:root {
  /* Design typography source: Space Grotesk and IBM Plex Mono are (Google Fonts). Interaction (3% frequency): depth gauge is the only navigation affordance. */
  --surface-light: #e8f0f4;
  --surface-medium: #0a3d5c;
  --surface-dark: #061620;
  --surface-abyss: #020810;
  --accent-primary: #48cae4;
  --accent-secondary: #00e5cc;
  --accent-tertiary: #0077b6;
  --text-light: #c8dae4;
  --ink: #1a2a38;
  --body-bg: #e8f0f4;
  --progress: 0%;
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100%;
  background: var(--body-bg);
  color: rgba(232, 240, 244, 0.85);
  font-family: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: clamp(0.875rem, 1.1vw, 1.05rem);
  font-weight: 300;
  line-height: 1.78;
  transition: background-color 120ms linear;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(circle at 50% -10%, rgba(72, 202, 228, 0.25), transparent 35%),
    linear-gradient(180deg, rgba(232, 240, 244, 0.18), transparent 28%, rgba(2, 8, 16, 0.32));
  mix-blend-mode: screen;
  opacity: 0.75;
  z-index: 0;
}

a {
  color: var(--accent-primary);
  text-decoration: none;
}

.descent {
  position: relative;
  z-index: 1;
}

.zone {
  position: relative;
  min-height: 135vh;
  padding: 18vh 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  isolation: isolate;
}

.zone-epipelagic {
  min-height: 112vh;
  color: var(--ink);
}

.zone-mesopelagic {
  min-height: 165vh;
}

.zone-bathypelagic {
  min-height: 210vh;
  overflow: hidden;
}

.zone-hadal {
  min-height: 125vh;
  overflow: hidden;
}

.depth-gauge {
  position: fixed;
  top: 28px;
  bottom: 28px;
  left: 32px;
  width: 92px;
  z-index: 20;
  pointer-events: none;
  font-family: "Space Grotesk", "Inter", system-ui, sans-serif;
}

.gauge-track,
.gauge-fill {
  position: absolute;
  left: 0;
  top: 0;
  width: 2px;
  border-radius: 0;
}

.gauge-track {
  bottom: 0;
  background: rgba(72, 202, 228, 0.3);
}

.gauge-fill {
  height: var(--progress);
  background: var(--accent-primary);
  box-shadow: 0 0 18px rgba(72, 202, 228, 0.45);
}

.gauge-tick {
  position: absolute;
  left: 0;
  width: 14px;
  height: 1px;
  background: rgba(72, 202, 228, 0.75);
}

.gauge-tick span {
  position: absolute;
  left: 20px;
  top: -0.65rem;
  color: var(--accent-primary);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  white-space: nowrap;
}

.tick-200 { top: 25%; }
.tick-1000 { top: 58%; }
.tick-4000 { top: 85%; }

.gauge-label {
  position: absolute;
  left: -20px;
  bottom: -2px;
  color: rgba(72, 202, 228, 0.65);
  font-size: 0.65rem;
  font-weight: 500;
  letter-spacing: 0.18em;
  transform: rotate(-90deg);
  transform-origin: left bottom;
}

.opening-dossier {
  width: min(760px, calc(100vw - 48px));
  text-align: center;
  margin-left: 42px;
}

.surface-seal {
  position: absolute;
  width: min(52vw, 520px);
  aspect-ratio: 1;
  border: 1px solid rgba(0, 119, 182, 0.16);
  box-shadow: inset 0 0 0 1px rgba(72, 202, 228, 0.12), 0 0 90px rgba(72, 202, 228, 0.18);
  transform: rotate(45deg);
}

.surface-seal::before,
.surface-seal::after {
  content: "";
  position: absolute;
  inset: 11%;
  border: 1px solid rgba(0, 119, 182, 0.12);
}

.surface-seal::after {
  inset: 23%;
}

.depth-label,
.card-label {
  margin: 0 0 18px;
  color: var(--accent-primary);
  font-family: "Space Grotesk", "Inter", system-ui, sans-serif;
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  line-height: 1.35;
  text-transform: uppercase;
}

.logotype,
.diplomatic-card h2,
.hadal-panel h2 {
  position: relative;
  display: inline-block;
  margin: 0;
  font-family: "Space Grotesk", "Inter", system-ui, sans-serif;
  font-size: clamp(2rem, 5vw, 4.5rem);
  font-weight: 700;
  letter-spacing: 0.04em;
  line-height: 1.05;
  text-transform: uppercase;
}

.logotype {
  color: var(--surface-dark);
}

.diplomatic-card h2,
.hadal-panel h2 {
  color: var(--surface-light);
  font-weight: 500;
  font-size: clamp(1.75rem, 4.2vw, 3.2rem);
}

.intro-cable {
  min-height: 4.5em;
  margin: 34px auto 0;
  max-width: 680px;
  color: var(--ink);
  font-weight: 300;
}

.intro-cable::after {
  content: "";
  display: inline-block;
  width: 0.55em;
  height: 1.15em;
  margin-left: 0.18em;
  vertical-align: -0.15em;
  background: var(--accent-secondary);
  animation: cursorPulse 1.1s steps(1) infinite;
}

@keyframes cursorPulse {
  50% { opacity: 0; }
}

.reading-column {
  width: min(680px, calc(100vw - 48px));
  margin-left: 42px;
}

.cascade {
  display: flex;
  flex-direction: column;
  gap: 17vh;
}

.diplomatic-card {
  position: relative;
  width: min(100%, 600px);
  padding: clamp(28px, 4.5vw, 46px);
  background: rgba(6, 22, 32, 0.45);
  backdrop-filter: blur(16px) saturate(1.2);
  -webkit-backdrop-filter: blur(16px) saturate(1.2);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 2px;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3), inset 0 1px 0 rgba(255, 255, 255, 0.05);
}

.diplomatic-card.left {
  align-self: flex-start;
  transform: translateX(-40px);
}

.diplomatic-card.right {
  align-self: flex-end;
  transform: translateX(40px);
}

.diplomatic-card p:not(.card-label) {
  margin: 24px 0 0;
  color: rgba(232, 240, 244, 0.85);
  font-weight: 300;
}

.luminous::before {
  content: "";
  position: absolute;
  inset: -1px;
  z-index: -1;
  border-radius: 2px;
  background: linear-gradient(120deg, #00e5cc, #0077b6, #48cae4, #00e5cc);
  background-size: 300% 300%;
  opacity: 0.82;
  animation: borderCycle 3.333s linear infinite;
}

.luminous::after {
  content: "";
  position: absolute;
  inset: 1px;
  z-index: -1;
  background: rgba(6, 22, 32, 0.72);
  border-radius: 1px;
}

@keyframes borderCycle {
  to { background-position: 300% 0; }
}

.underline-draw {
  position: relative;
}

.underline-draw::after {
  content: "";
  position: absolute;
  bottom: -6px;
  left: 0;
  width: 100%;
  height: 2px;
  background: #00e5cc;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.6s cubic-bezier(0.16, 1, 0.3, 1);
}

.underline-draw.visible::after,
.underline-draw:hover::after {
  transform: scaleX(1);
}

.reveal {
  opacity: 0;
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1), transform 0.8s cubic-bezier(0.16, 1, 0.3, 1), backdrop-filter 0.8s cubic-bezier(0.16, 1, 0.3, 1);
  transform: translateY(40px);
}

.reveal.left {
  transform: translate(-40px, 40px);
}

.reveal.right {
  transform: translate(40px, 40px);
}

.reveal.visible,
.reveal.left.visible,
.reveal.right.visible {
  opacity: 1;
  transform: translate(0, 0);
}

.botanical {
  position: absolute;
  z-index: -1;
  pointer-events: none;
  opacity: 0.82;
}

.botanical path {
  stroke: #00e5cc;
  stroke-width: 1.5px;
  vector-effect: non-scaling-stroke;
  stroke-linecap: round;
  stroke-linejoin: round;
  filter: drop-shadow(0 0 7px rgba(0, 229, 204, 0.35));
}

.botanical-kelp {
  left: max(-26px, calc(50% - 520px));
  top: 10%;
  width: 180px;
  height: 620px;
}

.botanical-fan {
  right: max(-120px, calc(50% - 610px));
  bottom: 6%;
  width: 360px;
  height: 420px;
}

.particle-field {
  position: absolute;
  left: 50%;
  top: 100%;
  width: 2px;
  height: 2px;
  border-radius: 50%;
  background: rgba(72, 202, 228, 0.4);
  animation: particleDrift 30s linear infinite;
  box-shadow:
    -45vw -10vh 0 0 rgba(72,202,228,0.18), -37vw -31vh 0 1px rgba(72,202,228,0.12), -25vw -74vh 0 0 rgba(0,229,204,0.22), -18vw -52vh 0 1px rgba(72,202,228,0.16), -8vw -18vh 0 0 rgba(72,202,228,0.32),
    7vw -38vh 0 1px rgba(0,229,204,0.18), 14vw -67vh 0 0 rgba(72,202,228,0.25), 29vw -21vh 0 1px rgba(72,202,228,0.12), 42vw -81vh 0 0 rgba(0,119,182,0.22), 48vw -44vh 0 1px rgba(72,202,228,0.2),
    -49vw -112vh 0 0 rgba(72,202,228,0.2), -39vw -141vh 0 1px rgba(0,229,204,0.16), -30vw -96vh 0 0 rgba(72,202,228,0.28), -20vw -158vh 0 1px rgba(72,202,228,0.1), -11vw -126vh 0 0 rgba(0,229,204,0.2),
    4vw -104vh 0 1px rgba(72,202,228,0.2), 17vw -151vh 0 0 rgba(0,119,182,0.24), 26vw -119vh 0 1px rgba(72,202,228,0.14), 35vw -176vh 0 0 rgba(72,202,228,0.3), 44vw -132vh 0 1px rgba(0,229,204,0.18),
    -43vw -204vh 0 1px rgba(72,202,228,0.14), -33vw -230vh 0 0 rgba(0,229,204,0.24), -24vw -188vh 0 1px rgba(72,202,228,0.18), -13vw -252vh 0 0 rgba(72,202,228,0.26), -2vw -215vh 0 1px rgba(0,119,182,0.2),
    10vw -198vh 0 0 rgba(72,202,228,0.3), 21vw -246vh 0 1px rgba(0,229,204,0.14), 31vw -208vh 0 0 rgba(72,202,228,0.18), 41vw -263vh 0 1px rgba(72,202,228,0.16), 49vw -224vh 0 0 rgba(0,229,204,0.24);
}

.particles-deep {
  opacity: 1;
  filter: blur(0.1px);
  animation-duration: 36s;
}

@keyframes particleDrift {
  from { transform: translate3d(0, 0, 0); }
  to { transform: translate3d(0, -200px, 0); }
}

.hadal-panel {
  width: min(760px, calc(100vw - 48px));
  margin-left: 42px;
  text-align: left;
  padding: clamp(34px, 6vw, 70px);
}

.transmission {
  display: inline-block;
  margin-top: 32px;
  font-family: "Space Grotesk", "Inter", system-ui, sans-serif;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

@media (max-width: 760px) {
  .depth-gauge {
    left: 15px;
    width: 54px;
  }

  .gauge-tick span,
  .gauge-label {
    font-size: 0.58rem;
  }

  .opening-dossier,
  .reading-column,
  .hadal-panel {
    margin-left: 28px;
    width: calc(100vw - 64px);
  }

  .zone {
    padding-left: 18px;
    padding-right: 18px;
  }

  .diplomatic-card.left,
  .diplomatic-card.right {
    align-self: center;
  }

  .botanical-kelp {
    left: -82px;
    opacity: 0.5;
  }

  .botanical-fan {
    right: -210px;
    opacity: 0.45;
  }
}