/* ============================================================
   Eleven Thousand Metres
   ============================================================ */

:root{
  --water: #56c5d6;
  --ink: #eaf6fb;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  --measure: 34rem;
  --pad: clamp(1.25rem, 5vw, 4rem);
}

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

html{
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body{
  margin: 0;
  background: #04121a;
  color: var(--ink);
  font-family: var(--serif);
  font-size: clamp(1rem, 0.94rem + 0.28vw, 1.11rem);
  line-height: 1.62;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* ---------- the water ---------- */

.water{
  position: fixed;
  inset: 0;
  z-index: -3;
  background: var(--water);
  transition: background-color 120ms linear;
}

/* a soft darkening toward the edges, deepens as you descend */
.water::after{
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(120% 80% at 50% 0%, transparent 20%, rgba(0,0,0,.55) 100%);
  opacity: var(--vignette, .35);
}

/* god rays, fading out by ~150 m */
.sunbeams{
  position: fixed;
  inset: -20% 0 auto 0;
  height: 90vh;
  z-index: -2;
  pointer-events: none;
  opacity: var(--beams, 1);
  background:
    linear-gradient(172deg, rgba(255,255,255,.30) 0 2%, transparent 2.6%) 8% 0/ 40% 100% no-repeat,
    linear-gradient(188deg, rgba(255,255,255,.22) 0 1.4%, transparent 2%) 34% 0/ 40% 100% no-repeat,
    linear-gradient(176deg, rgba(255,255,255,.26) 0 2.4%, transparent 3%) 62% 0/ 40% 100% no-repeat,
    linear-gradient(191deg, rgba(255,255,255,.18) 0 1.2%, transparent 1.8%) 86% 0/ 40% 100% no-repeat;
  filter: blur(6px);
  mask-image: linear-gradient(to bottom, #000 0%, transparent 85%);
  -webkit-mask-image: linear-gradient(to bottom, #000 0%, transparent 85%);
  animation: sway 14s ease-in-out infinite alternate;
}
@keyframes sway{ from{ transform: skewX(-1.6deg); } to{ transform: skewX(1.6deg); } }

/* marine snow */
.snow{
  position: fixed;
  inset: 0;
  z-index: -1;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

/* ---------- instruments ---------- */

.hud{
  position: fixed;
  top: max(1rem, env(safe-area-inset-top));
  left: var(--pad);
  z-index: 20;
  display: flex;
  flex-direction: column;
  gap: .35rem;
  font-family: var(--mono);
  font-size: .72rem;
  letter-spacing: .06em;
  text-transform: uppercase;
  padding: .7rem .9rem;
  border: 1px solid rgba(255,255,255,.18);
  border-radius: .55rem;
  background: rgba(0,20,32,.28);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  mix-blend-mode: normal;
}
.hud-row{ display: flex; justify-content: space-between; gap: 1.4rem; }
.hud-label{ opacity: .55; }
.hud-value{ font-variant-numeric: tabular-nums; font-style: normal; }
.hud-value i{ font-style: normal; opacity: .5; margin-left: .18em; font-size: .85em; }

.rail{
  position: fixed;
  right: calc(var(--pad) * .7);
  top: 12vh;
  bottom: 12vh;
  width: 2rem;
  z-index: 20;
  font-family: var(--mono);
  font-size: .6rem;
  letter-spacing: .05em;
}
.rail-line{
  position: absolute;
  left: 50%;
  top: 0; bottom: 0;
  width: 1px;
  background: linear-gradient(to bottom, rgba(255,255,255,.05), rgba(255,255,255,.3), rgba(255,255,255,.05));
}
.rail-marker{
  position: absolute;
  left: 50%;
  top: 0;
  width: 9px; height: 9px;
  margin-left: -4.5px; margin-top: -4.5px;
  border-radius: 50%;
  background: #fff;
  box-shadow: 0 0 12px rgba(255,255,255,.9);
  will-change: top;
}
.rail-tick{
  position: absolute;
  right: 100%;
  margin-right: .4rem;
  transform: translateY(-50%);
  opacity: .4;
  white-space: nowrap;
}

/* ---------- surface ---------- */

.hero{
  position: relative;
  min-height: 100svh;
  display: grid;
  align-content: center;
  padding: 22vh var(--pad) 18vh;
  overflow: hidden;
}

.hero-copy{ position: relative; z-index: 2; max-width: var(--measure); }

.kicker{
  font-family: var(--mono);
  font-size: .72rem;
  letter-spacing: .22em;
  text-transform: uppercase;
  opacity: .7;
  margin: 0 0 1.4rem;
}

h1{
  font-size: clamp(3.2rem, 13vw, 8.5rem);
  line-height: .88;
  letter-spacing: -.03em;
  font-weight: 400;
  margin: 0 0 1.6rem;
  text-shadow: 0 2px 40px rgba(0,30,50,.4);
}

.hero-lede{
  max-width: 30rem;
  font-size: 1.15em;
  margin: 0;
  text-wrap: pretty;
}

/* dolphins */
.pod{
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  opacity: .9;
}
/* solid fill + element-level opacity, so the overlapping body / fin / fluke
   shapes composite as one silhouette instead of double-darkening at the seams */
.dolphin{
  position: absolute;
  fill: #093549;
  opacity: .5;
  filter: drop-shadow(0 6px 24px rgba(0,20,40,.3));
  width: 34vmin;
  will-change: transform;
}
.dolphin{ --detail-eye: rgba(186,224,240,.5); --detail-line: rgba(186,224,240,.32); }
.d1{ top: 8%;  left: -40%; animation: swim 26s linear infinite, bob 4.5s ease-in-out infinite alternate; }
.d2{ top: 62%; left: -40%; width: 24vmin; opacity: .34; animation: swim 34s linear infinite 6s, bob 5.5s ease-in-out infinite alternate; }
.d3{ top: 38%; left: -40%; width: 17vmin; opacity: .22; animation: swim 44s linear infinite 14s, bob 6.5s ease-in-out infinite alternate; }

@keyframes swim{
  from{ transform: translateX(0) }
  to  { transform: translateX(240vw) }
}
@keyframes bob{
  from{ margin-top: -2.5vh; rotate: -4deg }
  to  { margin-top:  2.5vh; rotate:  4deg }
}

.scroll-cue{
  position: absolute;
  left: 50%;
  bottom: 3.5rem;
  transform: translateX(-50%);
  z-index: 3;
  display: grid;
  justify-items: center;
  gap: .5rem;
  font-family: var(--mono);
  font-size: .65rem;
  letter-spacing: .2em;
  text-transform: uppercase;
  opacity: .75;
  animation: nudge 2.6s ease-in-out infinite;
}
.scroll-cue svg{ width: 1rem; }
@keyframes nudge{ 0%,100%{ transform: translate(-50%,0) } 50%{ transform: translate(-50%,10px) } }

/* ---------- zones ---------- */

.zone{
  min-height: 170vh;
  display: grid;
  align-items: center;
  padding: 20vh var(--pad);
}

.zone-inner{
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, var(--measure));
  gap: clamp(2rem, 6vw, 6rem);
  align-items: center;
  max-width: 78rem;
  margin: 0 auto;
  width: 100%;
}

.zone:nth-of-type(even) .zone-inner{ direction: rtl; }
.zone:nth-of-type(even) .zone-copy{ direction: ltr; }

.zone-art{
  margin: 0;
  display: grid;
  place-items: center;
}
.zone-art .art{
  width: min(100%, 34rem);
  fill: var(--accent);
  opacity: .72;                /* on the element, so overlapping parts don't stack */
  filter: drop-shadow(0 0 40px color-mix(in oklab, var(--accent) 35%, transparent));
}

.zone-copy{
  opacity: 0;
  transform: translateY(2.2rem);
  transition: opacity .9s ease, transform .9s cubic-bezier(.2,.7,.3,1);
}
.zone.in .zone-copy{ opacity: 1; transform: none; }

.zone-range{
  font-family: var(--mono);
  font-size: .72rem;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 .8rem;
}

.zone h2{
  font-size: clamp(2rem, 5.4vw, 3.1rem);
  line-height: 1;
  letter-spacing: -.02em;
  font-weight: 400;
  margin: 0 0 .4rem;
}

.zone-latin{
  font-style: italic;
  opacity: .55;
  margin: 0 0 1.8rem;
  font-size: .95em;
}

.zone p{ text-wrap: pretty; max-width: 36rem; }
.zone b{ font-weight: 600; color: var(--accent); }

.facts{
  list-style: none;
  padding: 0;
  margin: 2.2rem 0 0;
  display: grid;
  gap: .1rem;
  border-top: 1px solid rgba(255,255,255,.14);
  max-width: 30rem;
}
.facts li{
  font-family: var(--sans);
  font-size: .82rem;
  letter-spacing: .01em;
  padding: .7rem .1rem;
  border-bottom: 1px solid rgba(255,255,255,.09);
  opacity: .8;
}
.facts b{ font-weight: 600; }

/* per-creature life */
.art-dolphin{ --detail-eye: #06202c; --detail-line: rgba(4,30,42,.5); }

.art-lantern .eye-big{ fill: rgba(255,255,255,.85); }
.art-lantern .pupil{ fill: #0b1030; }
.art-lantern .photophores circle{
  fill: #eef7ff;
  filter: drop-shadow(0 0 7px #bfe0ff);
  animation: blink 3.4s ease-in-out infinite;
}
.art-lantern .photophores circle:nth-child(2){ animation-delay: .3s }
.art-lantern .photophores circle:nth-child(3){ animation-delay: .6s }
.art-lantern .photophores circle:nth-child(4){ animation-delay: .9s }
.art-lantern .photophores circle:nth-child(5){ animation-delay: 1.2s }
.art-lantern .photophores circle:nth-child(6){ animation-delay: 1.5s }
.art-lantern .photophores circle:nth-child(7){ animation-delay: 1.8s }
@keyframes blink{ 0%,100%{ opacity:.4 } 50%{ opacity:1 } }

.art-angler .mouth{ fill: #0d0820; }
.art-angler .teeth path{ fill: #f4f0ff; }
.art-angler .rod{ stroke: var(--accent); }
.art-angler .esca{
  fill: #fffbe8;
  filter: drop-shadow(0 0 9px #ffe680) drop-shadow(0 0 28px rgba(255,206,74,.85));
  animation: lure 3.8s ease-in-out infinite;
}
/* the r property needs a unit in CSS — a bare number is invalid and drops the frame.
   opacity stays high: this is the only light source in the picture. */
@keyframes lure{ 0%,100%{ opacity:.85; r:9px } 50%{ opacity:1; r:11.5px } }
.art-angler .eye-big{ fill: #f6f2ff; }
.art-angler .pupil{ fill: #0d0820; }

.art-dumbo .ear{ opacity: .85; animation: flap 5s ease-in-out infinite alternate; transform-origin: 120px 40px; }
.art-dumbo .arm{ opacity: .7; }
.art-dumbo .eye{ fill: #05201a; }
@keyframes flap{ from{ transform: rotate(-5deg) } to{ transform: rotate(5deg) } }

.art-snailfish{ opacity: .85; }
.art-snailfish .finline{ fill: rgba(255,255,255,.25); }
.art-snailfish .eye{ fill: #2a0f08; }

/* ---------- the floor ---------- */

.floor{
  min-height: 130vh;
  display: grid;
  align-items: center;
  padding: 22vh var(--pad) 16vh;
  position: relative;
}
.floor::before{
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: 0;
  height: 34vh;
  background: linear-gradient(to top, #0a0806 20%, rgba(10,8,6,0));
  z-index: -1;
}
.floor-inner{
  max-width: 40rem;
  margin: 0 auto;
  text-align: center;
}
.floor-depth{
  font-family: var(--mono);
  font-size: .78rem;
  letter-spacing: .3em;
  text-transform: uppercase;
  opacity: .6;
  margin: 0 0 1rem;
}
.floor h2{
  font-size: clamp(2.6rem, 9vw, 5rem);
  line-height: .95;
  letter-spacing: -.03em;
  font-weight: 400;
  margin: 0 0 1rem;
}
.floor-sub{
  font-style: italic;
  opacity: .7;
  margin: 0 0 3rem;
}
.floor-body{ text-align: left; max-width: 34rem; margin: 0 auto; }
.floor-body p{ text-wrap: pretty; }

.bag{
  margin: 4rem auto;
  max-width: 15rem;
  text-align: center;
}
.bag .art{
  width: 100%;
  fill: rgba(226,236,240,.16);
  stroke: rgba(226,236,240,.5);
  stroke-width: 2.5;
  animation: waft 9s ease-in-out infinite alternate;
}
.bag .baghandle, .bag .bagcrease{ stroke: rgba(226,236,240,.45); }
@keyframes waft{
  from{ transform: rotate(-3deg) translateY(-6px) }
  to  { transform: rotate(3deg)  translateY(6px) }
}
.bag figcaption{
  font-family: var(--mono);
  font-size: .68rem;
  letter-spacing: .1em;
  text-transform: uppercase;
  opacity: .55;
  margin-top: 1.4rem;
}

.floor-punch{
  font-size: 1.25em;
  line-height: 1.45;
  margin-top: 2.5rem;
  padding-top: 2rem;
  border-top: 1px solid rgba(255,255,255,.15);
  text-wrap: balance;
}

/* ---------- ascent ---------- */

.outro{
  min-height: 70vh;
  display: grid;
  align-content: center;
  justify-items: center;
  gap: 2.5rem;
  padding: 12vh var(--pad) calc(8vh + env(safe-area-inset-bottom));
  text-align: center;
  background: #0a0806;
}
.outro-line{
  max-width: 30rem;
  margin: 0;
  font-size: 1.1em;
  opacity: .85;
  text-wrap: pretty;
}
.surface-btn{
  font-family: var(--mono);
  font-size: .75rem;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: inherit;
  background: transparent;
  border: 1px solid rgba(255,255,255,.35);
  border-radius: 100px;
  padding: 1rem 1.8rem;
  cursor: pointer;
  transition: background-color .25s ease, border-color .25s ease, transform .25s ease;
}
.surface-btn:hover, .surface-btn:focus-visible{
  background: rgba(255,255,255,.1);
  border-color: rgba(255,255,255,.7);
  transform: translateY(-2px);
}
.colophon{
  max-width: 30rem;
  margin: 0;
  font-family: var(--sans);
  font-size: .72rem;
  line-height: 1.7;
  opacity: .38;
}

:focus-visible{ outline: 2px solid #8ff0ff; outline-offset: 3px; }

/* ---------- mobile ---------- */

@media (max-width: 860px){
  .zone-inner{
    grid-template-columns: 1fr;
    gap: 2.5rem;
  }
  .zone:nth-of-type(even) .zone-inner{ direction: ltr; }
  .zone-art{ order: -1; }
  .zone-art .art{ width: min(78%, 22rem); }
  .zone{ min-height: 130vh; padding: 14vh var(--pad); }
  .rail{ display: none; }
  .hud{
    left: 50%;
    transform: translateX(-50%);
    flex-direction: row;
    gap: 1rem;
    padding: .5rem .8rem;
    font-size: .62rem;
  }
  .hud-row{ flex-direction: column; gap: .1rem; align-items: center; }
  .hero{ padding-top: 26vh; }
  .dolphin{ width: 52vmin; }
  .d2{ width: 38vmin } .d3{ width: 28vmin }
}

@media (max-width: 420px){
  .hud{ gap: .7rem; }
  .facts li{ font-size: .78rem; }
}

/* ---------- motion & contrast preferences ---------- */

@media (prefers-reduced-motion: reduce){
  html{ scroll-behavior: auto; }
  .dolphin, .sunbeams, .scroll-cue,
  .art-lantern .photophores circle, .art-angler .esca,
  .art-dumbo .ear, .bag .art{
    animation: none !important;
  }
  .d1{ left: 12% } .d2{ left: 58% } .d3{ left: 34% }
  .zone-copy{ opacity: 1; transform: none; transition: none; }
  .water{ transition: none; }
}