:root {
  --font-sans: Pretendard, -apple-system, 'Apple SD Gothic Neo', 'Malgun Gothic', sans-serif;
  --font-mono: ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
  --white: #ffffff;
  --g90: rgba(255,255,255,0.9);
  --g70: rgba(255,255,255,0.7);
  --g50: rgba(255,255,255,0.5);
  --g30: rgba(255,255,255,0.3);
  --g15: rgba(255,255,255,0.15);
  --g08: rgba(255,255,255,0.08);
  --red: #ff4444;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html, body {
  width: 100%; height: 100%;
  background: #000;
  overflow: hidden;
  font-family: var(--font-sans);
  color: var(--white);
}

#bg-canvas {
  position: fixed; inset: 0;
  width: 100vw; height: 100vh;
  display: block;
}

#glow {
  position: fixed; inset: 0;
  pointer-events: none;
  background:
    radial-gradient(ellipse 90% 55% at 50% 118%, rgba(255,255,255,0.10), transparent 60%),
    radial-gradient(ellipse 70% 40% at 50% -12%, rgba(255,255,255,0.05), transparent 65%);
}

/* ---------- stage: 1920x1080 fixed coordinate system ---------- */
#stage {
  position: fixed;
  width: 1920px; height: 1080px;
  left: 50%; top: 50%;
  transform-origin: center center;
}

/* ---------- header ---------- */
#hdr {
  position: absolute; left: 40px; right: 40px; top: 28px;
  display: flex; justify-content: space-between; align-items: center;
  opacity: 0;
}
#hdr-brand {
  font-size: 22px; font-weight: 800; letter-spacing: 0.14em;
}
#hdr-brand span { font-weight: 300; letter-spacing: 0.06em; color: var(--g70); margin-left: 10px; }
#hdr-steps { display: flex; gap: 36px; list-style: none; }
#hdr-steps li {
  font-size: 14px; color: var(--g30); letter-spacing: 0.06em;
  padding-bottom: 6px; border-bottom: 1px solid transparent;
  transition: color .6s, border-color .6s;
}
#hdr-steps li b { font-family: var(--font-mono); font-weight: 600; margin-right: 8px; }
#hdr-steps li.active { color: var(--white); border-bottom-color: var(--g70); }
#hdr-steps li.done { color: var(--g50); }

/* ---------- panels ---------- */
#req-panel { position: absolute; left: 40px; top: 120px; width: 400px; height: 860px; }
#ds-panel  { position: absolute; left: 40px; top: 578px; width: 400px; height: 502px; }

.panel-title {
  font-size: 15px; font-weight: 700; letter-spacing: 0.22em;
  text-transform: uppercase; color: var(--g70);
  margin-bottom: 14px; opacity: 0;
}
.panel-title em { font-style: normal; font-weight: 300; color: var(--g50); margin-left: 8px; letter-spacing: 0.04em; }

#req-cards { display: flex; flex-direction: column; gap: 18px; }
.req-card {
  display: flex; gap: 14px; align-items: flex-start;
  border: 1px solid var(--g15);
  background: rgba(0,0,0,0.55);
  padding: 20px 22px;
  opacity: 0;
}
.req-card .req-id {
  font-family: var(--font-mono); font-size: 14px; font-weight: 700;
  color: var(--white);
  border: 1px solid var(--g30);
  padding: 4px 9px; flex: none; margin-top: 2px;
}
.req-card p { font-size: 19.5px; line-height: 1.5; color: var(--g90); font-weight: 400; }

/* ---------- datasheet stack ---------- */
#ds-stack {
  position: relative;
  width: 330px; height: 420px;
  margin: 28px 0 0 26px;
}
.ds-page {
  position: absolute; inset: 0;
  background: #101010;
  border: 1px solid var(--g30);
  box-shadow: 0 8px 30px rgba(0,0,0,0.8);
  opacity: 0;
}
.ds-p5 { transform: translate(40px, -26px) rotate(3.2deg);  background: #0a0a0a; }
.ds-p4 { transform: translate(30px, -19px) rotate(2.2deg);  background: #0c0c0c; }
.ds-p3 { transform: translate(20px, -13px) rotate(1.4deg);  background: #0e0e0e; }
.ds-p2 { transform: translate(10px, -6px)  rotate(0.7deg);  background: #101010; }
.ds-page img {
  width: 100%; height: 100%;
  object-fit: cover; object-position: top;
  display: block;
  filter: grayscale(1);
}
.ds-p5 img { filter: grayscale(1) brightness(0.5); }
.ds-p4 img { filter: grayscale(1) brightness(0.62); }
.ds-p3 img { filter: grayscale(1) brightness(0.74); }
.ds-p2 img { filter: grayscale(1) brightness(0.86); }
.ds-p1 { transform: none; background: #fff; overflow: hidden; }
#ds-front { width: 100%; height: 100%; object-fit: cover; object-position: top; display: block; filter: grayscale(1); }
#ds-overlay { position: absolute; inset: 0; pointer-events: none; }
#ds-label {
  margin: 10px 0 0 2px; max-width: 400px;
  font-family: var(--font-mono); font-size: 11px; line-height: 1.6;
  color: var(--g50); letter-spacing: 0.02em;
  opacity: 0;
}

/* ---------- main working area ---------- */
#main-area { position: absolute; left: 490px; top: 120px; width: 1390px; height: 880px; }
#scene2-root, #scene3-root { position: absolute; inset: 0; }
#scene3-root { pointer-events: none; }

/* ---------- BD layer ---------- */
#bd-layer {
  position: absolute; left: 40px; top: 100px; width: 1840px; height: 920px;
  opacity: 0; pointer-events: none;
}
#scene4-root { position: absolute; inset: 0; }

/* ---------- caption ---------- */
#caption {
  position: absolute; left: 0; right: 0; bottom: 26px;
  text-align: center;
}
#caption-text {
  display: inline-block;
  font-size: 17px; font-weight: 300; letter-spacing: 0.12em;
  color: var(--g70);
  opacity: 0;
}

/* ---------- replay ---------- */
#replay {
  position: absolute; right: 40px; bottom: 24px;
  font-family: var(--font-mono); font-size: 12px; letter-spacing: 0.2em;
  color: var(--g70); background: transparent;
  border: 1px solid var(--g30);
  padding: 9px 22px;
  cursor: pointer; opacity: 0; pointer-events: none;
  transition: color .3s, border-color .3s;
}
#replay:hover { color: var(--white); border-color: var(--g70); }