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

:root {
  --sky-blue: #7dd3fc;
  --sky-deep: #0284c7;
  --strato-blue: #1e3a8a;
  --meso-violet: #1e1b4b;
  --thermo-dark: #0b0a2a;
  --space-black: #02021a;
  --void: #000005;
  --ink: #e8f3ff;
  --muted: #a8c2d9;
  --line: rgba(210, 232, 255, 0.28);
  --panel: rgba(3, 14, 36, 0.72);
  --accent: #fde68a;
  --coral: #f0abfc;
}

html {
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: var(--ink);
  background: var(--void);
}

.back-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 30;
  padding: 0.7rem 1.5rem;
  background: rgba(2, 2, 26, 0.42);
  border-bottom: 1px solid rgba(210, 232, 255, 0.16);
  backdrop-filter: blur(10px);
}

.back-link,
.restart-link {
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 700;
  text-decoration: none;
  transition: color 0.2s ease;
}

.back-link:hover,
.restart-link:hover {
  color: var(--ink);
}

.altitude-panel {
  position: fixed;
  right: 1.25rem;
  top: 4.2rem;
  z-index: 20;
  width: min(13rem, calc(100vw - 2rem));
  padding: 0.9rem;
  background: var(--panel);
  border: 1px solid rgba(210, 232, 255, 0.18);
  border-radius: 0.5rem;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.32);
  backdrop-filter: blur(14px);
}

.altitude-panel__label {
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.altitude-panel__value {
  margin-top: 0.2rem;
  font-size: clamp(1.7rem, 7vw, 2.5rem);
  font-weight: 900;
  line-height: 1;
  font-variant-numeric: tabular-nums;
}

.altitude-unit {
  font-size: 0.55em;
  color: var(--muted);
  font-weight: 700;
  margin-left: 0.15em;
}

.altitude-panel__zone {
  margin-top: 0.35rem;
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 800;
}

.altitude-meter {
  height: 6px;
  margin-top: 0.8rem;
  overflow: hidden;
  background: rgba(232, 247, 255, 0.12);
  border-radius: 999px;
}

.altitude-meter span {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--sky-blue), var(--accent), var(--coral));
  border-radius: inherit;
}

.altitude-panel__hint {
  margin-top: 0.55rem;
  font-size: 0.68rem;
  color: var(--muted);
  letter-spacing: 0.06em;
  text-align: right;
}

/* ── Orbit (top of document, finale) ── */
.orbit {
  min-height: 100vh;
  display: grid;
  place-items: center;
  align-content: center;
  gap: 1rem;
  padding: 5rem 1.5rem;
  text-align: center;
  position: relative;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 50%, rgba(253, 230, 138, 0.06), transparent 22rem),
    radial-gradient(circle at 20% 80%, rgba(125, 211, 252, 0.06), transparent 18rem),
    radial-gradient(circle at 80% 20%, rgba(240, 171, 252, 0.06), transparent 18rem),
    linear-gradient(180deg, var(--void) 0%, var(--space-black) 100%);
}

.orbit::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(2px 2px at 8% 18%, #fff, transparent),
    radial-gradient(1.5px 1.5px at 18% 42%, #fff, transparent),
    radial-gradient(2px 2px at 28% 8%, #fff, transparent),
    radial-gradient(1px 1px at 38% 68%, #fff, transparent),
    radial-gradient(2px 2px at 48% 28%, #fff, transparent),
    radial-gradient(1.5px 1.5px at 58% 78%, #fff, transparent),
    radial-gradient(1px 1px at 68% 12%, #fff, transparent),
    radial-gradient(2px 2px at 78% 52%, #fff, transparent),
    radial-gradient(1px 1px at 88% 32%, #fff, transparent),
    radial-gradient(2px 2px at 95% 65%, #fff, transparent),
    radial-gradient(1px 1px at 12% 88%, #fff, transparent),
    radial-gradient(1.5px 1.5px at 42% 92%, #fff, transparent),
    radial-gradient(1px 1px at 72% 95%, #fff, transparent);
  pointer-events: none;
  opacity: 0.95;
}

.orbit::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    radial-gradient(2px 2px at 22% 62%, rgba(255,255,255,.7), transparent),
    radial-gradient(1.5px 1.5px at 62% 22%, rgba(255,255,255,.7), transparent),
    radial-gradient(2px 2px at 82% 88%, rgba(255,255,255,.7), transparent),
    radial-gradient(1px 1px at 32% 38%, rgba(255,255,255,.5), transparent),
    radial-gradient(1.5px 1.5px at 92% 8%, rgba(255,255,255,.5), transparent);
  pointer-events: none;
  animation: twinkle 4s ease-in-out infinite;
}

.orbit__mark {
  position: relative;
  color: var(--coral);
  font-size: 0.9rem;
  font-weight: 900;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.orbit h2 {
  position: relative;
  font-size: clamp(2.4rem, 9vw, 5.6rem);
  line-height: 0.95;
  text-shadow: 0 4px 40px rgba(240, 171, 252, 0.35);
}

.orbit p {
  position: relative;
  max-width: 620px;
  color: var(--muted);
  font-size: clamp(1rem, 2.5vw, 1.2rem);
  line-height: 1.65;
}

.orbit .restart-link {
  position: relative;
  margin-top: 1rem;
  display: inline-block;
  padding: 0.55rem 1.2rem;
  border: 1px solid rgba(210, 232, 255, 0.3);
  border-radius: 0.5rem;
}

/* ── Ascent (REVERSED gradient: top = space, bottom = sky) ── */
.ascent {
  position: relative;
  min-height: 14000px;
  padding: 4rem 1rem 7rem;
  background:
    linear-gradient(180deg,
      var(--void) 0%,
      var(--space-black) 18%,
      var(--thermo-dark) 38%,
      var(--meso-violet) 60%,
      var(--strato-blue) 84%,
      var(--sky-deep) 100%);
}

.ascent::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 30% 6%, rgba(255, 255, 255, 0.14), transparent 24rem),
    radial-gradient(circle at 75% 32%, rgba(125, 211, 252, 0.1), transparent 30rem),
    radial-gradient(circle at 40% 76%, rgba(240, 171, 252, 0.06), transparent 22rem),
    radial-gradient(circle at 70% 90%, rgba(255, 235, 130, 0.18), transparent 28rem);
  pointer-events: none;
}

/* Sun glow at low altitudes (bottom of ascent) */
.ascent::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 70vw;
  height: 50vh;
  background: radial-gradient(ellipse at 50% 100%,
    rgba(255, 235, 130, 0.5) 0%,
    rgba(255, 200, 100, 0.3) 25%,
    rgba(255, 150, 80, 0.15) 50%,
    transparent 75%);
  pointer-events: none;
}

.cable-line {
  position: sticky;
  top: 0;
  width: 2px;
  height: 100vh;
  margin: 0 auto;
  background: linear-gradient(180deg, transparent, var(--line), transparent);
  pointer-events: none;
}

.stars {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.star {
  position: absolute;
  background: #f8fafc;
  border-radius: 50%;
  animation: twinkle 4s ease-in-out infinite;
  box-shadow: 0 0 4px rgba(255, 255, 255, 0.6);
}

@keyframes twinkle {
  0%, 100% { opacity: 0.3; transform: scale(1); }
  50% { opacity: 0.95; transform: scale(1.4); }
}

/* ── Cloud layers (positioned via JS as % of ascent height) ── */
.bg-cloud {
  position: absolute;
  pointer-events: none;
  animation: drift 60s linear infinite;
}

@keyframes drift {
  from { transform: translateX(0); }
  to { transform: translateX(50px); }
}

.bg-cloud--cumulus {
  width: 120px;
  height: 60px;
  background:
    radial-gradient(40px 25px at 30px 35px, #f1f5f9 60%, #cbd5e1 80%, transparent 90%),
    radial-gradient(50px 30px at 60px 30px, #ffffff 60%, #cbd5e1 80%, transparent 90%),
    radial-gradient(40px 25px at 90px 35px, #f1f5f9 60%, #cbd5e1 80%, transparent 90%),
    radial-gradient(60px 20px at 50px 45px, #f8fafc 50%, #cbd5e1 70%, transparent 90%);
  filter: blur(0.5px);
  opacity: 0.7;
}

.bg-cloud--cirrus {
  width: 180px;
  height: 30px;
  background:
    radial-gradient(80px 8px at 50% 50%, rgba(232, 247, 255, 0.65) 40%, transparent 70%),
    radial-gradient(50px 5px at 30% 60%, rgba(232, 247, 255, 0.45) 40%, transparent 70%),
    radial-gradient(60px 6px at 70% 40%, rgba(232, 247, 255, 0.55) 40%, transparent 70%);
  filter: blur(1.5px);
  opacity: 0.55;
}

.bg-cloud--wispy {
  width: 140px;
  height: 24px;
  background:
    radial-gradient(60px 6px at 50% 50%, rgba(165, 243, 252, 0.45) 40%, transparent 70%),
    radial-gradient(40px 4px at 30% 60%, rgba(165, 243, 252, 0.35) 40%, transparent 70%);
  filter: blur(2px);
  opacity: 0.5;
}

/* ── Aurora curtains (positioned at high altitudes = top of ascent) ── */
.bg-aurora {
  position: absolute;
  width: 35%;
  height: 18%;
  pointer-events: none;
  background:
    linear-gradient(180deg,
      transparent 0%,
      rgba(16, 185, 129, 0.55) 30%,
      rgba(34, 211, 238, 0.45) 55%,
      rgba(168, 85, 247, 0.25) 75%,
      transparent 100%);
  filter: blur(8px);
  border-radius: 50%;
  transform-origin: center top;
  animation: aurora-flow 12s ease-in-out infinite;
  mix-blend-mode: screen;
}

@keyframes aurora-flow {
  0%, 100% { transform: scaleY(1) skewX(0deg); opacity: 0.7; }
  50% { transform: scaleY(1.2) skewX(-4deg); opacity: 0.95; }
}

/* ── Earth horizon curve (at very top of ascent, very high altitude) ── */
.bg-horizon {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 200vw;
  height: 240px;
  margin-top: -120px;
  border-radius: 50%;
  background:
    radial-gradient(ellipse at 50% 100%, rgba(125, 211, 252, 0.18) 0%, transparent 50%),
    linear-gradient(180deg, transparent 0%, transparent 55%, rgba(2, 132, 199, 0.6) 75%, rgba(12, 74, 110, 0.85) 100%);
  pointer-events: none;
  box-shadow: 0 0 60px rgba(125, 211, 252, 0.25) inset;
}

.bg-horizon::before {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 12px;
  background: radial-gradient(ellipse at 50% 100%, rgba(165, 243, 252, 0.6) 0%, transparent 60%);
  filter: blur(3px);
}

.marker-list {
  position: absolute;
  inset: 0;
  max-width: 1080px;
  margin: 0 auto;
  left: 50%;
  width: min(100%, 1080px);
  transform: translateX(-50%);
  z-index: 2;
}

.zone-marker,
.marker {
  position: absolute;
  left: 1rem;
  right: 1rem;
}

.zone-marker {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  color: rgba(232, 247, 255, 0.78);
  font-size: clamp(1rem, 3vw, 1.35rem);
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  z-index: 3;
}

.zone-marker::before,
.zone-marker::after {
  content: "";
  height: 1px;
  flex: 1;
  background: rgba(232, 247, 255, 0.2);
}

.marker {
  display: grid;
  grid-template-columns: 11rem minmax(0, 22rem);
  gap: 1rem;
  width: min(100% - 2rem, 36rem);
  align-items: center;
  opacity: 0;
  transform: translateY(2rem);
  transition: opacity 0.55s ease, transform 0.55s ease;
  z-index: 3;
}

.marker.is-visible {
  opacity: 1;
  transform: translateY(0);
}

.marker:nth-of-type(even) {
  margin-left: auto;
  grid-template-columns: minmax(0, 22rem) 11rem;
}

.marker:nth-of-type(even) .marker-art {
  order: 2;
}

.marker-card {
  padding: 0.9rem 1rem;
  background: rgba(3, 14, 36, 0.66);
  border: 1px solid rgba(210, 232, 255, 0.16);
  border-radius: 0.5rem;
  box-shadow: 0 20px 55px rgba(0, 0, 0, 0.32);
  backdrop-filter: blur(10px);
}

.marker-altitude {
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 900;
  font-variant-numeric: tabular-nums;
}

.marker-card h2 {
  margin-top: 0.2rem;
  font-size: clamp(1.15rem, 4vw, 1.65rem);
  line-height: 1.12;
  letter-spacing: 0;
}

.marker-card p {
  margin-top: 0.45rem;
  color: var(--muted);
  font-size: 0.88rem;
  line-height: 1.55;
}

.marker-art {
  width: 100%;
  aspect-ratio: 1;
  display: grid;
  place-items: center;
  filter: drop-shadow(0 18px 24px rgba(0, 0, 0, 0.45));
}

.marker-art svg {
  width: 100%;
  height: 100%;
  overflow: visible;
}

/* ── Sky hero (bottom of document, start point) ── */
.sky-hero {
  min-height: 100vh;
  display: grid;
  place-items: center;
  align-content: center;
  gap: 1rem;
  padding: 7rem 1.5rem 4rem;
  text-align: center;
  position: relative;
  overflow: hidden;
  background:
    radial-gradient(ellipse at 80% 20%, rgba(255, 235, 130, 0.7) 0%, rgba(255, 200, 100, 0.4) 15%, transparent 35%),
    radial-gradient(ellipse at 50% 100%, rgba(125, 211, 252, 0.5) 0%, transparent 50%),
    linear-gradient(180deg, #1e3a8a 0%, #0284c7 28%, #38bdf8 56%, #7dd3fc 80%, #b3e5fc 100%);
}

.sky-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 22% 18%, rgba(255, 255, 255, 0.55), transparent 22rem),
    radial-gradient(circle at 78% 26%, rgba(255, 235, 130, 0.5), transparent 18rem),
    radial-gradient(circle at 50% 90%, rgba(30, 58, 138, 0.4), transparent 30rem);
  pointer-events: none;
}

.sky-hero::after {
  content: "";
  position: absolute;
  bottom: 8rem;
  left: 0;
  right: 0;
  height: 80px;
  opacity: 0.55;
  background:
    radial-gradient(160px 50px at 80px 56px, transparent 60px, rgba(255, 255, 255, 0.95) 61px, transparent 63px) repeat-x,
    radial-gradient(120px 36px at 200px 64px, transparent 44px, rgba(255, 255, 255, 0.85) 45px, transparent 47px) repeat-x;
  background-size: 280px 80px, 240px 70px;
  pointer-events: none;
}

.cloud-line {
  position: absolute;
  bottom: 8rem;
  left: 0;
  right: 0;
  height: 60px;
  opacity: 0.5;
  background:
    radial-gradient(120px 36px at 60px 42px, transparent 44px, rgba(255, 255, 255, 0.95) 45px, transparent 47px) repeat-x;
  background-size: 120px 60px;
}

.eyebrow {
  position: relative;
  color: #1e293b;
  font-size: 0.78rem;
  font-weight: 900;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.sky-hero h1 {
  position: relative;
  color: #0b1e3a;
  font-size: clamp(3rem, 12vw, 8rem);
  font-weight: 950;
  letter-spacing: 0;
  line-height: 0.95;
  text-shadow: 0 4px 30px rgba(255, 255, 255, 0.5);
}

.sky-hero p {
  position: relative;
  max-width: 620px;
  color: #143055;
  font-size: clamp(1rem, 2.4vw, 1.25rem);
  font-weight: 650;
  line-height: 1.55;
}

.scroll-cue {
  position: relative;
  margin-top: 1rem;
  color: #143055;
  font-size: 0.85rem;
  font-weight: 900;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-6px); }
}

@media (max-width: 760px) {
  .altitude-panel {
    top: auto;
    right: 0.75rem;
    bottom: 0.75rem;
    width: calc(100vw - 1.5rem);
  }

  .ascent {
    min-height: 15500px;
  }

  .marker,
  .marker:nth-of-type(even) {
    grid-template-columns: 7.5rem minmax(0, 1fr);
    width: calc(100% - 1rem);
  }

  .marker:nth-of-type(even) .marker-art {
    order: 0;
  }

  .marker-card {
    padding: 0.75rem;
  }

  .marker-card p {
    font-size: 0.8rem;
  }

  .bg-cloud--cumulus { width: 80px; height: 40px; }
  .bg-cloud--cirrus { width: 120px; height: 20px; }
  .bg-cloud--wispy { width: 100px; height: 18px; }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .marker,
  .back-link,
  .restart-link {
    transition: none;
  }

  .star,
  .scroll-cue,
  .bg-cloud,
  .bg-aurora,
  .orbit::after {
    animation: none;
  }
}