; }
    .tech-corner::before {
      content: '';
      position: absolute;
      top: 0; left: 0;
      width: 20px; height: 20px;
      border-top: 2px solid var(--cyan);
      border-left: 2px solid var(--cyan);
      opacity: 0.55;
      pointer-events: none;
    }
    .tech-corner::after {
      content: '';
      position: absolute;
      bottom: 0; right: 0;
      width: 20px; height: 20px;
      border-bottom: 2px solid var(--cyan);
      border-right: 2px solid var(--cyan);
      opacity: 0.55;
      pointer-events: none;
    }

    .glass-header {
      background: rgba(0, 0, 0, 0.85);
      backdrop-filter: blur(16px);
      border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    }

    .hero-gradient {
      background: radial-gradient(ellipse at 50% 60%, rgba(40,30,0,0.35) 0%, var(--tech-bg-1) 70%);
    }

    /* ── Cards ── */
    .card-hover {
      transition: all 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);
      border: 1px solid rgba(255, 255, 255, 0.15);
      background: rgba(255, 255, 255, 0.04);
    }
    .card-hover:hover {
      transform: translateY(-8px);
      border-color: var(--cyan-border-bright, var(--tech-border-bright));
      background: rgba(255, 255, 255, 0.1);
      box-shadow: 0 20px 50px -15px var(--cyan-glow), 0 0 1px var(--cyan);
    }

    /* ── Toughman vs competitor comparison cards ── */
    .toughman-advantage-card {
      background: rgba(255, 255, 255, 0.05);
      border: 1px solid rgba(250,204,21,0.3);
      border-left: 4px solid var(--cyan);
      position: relative;
      overflow: hidden;
    }
    .toughman-advantage-card::before {
      content: '';
      position: absolute;
      top: 0; left: 0; right: 0;
      height: 1px;
      background: linear-gradient(90deg, var(--cyan), transparent);
      opacity: 0.5;
    }
    .competitor-card {
      background: rgba(30, 30, 30, 0.95);
      border: 1px solid rgba(255,255,255,0.1);
      border-left: 4px solid rgba(255,255,255,0.2);
    }

    /* ── Contact form card ── */
    .contact-form-card {
      background: rgba(255, 255, 255, 0.04);
      border: 1px solid rgba(255, 255, 255, 0.15);
      position: relative;
    }
    .contact-form-card::before {
      content: '';
      position: absolute;
      top: 0; left: 0; right: 0;
      height: 1px;
      background: linear-gradient(90deg, transparent, var(--cyan), transparent);
      opacity: 0.4;
    }

    /* ── Tech page cards ── */
    .tech-page-card {
      background: rgba(255, 255, 255, 0.04);
      border: 1px solid rgba(255, 255, 255, 0.15);
      position: relative;
      overflow: hidden;
    }
    .tech-page-card::after {
      content: '';
      position: absolute;
      bottom: 0; left: 0; right: 0;
      height: 1px;
      background: linear-gradient(90deg, transparent, var(--cyan), transparent);
      opacity: 0.25;
    }

    /* ── Product page cards ── */
    .product-page-card {
      background: var(--tech-card);
      border: 1px solid var(--tech-border);
      transition: all 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);
      position: relative;
      overflow: hidden;
    }
    .product-page-card::before {
      content: '';
      position: absolute;
      top: 0; left: 0; right: 0;
      height: 1px;
      background: linear-gradient(90deg, transparent, var(--yellow), transparent);
      opacity: 0.5;
    }
    .product-page-card:hover {
      border-color: rgba(250,204,21,0.35);
      box-shadow: 0 20px 50px -15px var(--yellow-glow);
      transform: translateY(-4px);
    }

    /* ── Section label with line ── */
    .section-label {
      display: flex;
      align-items: center;
      gap: 10px;
      font-size: 0.7rem;
      font-weight: 900;
      letter-spacing: 0.4em;
      text-transform: uppercase;
      color: var(--cyan);
    }
    .section-label::before {
      content: '';
      display: inline-block;
      width: 28px; height: 1px;
      background: var(--cyan);
      box-shadow: 0 0 8px var(--cyan);
    }

    /* ── Pulsing status dot ── */
    @keyframes pulseDot {
      0%, 100% { transform: scale(1); opacity: 1; }
      50%       { transform: scale(1.9); opacity: 0.4; }
    }
    .pulse-dot {
      display: inline-block;
      width: 6px; height: 6px;
      border-radius: 50%;
      background: var(--cyan);
      box-shadow: 0 0 8px var(--cyan);
      animation: pulseDot 2s ease-in-out infinite;
    }

    /* ── Tech tag (hero badge) ── */
    .tech-tag {
      background: rgba(250, 204, 21, 0.08);
      color: var(--cyan);
      padding: 6px 20px;
      border-radius: 2px;
      font-size: 0.85rem;
      font-weight: 800;
      text-transform: uppercase;
      letter-spacing: 2px;
      border: 1px solid rgba(250,204,21,0.4);
      box-shadow: 0 0 24px rgba(250,204,21,0.18);
    }

    .hero-title {
      text-shadow: 0 10px 40px rgba(0,0,0,0.9);
    }

    /* ── Input fields ── */
    .input-field {
      background: rgba(255, 255, 255, 0.08);
      border: 1px solid rgba(250, 204, 21, 0.3);
      transition: all 0.3s ease;
      color: #ffffff;
    }
    .input-field:focus {
      border-color: var(--cyan);
      background: rgba(255, 255, 255, 0.12);
      outline: none;
      box-shadow: 0 0 15px rgba(250,204,21,0.25);
    }
    .input-field::placeholder {
      color: rgba(255,255,255,0.5);
    }

    /* ── Hero video bg ── */
    .hero-video-bg {
      position: absolute;
      inset: 0;
      opacity: 0;
      transition: opacity 2s ease-in-out;
    }
    .hero-video-bg.active { opacity: 1; }
    .hero-video-bg video {
      width: 100%; height: 100%;
      object-fit: cover;
      filter: brightness(0.92) contrast(1.1);
    }

    /* ── Tech carousel ── */
    .tech-carousel-container {
      position: relative;
      height: 600px;
      overflow: hidden;
    }
    .tech-slide {
      position: absolute;
      width: 100%;
      opacity: 0;
      transform: translateY(100%);
      transition: all 0.8s cubic-bezier(0.165, 0.84, 0.44, 1);
      pointer-events: none;
    }
    .tech-slide.active {
      opacity: 1;
      transform: translateY(0);
      pointer-events: auto;
    }
    .tech-slide.prev {
      opacity: 0;
      transform: translateY(-100%);
    }
    .tech-nav-dot {
      width: 8px; height: 8px;
      border-radius: 50%;
      background: rgba(250,204,21,0.2);
      cursor: pointer;
      transition: all 0.3s ease;
    }
    .tech-nav-dot.active {
      width: 8px; height: 32px;
      border-radius: 4px;
      background: var(--cyan);
      box-shadow: 0 0 12px var(--cyan);
    }

    @keyframes slowZoom {
      0%   { transform: scale(1); }
      100% { transform: scale(1.1); }
    }
    .animate-slow-zoom {
      animation: slowZoom 20s infinite alternate linear;
    }

    /* ── Motor animation ── */
    .motor-rotor {
      transform-origin: center;
      animation: rotateMotor 2s linear infinite;
    }
    @keyframes rotateMotor {
      from { transform: rotate(0deg); }
      to   { transform: rotate(360deg); }
    }
    .battery-level {
      animation: batteryCharge 3s ease-in-out infinite;
    }
    @keyframes batteryCharge {
      0%, 100% { width: 40px; }
      50%       { width: 106px; }
    }

    /* ── Page views ── */
    .page-view {
      display: none;
      opacity: 0;
      transform: translateY(15px);
      transition: opacity 0.5s ease, transform 0.5s ease;
    }
    .page-view.active {
      display: block;
      opacity: 1;
      transform: translateY(0);
    }

    .about-glass-card {
      background: rgba(10, 10, 10, 0.88);
      backdrop-filter: blur(12px);
      border: 1px solid rgba(255,255,255,0.1);
    }

    .big-number {
      font-size: 12rem;
      line-height: 1;
      font-weight: 800;
      color: rgba(250,204,21,0.03);
      position: absolute;
      z-index: 0;
      user-select: none;
    }

    /* ── History timeline ── */
    .history-bg-layer {
      position: absolute;
      inset: 0;
      background-size: cover;
      background-position: center;
      transition: opacity 0.8s ease, transform 1.2s ease;
      opacity: 0;
      transform: scale(1.05);
    }
    .history-bg-layer.active {
      opacity: 0.28;
      transform: scale(1);
    }
    .history-item-row {
      border-bottom: 1px solid rgba(250,204,21,0.1);
      transition: all 0.3s ease;
      cursor: pointer;
    }
    .history-item-row:hover {
      border-bottom-color: var(--cyan);
      padding-left: 1rem;
      background: rgba(250,204,21,0.03);
    }
    .history-item-row:hover .year-val { color: var(--cyan); }

    /* ── Product immersive carousel ── */
    .product-immersive-section {
      background-color: #f5f5f5;
      height: 1400px;
      position: relative;
    }
    .product-bg-layer {
      position: absolute;
      inset: 0;
      opacity: 0;
      transition: opacity 1.2s cubic-bezier(0.4, 0, 0.2, 1);
      z-index: 1;
    }
    .product-bg-layer.active { opacity: 1; }
    .product-bg-layer img {
      width: 100%; height: 100%;
      object-fit: cover;
      object-position: center;
      filter: brightness(0.85);
      transition: transform 15s linear;
    }
    .product-bg-layer.active img { transform: scale(1.1); }
    .product-content-overlay {
      position: relative;
      z-index: 10;
      height: 100%;
      display: flex;
      align-items: center;
    }
    .product-slide-info {
      display: none;
      opacity: 0;
      transform: translateX(-30px);
      transition: all 0.8s cubic-bezier(0.22, 1, 0.36, 1);
    }
    .product-slide-info.active {
      display: block;
      opacity: 1;
      transform: translateX(0);
    }
    .spec-animate-item {
      transform: translateX(-20px);
      opacity: 0;
      transition: all 0.6s ease;
    }
    .product-slide-info.active .spec-animate-item {
      transform: translateX(0);
      opacity: 1;
    }
    .delay-100 { transition-delay: 0.1s; }
    .delay-200 { transition-delay: 0.2s; }
    .delay-300 { transition-delay: 0.3s; }

    /* ── Vertical nav ── */
    .vertical-nav {
      position: absolute;
      right: 48px;
      top: 50%;
      transform: translateY(-50%);
      z-index: 50;
      display: flex;
      flex-direction: column;
      gap: 24px;
    }
    .nav-progress-bar {
      width: 2px;
      height: 60px;
      background: rgba(250,204,21,0.1);
      position: relative;
      margin: 0 auto;
    }
    .nav-progress-fill {
      position: absolute;
      top: 0; left: 0;
      width: 100%;
      background: var(--cyan);
      height: 0%;
      transition: height 5s linear;
      box-shadow: 0 0 8px var(--cyan);
    }
    .nav-item.active .nav-progress-fill { height: 100%; }
    .nav-num {
      font-size: 10px;
      font-weight: 900;
      color: rgba(255,255,255,0.3);
      transition: color 0.3s;
      cursor: pointer;
    }
    .nav-item.active .nav-num {
      color: var(--cyan);
    }

    /* ── Language toggle ── */
    .lang-btn {
      display: flex;
      align-items: center;
      gap: 4px;
      padding: 6px 14px;
      border: 1px solid rgba(255,255,255,0.2);
      font-size: 11px;
      font-weight: 800;
      letter-spacing: 0.1em;
      text-transform: uppercase;
      cursor: pointer;
      transition: all 0.3s ease;
      background: transparent;
      color: rgba(255,255,255,0.6);
    }
    .lang-btn:hover {
      border-color: #facc15;
      color: #facc15;
    }
    .lang-btn .lang-opt { transition: all 0.2s; }
    .lang-btn .lang-opt.active { color: #facc15; }
    .lang-divider { color: rgba(255,255,255,0.2); font-size: 10px; }

    /* ── Hide/show elements by language ── */
    [data-lang="en"] { display: none; }
    body.lang-en [data-lang="zh"] { display: none; }
    body.lang-en [data-lang="en"] { display: revert; }

    /* ── Wheel rotation animation ── */
    .wheel-rotate {
      transform-origin: center;
      animation: wheelSpin 2s linear infinite;
    }
    @keyframes wheelSpin {
      from { transform: rotate(0deg); }
      to { transform: rotate(360deg); }
    }

    /* ── AWD Video Carousel ── */
    .awd-video {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      opacity: 0;
      visibility: hidden;
      transition: opacity 2s ease-in-out, visibility 0s 2s;
    }
    .awd-video.active {
      opacity: 0.6;
      visibility: visible;
      transition: opacity 2s ease-in-out, visibility 0s 0s;
    }
  </style>