/* ============================================================================
   base.css — reset, typography, and the application shell.

   Layout model: four fixed regions (water field, topbar, depth rail,
   instrument strip) with one scrolling region between them. The rail and the
   strip are `position: fixed` rather than grid tracks so that the page can
   scroll at 60 fps without the browser reflowing them, and so that a long
   atlas listing never pushes the readout off screen.
   ========================================================================= */

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

* { margin: 0; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scrollbar-color: var(--line-2) transparent;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  min-height: 100dvh;
  background: var(--bg-0);
  color: var(--text-0);
  font-family: var(--font-sans);
  font-size: var(--t-0);
  line-height: var(--lh-body);
  letter-spacing: var(--tr-normal);
  font-synthesis-weight: none;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  transition: background var(--d-slow) var(--ease-out), color var(--d-slow) var(--ease-out);
}

img, svg, canvas, video { display: block; max-width: 100%; }
svg { flex: none; }

button, input, select, textarea {
  font: inherit;
  color: inherit;
  letter-spacing: inherit;
}

button { background: none; border: none; cursor: pointer; }

a { color: inherit; text-decoration: none; }

ul, ol { list-style: none; padding: 0; }

hr {
  border: none;
  border-top: 1px solid var(--line-1);
  margin: var(--s-6) 0;
}

::selection {
  background: var(--accent);
  color: var(--accent-ink);
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--r-1);
}

.skip-link {
  position: fixed;
  top: var(--s-3);
  left: var(--s-3);
  z-index: 999;
  padding: var(--s-3) var(--s-4);
  background: var(--accent);
  color: var(--accent-ink);
  border-radius: var(--r-2);
  font-weight: 600;
  transform: translateY(-200%);
  transition: transform var(--d-fast) var(--ease-out);
}
.skip-link:focus { transform: translateY(0); }

/* ── Scrollbar ────────────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 11px; height: 11px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: var(--line-2);
  border-radius: var(--r-full);
  border: 3px solid transparent;
  background-clip: content-box;
}
::-webkit-scrollbar-thumb:hover { background-clip: content-box; background-color: var(--line-strong); }

/* ============================================================================
   Water field — the fixed background
   ========================================================================= */

.water {
  position: fixed;
  inset: 0;
  z-index: var(--z-water);
  pointer-events: none;
  overflow: hidden;
  background:
    linear-gradient(
      180deg,
      var(--water-top) 0%,
      var(--water-mid) 22%,
      var(--water-deep) 62%,
      var(--bg-void) 100%
    );
  transition: background var(--d-slow) linear;
}

/* The gradient is driven by scroll depth via --depth-progress (0..1), set on
   <html> by the scroll observer. */
.water__glow {
  position: absolute;
  inset: -20% -10% auto -10%;
  height: 75vh;
  background: radial-gradient(
    ellipse 70% 55% at 50% 0%,
    color-mix(in oklab, var(--water-top) 85%, white 15%) 0%,
    transparent 68%
  );
  opacity: calc(0.9 - var(--depth-progress, 0) * 0.92);
  transition: opacity var(--d-slow) linear;
  filter: blur(8px);
}

/* God rays through the surface. Pure CSS, and they fade out entirely by the
   time the reader has descended past the photic zone. */
.water__rays {
  position: absolute;
  inset: -30% -20% auto -20%;
  height: 130vh;
  opacity: calc(var(--ray-opacity) * (1 - var(--depth-progress, 0) * 1.6));
  background: repeating-linear-gradient(
    99deg,
    transparent 0 44px,
    color-mix(in oklab, var(--water-top) 60%, white 40%) 44px 52px,
    transparent 52px 128px
  );
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.85) 0%, transparent 78%);
  -webkit-mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.85) 0%, transparent 78%);
  filter: blur(14px);
  animation: rays-drift 26s var(--ease-in-out) infinite alternate;
  transition: opacity var(--d-slow) linear;
}

@keyframes rays-drift {
  from { transform: translate3d(-2%, 0, 0) skewX(0deg); }
  to   { transform: translate3d(2%, 0, 0) skewX(1.4deg); }
}

#marine-snow {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: var(--snow-opacity);
}

/* ============================================================================
   Topbar
   ========================================================================= */

.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--topbar-h);
  z-index: var(--z-topbar);
  background: var(--surface-glass);
  backdrop-filter: blur(18px) saturate(150%);
  -webkit-backdrop-filter: blur(18px) saturate(150%);
  border-bottom: 1px solid var(--line-1);
}

.topbar__inner {
  height: 100%;
  max-width: var(--page-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
  display: flex;
  align-items: center;
  gap: var(--s-5);
}

.topbar__progress {
  position: absolute;
  left: 0;
  right: 0;
  bottom: -1px;
  height: 2px;
  overflow: hidden;
}
.topbar__progress span {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--accent), var(--lure));
  opacity: 0;
  transition: width var(--d-base) var(--ease-out), opacity var(--d-fast) linear;
}
.topbar__progress span.is-active { opacity: 1; }

/* ── Brand ────────────────────────────────────────────────────────────── */
.brand {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  flex: none;
}
.brand__mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  color: var(--accent);
  border: 1px solid var(--accent-line);
  border-radius: var(--r-2);
  background: var(--accent-soft);
}
.brand__mark svg { width: 20px; height: 20px; }
.brand__text { display: flex; flex-direction: column; line-height: 1.1; }
.brand__name {
  font-family: var(--font-mono);
  font-size: var(--t-1);
  font-weight: 600;
  letter-spacing: var(--tr-wider);
}
.brand__sub {
  font-size: var(--t--2);
  color: var(--text-2);
  letter-spacing: var(--tr-wide);
  text-transform: uppercase;
}

/* ── Nav ──────────────────────────────────────────────────────────────── */
.nav {
  display: flex;
  align-items: center;
  gap: var(--s-1);
  margin-inline-start: auto;
  overflow-x: auto;
  scrollbar-width: none;
  /* The links do not fit on a phone, so this strip scrolls. Snap so a swipe
     settles on a whole link, and fade the trailing edge so it reads as
     "more this way" rather than as a truncation bug. */
  scroll-snap-type: x proximity;
  scroll-padding-inline: var(--s-3);
  -webkit-overflow-scrolling: touch;
}
.nav::-webkit-scrollbar { display: none; }

.nav a {
  position: relative;
  padding: var(--s-2) var(--s-3);
  border-radius: var(--r-2);
  font-size: var(--t--1);
  font-weight: 500;
  color: var(--text-1);
  white-space: nowrap;
  scroll-snap-align: start;
  transition: color var(--d-fast) linear, background var(--d-fast) linear;
}
.nav a:hover { color: var(--text-0); background: var(--surface-2); }
.nav a[aria-current="page"] { color: var(--accent); }
.nav a[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: var(--s-3);
  right: var(--s-3);
  bottom: 2px;
  height: 1.5px;
  border-radius: 2px;
  background: var(--accent);
}

.topbar__actions { display: flex; align-items: center; gap: var(--s-2); flex: none; }

/* ============================================================================
   Depth rail
   ========================================================================= */

.rail {
  position: fixed;
  top: var(--topbar-h);
  bottom: var(--strip-h);
  left: 0;
  width: var(--rail-w);
  z-index: var(--z-rail);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--s-3);
  padding: var(--s-5) 0 var(--s-4);
  border-right: 1px solid var(--line-1);
  background: linear-gradient(90deg, var(--surface-glass), transparent);
}

.rail__label {
  font-family: var(--font-mono);
  font-size: 9px;
  letter-spacing: var(--tr-wider);
  color: var(--text-3);
  writing-mode: vertical-rl;
  text-orientation: mixed;
}

.rail__scale {
  position: relative;
  flex: 1;
  width: 100%;
  min-height: 0;
}

.rail__track {
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 1px;
  transform: translateX(-50%);
  background: linear-gradient(
    180deg,
    var(--line-2),
    var(--line-1) 55%,
    transparent 100%
  );
}

/* Zone bands: each zone gets a proportional slice of the track, tinted with
   its own accent so the rail doubles as a legend.
   The accents darken steeply with depth (hadal is #0b2a3d), which would make
   the deep bands invisible on a near-black background. Each band is therefore
   lifted toward a legible mid-tone while keeping its hue, so all five read as
   distinct at a glance without losing the sense that the water gets darker. */
.rail__zones { position: absolute; inset: 0; }

.rail__zone {
  position: absolute;
  left: 50%;
  width: 6px;
  transform: translateX(-50%);
  border-radius: var(--r-full);
  background: color-mix(in oklab, var(--zone-accent) 58%, var(--text-2));
  opacity: 0.55;
  transition:
    opacity var(--d-base) var(--ease-out),
    width var(--d-base) var(--ease-out),
    box-shadow var(--d-base) var(--ease-out);
}
.rail__zone.is-active {
  opacity: 1;
  width: 10px;
  background: var(--zone-accent);
  box-shadow: 0 0 14px -1px color-mix(in oklab, var(--zone-accent) 70%, transparent);
}

.rail__marker {
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  display: flex;
  align-items: center;
  gap: var(--s-2);
  transform: translateY(-50%);
  transition: top var(--d-base) var(--ease-out);
  will-change: top;
}

.rail__marker-line {
  flex: none;
  margin-left: auto;
  margin-right: calc(50% - 7px);
  width: 14px;
  height: 2px;
  border-radius: 2px;
  background: var(--accent);
  box-shadow: var(--shadow-glow);
}

.rail__marker-value {
  position: absolute;
  left: calc(50% + 14px);
  font-family: var(--font-mono);
  font-size: 10px;
  font-variant-numeric: tabular-nums;
  color: var(--accent);
  white-space: nowrap;
  background: var(--surface-glass);
  padding: 1px 5px;
  border-radius: var(--r-1);
  backdrop-filter: blur(6px);
}

.rail__foot {
  font-family: var(--font-mono);
  font-size: 9px;
  letter-spacing: var(--tr-wide);
  text-transform: uppercase;
  color: var(--text-3);
  text-align: center;
  line-height: 1.3;
  max-width: 100%;
  padding-inline: 4px;
  overflow-wrap: anywhere;
}

/* ============================================================================
   Main scroll region
   ========================================================================= */

.main {
  position: relative;
  z-index: var(--z-content);
  margin-left: var(--rail-w);
  padding-top: var(--topbar-h);
  padding-bottom: var(--strip-h);
  min-height: 100dvh;
}
.main:focus { outline: none; }

.view { min-height: calc(100dvh - var(--topbar-h) - var(--strip-h)); }

/* ── Page container ───────────────────────────────────────────────────── */
.page {
  max-width: var(--page-max);
  margin-inline: auto;
  padding: var(--s-7) var(--gutter) var(--s-9);
}

.page--wide { max-width: 1560px; }

/* ── Boot state ───────────────────────────────────────────────────────── */
.boot {
  display: grid;
  place-items: center;
  gap: var(--s-5);
  min-height: 60vh;
  color: var(--text-2);
}
.boot__ring {
  width: 46px;
  height: 46px;
  border-radius: 50%;
  border: 2px solid var(--line-2);
  border-top-color: var(--accent);
  animation: spin 900ms linear infinite;
}
.boot__text {
  font-family: var(--font-mono);
  font-size: var(--t--1);
  letter-spacing: var(--tr-wide);
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ============================================================================
   Instrument strip
   ========================================================================= */

.strip {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  height: var(--strip-h);
  z-index: var(--z-strip);
  background: var(--surface-glass);
  backdrop-filter: blur(18px) saturate(150%);
  -webkit-backdrop-filter: blur(18px) saturate(150%);
  border-top: 1px solid var(--line-1);
  padding-bottom: var(--strip-safe);
}

.strip__inner {
  height: calc(100% - var(--strip-safe));
  max-width: var(--page-max);
  margin-inline: auto;
  padding-inline: var(--gutter);
  display: flex;
  align-items: center;
  gap: var(--s-5);
}

.strip__lead {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  flex: none;
  padding-right: var(--s-5);
  border-right: 1px solid var(--line-1);
  height: 60%;
}

.strip__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 0 var(--accent-line);
  animation: pulse 2.4s var(--ease-in-out) infinite;
}
@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 0 var(--accent-line); }
  50% { box-shadow: 0 0 0 7px transparent; }
}

.strip__depth {
  font-family: var(--font-mono);
  font-size: var(--t-2);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  letter-spacing: var(--tr-tight);
  color: var(--text-0);
  line-height: 1;
}
.strip__depth small {
  font-size: max(0.5em, 11px);
  color: var(--text-2);
  margin-left: 2px;
  font-weight: 400;
}
.strip__zone {
  font-size: var(--t--2);
  letter-spacing: var(--tr-wide);
  text-transform: uppercase;
  color: var(--text-2);
}

.strip__grid {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: minmax(84px, 1fr);
  gap: var(--s-1) var(--s-5);
  align-content: center;
  flex: 1;
  min-width: 0;
  overflow-x: auto;
  scrollbar-width: none;
}
.strip__grid::-webkit-scrollbar { display: none; }

.readout { min-width: 0; }
.readout dt {
  font-size: 9.5px;
  line-height: 1.3;
  letter-spacing: var(--tr-wide);
  text-transform: uppercase;
  color: var(--text-3);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.readout dd {
  font-family: var(--font-mono);
  font-size: var(--t--1);
  line-height: 1.25;
  font-variant-numeric: tabular-nums;
  letter-spacing: var(--tr-tight);
  color: var(--text-0);
  white-space: nowrap;
  transition: color var(--d-fast) linear;
}
/* The unit rides along with the figure but should never compete with it. */
.readout__u {
  font-size: 0.82em;
  color: var(--text-2);
  margin-left: 0.28em;
}
.readout dd.is-flash { color: var(--accent); }

.strip__tail { flex: none; }

/* ============================================================================
   Responsive
   ========================================================================= */

@media (max-width: 1180px) {
  :root { --rail-w: 76px; }
  .brand__sub { display: none; }
}

@media (max-width: 900px) {
  :root {
    --rail-w: 0px;
    --strip-h: calc(92px + var(--strip-safe));
  }
  .rail { display: none; }
  .main { margin-left: 0; }

  .strip__inner {
    flex-wrap: wrap;
    gap: var(--s-2) var(--s-4);
    padding-block: var(--s-2);
    align-content: center;
  }
  .strip__lead {
    border-right: none;
    padding-right: 0;
    height: auto;
    width: 100%;
    gap: var(--s-2);
  }
  .strip__depth { font-size: var(--t-1); }
  .strip__grid {
    grid-auto-columns: minmax(70px, 1fr);
    gap: var(--s-1) var(--s-4);
  }
  .strip__tail { display: none; }
}

@media (max-width: 640px) {
  :root { --topbar-h: 56px; }
  /* Claw back width for the nav: the topbar's 24px gaps cost more than the
     links they separate. */
  .topbar__inner { gap: var(--s-2); }
  .nav {
    gap: 0;
    mask-image: linear-gradient(to right, #000 calc(100% - 18px), transparent);
    -webkit-mask-image: linear-gradient(to right, #000 calc(100% - 18px), transparent);
  }
  .nav a { padding: var(--s-2); font-size: var(--t--2); }
  .brand__text { display: none; }
  .iconbtn__hint { display: none; }
  /* Two rows of three readouts need room the one-line desktop strip doesn't,
     and the figures are set tighter so nothing wraps at 360px. */
  :root { --strip-h: calc(124px + var(--strip-safe)); }
  .strip__inner { padding-block: var(--s-2); gap: var(--s-1) var(--s-3); }
  .strip__lead { gap: var(--s-2); }
  .strip__depth { font-size: var(--t-1); }
  .strip__zone {
    font-size: var(--t--2);
    letter-spacing: var(--tr-wide);
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }
  .strip__grid {
    grid-auto-flow: row;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: var(--s-2) var(--s-3);
    overflow: visible;
  }
  /* Stacked on a phone the strip reads as a small table, so each cell is
     centred on its column and the depth line is centred over them — a
     left-flush run of ragged figures looks like an accident at this size. */
  .strip__lead { justify-content: center; }
  .readout { text-align: center; }
  .readout dt { font-size: 10.5px; }
  .readout dd { font-size: var(--t--1); }
}

/* ── Print ────────────────────────────────────────────────────────────── */
@media print {
  .water, .rail, .strip, .topbar, .palette, .drawer, .toasts { display: none !important; }
  .main { margin: 0; padding: 0; }
  body { background: #fff; color: #000; }
}