/* Accepted AI filament material, approved tricolor AI and white wordmark. */
#intro-stage {
  position: fixed;
  inset: 0 auto auto 0;
  width: var(--viewport-width, 100vw);
  height: var(--viewport-height, 100dvh);
  box-sizing: border-box;
  padding: var(--safe-top, 0px) var(--safe-right, 0px) var(--safe-bottom, 0px) var(--safe-left, 0px);
  overflow: hidden;
  background: #000;
  color: #fff;
  z-index: 100;
  isolation: isolate;
  touch-action: manipulation;
}

#intro-stage[hidden], #skip-intro[hidden] { display: none !important; }

body.intro-active #brand-link {
  z-index: 110;
  transform: none;
  will-change: auto;
  pointer-events: none;
  transition: none !important;
}

/* V / I / D and the remaining paths reveal only through opacity.
   Their approved SVG geometry, colors, letter spacing and transforms stay intact. */
body.intro-active #brand-svg path { transition: none !important; }

#concept-frame {
  position: absolute;
  left: 50%;
  top: 48.5%;
  transform: translate(-50%, -50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--intro-copy-gap, 32px);
  width: min(88%, 700px);
  max-height: calc(100% - 112px - var(--safe-top, 0px) - var(--safe-bottom, 0px));
  text-align: center;
  pointer-events: none;
}

#stroke-mount {
  display: flex;
  align-items: center;
  justify-content: center;
  flex: none;
  width: 230px;
  height: 180px;
  opacity: 0;
  transform-origin: 50% 50%;
  will-change: opacity, transform;
}

#stroke-mount > picture {
  display: block;
  width: 100%;
  height: 100%;
}

#stroke-mount img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
  pointer-events: none;
  user-select: none;
  -webkit-user-select: none;
}

#concept-copy {
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
  gap: clamp(10px, 1.2vw, 18px);
  width: 100%;
  white-space: nowrap;
  opacity: 0;
  will-change: opacity;
}

#concept-copy > * { margin: 0; }

#concept-keyword {
  font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  font-size: clamp(18px, 2.2vw, 27px);
  font-weight: 400;
  line-height: 1.3;
  letter-spacing: .075em;
  white-space: nowrap;
}

#concept-divider {
  font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  font-size: clamp(16px, 1.8vw, 23px);
  font-weight: 300;
  line-height: 1.3;
  color: rgba(255, 255, 255, .42);
}

#concept-zh {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Heiti SC", "Microsoft YaHei", sans-serif;
  font-size: clamp(15px, 1.8vw, 21px);
  font-weight: 400;
  line-height: 1.3;
  letter-spacing: .12em;
  color: rgba(255, 255, 255, .74);
}

#assembly-mount {
  position: absolute;
  left: 0;
  top: 0;
  transform-origin: 0 0;
  pointer-events: none;
  visibility: hidden;
  will-change: opacity;
}

#assembly-mount svg {
  display: block;
  width: 100%;
  height: 100%;
  overflow: visible;
}

#intro-ai-texture, #intro-ai-official {
  position: absolute;
  inset: 0;
  pointer-events: none;
  will-change: opacity;
}

.intro-convergence-light {
  position: absolute;
  display: block;
  transform-origin: 50% 50%;
  will-change: transform, opacity;
}

#skip-intro {
  position: fixed;
  bottom: calc(var(--safe-bottom, 0px) + 20px);
  left: calc(var(--viewport-width, 100vw) / 2);
  transform: translateX(-50%);
  z-index: 120;
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 64px;
  min-height: 44px;
  padding: 0 12px;
  border: 0;
  border-radius: 0;
  background: transparent;
  color: rgba(255, 255, 255, .45);
  font: 300 23px/1 -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  letter-spacing: .10em;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  transition: color 160ms ease;
}

#skip-intro:hover { color: #fff; }
#skip-intro:focus-visible { outline: 1px solid #fff; outline-offset: 4px; color: #fff; }

@media (max-height: 480px) {
  #concept-frame { gap: 16px; top: 46%; }
  #concept-copy { gap: 10px; }
  #concept-keyword { font-size: 18px; }
  #concept-zh { font-size: 14px; line-height: 1.35; }
  #concept-divider { font-size: 16px; }
  #skip-intro { bottom: calc(var(--safe-bottom, 0px) + 8px); }
}

@media (max-width: 360px) {
  #concept-keyword { font-size: 16px; letter-spacing: .045em; }
  #concept-zh { font-size: 13px; letter-spacing: .08em; }
  #concept-copy { gap: 8px; }
}

@media (prefers-reduced-motion: reduce) {
  #skip-intro { transition: none; }
}