*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { background: var(--bg); color: var(--text); font-family: 'Inter', system-ui, sans-serif; }
body { min-height: 100vh; padding: 0 18px; max-width: 1560px; margin-inline: auto; }
@media (min-width: 768px)  { body { padding: 0 36px; } }
@media (min-width: 1080px) { body { padding: 0 56px; } }

/* ─────────────────────────────────────────────────────────
   DESIGN TOKENS — light default, dark override
───────────────────────────────────────────────────────── */
:root {
  /* Light mode */
  --bg:           #f2ebe0;   /* warm chart-paper cream */
  --bg-card:      #ffffff;
  --bg-card-hi:   #faf6f0;
  --bg-row:       #faf6f1;   /* alternating panel rows */
  --bg-alert-r:   rgba(192, 58, 46, 0.06);
  --bg-alert-a:   rgba(196, 136, 42, 0.06);

  --text:         #0b1e35;   /* deep nautical navy */
  --text-muted:   #456080;
  --text-dim:     #90aabb;

  --green:        #178a74;
  --amber:        #b8780e;
  --red:          #b83228;
  --brass:        #9a7d48;   /* nautical brass accent */
  --accent:       var(--green);
  --tide-water:   #1a4a7a;
  --river-water:  #1e3d3a;

  --border:       rgba(11, 30, 53, 0.10);
  --border-soft:  rgba(11, 30, 53, 0.06);
  --tide-water-soft: rgba(26,74,122,0.12);
  --brass-soft:      rgba(154,125,72,0.30);
  --brass-rule:      rgba(154,125,72,0.55);
  --svg-lock-bg:      #1e3a5c;
  --svg-lock-chamber: #2a5a80;
  --svg-lock-water:   #4a7aaa;
  --svg-lock-arrow:   #d0e8ff;
  --shadow:       0 1px 5px rgba(11, 30, 53, 0.08);
  --shadow-card:  0 2px 12px rgba(11, 30, 53, 0.07);

  /* SVG instrument panel palette — light mode: nautical-chart feel */
  --svg-bg:     #dce8f4;
  --svg-struct: #2a4a6a;
  --svg-water:  #4a7aaa;
  --svg-hull:   #2a5a80;
  --svg-cabin:  #3a6a90;
  --svg-mast:   #1e6a9a;
  --svg-win:    #b0c8e0;
  --svg-empty:  rgba(192,212,232,0.40);
  --svg-arrow:  #1a3a5a;
  --fuel-text:    #0b1e35;
  --fuel-muted:   #456080;
  --fuel-divider: rgba(11,30,53,0.10);
  --fuel-track:   rgba(11,30,53,0.07);
  --fc-track-gap: #F7C1C1;
  --fc-track-plan: #C0DD97;
  --fc-dot-gap: #178a74;
  --fc-dot-plan: #178a74;
  --fc-badge-gap-bg: #FCEBEB;
  --fc-badge-gap-text: #A32D2D;
  --fc-badge-plan-bg: #E1F5EE;
  --fc-badge-plan-text: #085041;
  --fc-label-gap: #A32D2D;
  --fc-label-plan: #178a74;
  --fc-tag-bg: #E1F5EE;
  --fc-tag-text: #085041;
  --fc-mid-border: #ffffff;
  --fc-port-name-color: #1a1a1a;
  --fc-port-fuel-color: #178a74;
  --fc-mi-label-color: #999999;
  --fc-dist-color: #bbbbbb;
  --fc-dist-gap-color: #A32D2D;
  --fc-dep-color: #aaaaaa;
  --fc-stop-name-color: #1a1a1a;
  --fc-row-border: rgba(0,0,0,0.07);
  --td-bg: #ffffff;
  --td-border: rgba(0,0,0,0.11);
  --td-row-hover: rgba(23,138,116,0.06);
  --td-selected-bg: rgba(23,138,116,0.09);
  --td-selected-border: #178a74;
  --td-text: #1a1a1a;
  --td-muted: #7a8a9a;
  --td-fuel-danger: #E24B4A;
  /* difficulty row */
  --dr-bg:              #f8f5f0;
  --dr-border:          rgba(11, 30, 53, 0.10);
  --dr-score:           #0b1e35;
  --dr-denom:           #90aabb;
  --dr-label:           #456080;
  --dr-pill-bg:         rgba(11, 30, 53, 0.07);
  --dr-pill-text:       #2a4060;
  --dr-pill-border:     rgba(11, 30, 53, 0.15);
  --dr-pill-warn-bg:    rgba(184, 120, 14, 0.10);
  --dr-pill-warn-text:  #7a4d06;
  --dr-pill-warn-border:rgba(184, 120, 14, 0.30);
  --dr-pill-alert-bg:   rgba(184, 50, 40, 0.08);
  --dr-pill-alert-text: #8a2020;
  --dr-pill-alert-border:rgba(184, 50, 40, 0.25);
}

[data-theme="dark"] {
  --bg:           #081929;
  --bg-card:      #0d2440;
  --bg-card-hi:   #112d4e;
  --bg-row:       #0a1e35;
  --bg-alert-r:   rgba(212, 82, 72, 0.09);
  --bg-alert-a:   rgba(212, 168, 74, 0.08);

  --text:         #ede8dc;
  --text-muted:   #7c9eb8;
  --text-dim:     #3d6080;

  --green:        #22c49a;
  --amber:        #d4a84a;
  --red:          #d45248;
  --brass:        #c4a870;
  --accent:       var(--green);

  --border:       rgba(30, 80, 135, 0.55);
  --border-soft:  rgba(30, 80, 135, 0.28);
  --tide-water:      #5a8aba;
  --tide-water-soft: rgba(90,138,186,0.16);
  --brass-soft:      rgba(196,168,112,0.30);
  --brass-rule:      rgba(196,168,112,0.55);
  --svg-lock-bg:      #0d2035;
  --svg-lock-chamber: #1a3a5c;
  --svg-lock-water:   #2a5a80;
  --svg-lock-arrow:   #d0e8ff;
  --shadow:       none;
  --shadow-card:  none;

  /* SVG instrument panel palette — dark mode: backlit wheelhouse */
  --svg-bg:     #1e3a5c;
  --svg-struct: #0d2035;
  --svg-water:  #1a4a6a;
  --svg-hull:   #4a7a9a;
  --svg-cabin:  #5a8aaa;
  --svg-mast:   #7ac0e0;
  --svg-win:    #0a1825;
  --svg-empty:  rgba(10,21,32,0.40);
  --svg-arrow:  rgba(255,255,255,0.85);
  --fuel-text:    #c8dced;
  --fuel-muted:   #7c9eb8;
  --fuel-divider: rgba(255,255,255,0.08);
  --fuel-track:   rgba(255,255,255,0.07);
  --fc-track-gap: #4a1010;
  --fc-track-plan: #27500A;
  --fc-dot-gap: #1db891;
  --fc-dot-plan: #1db891;
  --fc-badge-gap-bg: #2a0a0a;
  --fc-badge-gap-text: #f09595;
  --fc-badge-plan-bg: #04342C;
  --fc-badge-plan-text: #5DCAA5;
  --fc-label-gap: #f09595;
  --fc-label-plan: #1db891;
  --fc-tag-bg: #04342C;
  --fc-tag-text: #5DCAA5;
  --fc-mid-border: #132236;
  --fc-port-name-color: #c8dced;
  --fc-port-fuel-color: #1db891;
  --fc-mi-label-color: #4a7a9a;
  --fc-dist-color: #2a5a7a;
  --fc-dist-gap-color: #f09595;
  --fc-dep-color: #3a6a8a;
  --fc-stop-name-color: #c8dced;
  --fc-row-border: rgba(255,255,255,0.06);
  --td-bg: #0d2440;
  --td-border: rgba(255,255,255,0.10);
  --td-row-hover: rgba(23,138,116,0.10);
  --td-selected-bg: rgba(23,138,116,0.13);
  --td-selected-border: #22c49a;
  --td-text: #c8dced;
  --td-muted: #4a7a9a;
  --td-fuel-danger: #E24B4A;
  /* difficulty row */
  --dr-bg:              #0a1c30;
  --dr-border:          #1e3555;
  --dr-score:           #c8dced;
  --dr-denom:           #3d6080;
  --dr-label:           #4a7a9a;
  --dr-pill-bg:         rgba(255, 255, 255, 0.06);
  --dr-pill-text:       #8ab0cc;
  --dr-pill-border:     rgba(255, 255, 255, 0.12);
  --dr-pill-warn-bg:    rgba(212, 168, 74, 0.12);
  --dr-pill-warn-text:  #d4a84a;
  --dr-pill-warn-border:rgba(212, 168, 74, 0.30);
  --dr-pill-alert-bg:   rgba(212, 82, 72, 0.12);
  --dr-pill-alert-text: #d45248;
  --dr-pill-alert-border:rgba(212, 82, 72, 0.30);
}

/* ─────────────────────────────────────────────────────────
   HEADER
───────────────────────────────────────────────────────── */
header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 26px 0 22px;
  border-bottom: 1px solid var(--border-soft);
  gap: 12px;
  flex-wrap: wrap;
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--bg);
}

.logo {
  font-family: 'Playfair Display', serif;
  font-size: 30px;
  font-weight: 600;
  font-variant-caps: small-caps;
  letter-spacing: 0.06em;
  color: var(--text);
  line-height: 1;
  white-space: nowrap;
  text-decoration: none;
}
.logo .icw { color: var(--brass); }

.header-left {
  display: flex;
  align-items: center;
  gap: 10px;
}

.tagline {
  font-family: 'Playfair Display', Georgia, serif;
  font-style: italic;
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.3;
  letter-spacing: .01em;
  text-align: center;
  flex: 1;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

#clock {
  font-family: 'JetBrains Mono', monospace;
  font-size: 14px;
  color: var(--green);
  letter-spacing: .04em;
}

.theme-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 14px;
  cursor: pointer;
  padding: 5px 10px;
  border-radius: 4px;
  line-height: 1;
  transition: border-color .15s, color .15s;
}
.theme-btn:hover { border-color: var(--green); color: var(--text); }

/* ─────────────────────────────────────────────────────────
   SITE NAV
───────────────────────────────────────────────────────── */
.site-nav { display: flex; align-items: center; justify-content: center; padding: 0 20px; border-bottom: 1px solid var(--border-soft); position: sticky; top: 79px; z-index: 199; background: var(--bg); }
.site-nav-links { display: flex; align-items: center; gap: 0; justify-content: center; }
.nav-link { font-size: 13px; color: var(--text); padding: 10px 16px; border-bottom: 2px solid transparent; text-decoration: none; white-space: nowrap; transition: color 0.15s; }
.nav-link:hover { color: var(--text); }
.nav-link.active { color: var(--text); border-bottom-color: var(--text); font-weight: 500; }

@media (max-width: 640px) {
  header { display: grid; grid-template-columns: 1fr auto; grid-template-rows: auto auto; align-items: center; gap: 0; padding: 12px 16px; flex-wrap: unset; }
  .header-left { grid-column: 1; grid-row: 1; gap: 0; }
  .header-right { grid-column: 2; grid-row: 1; gap: 8px; }
  .tagline { grid-column: 1 / -1; grid-row: 2; font-size: 12px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; text-align: left; padding-top: 3px; flex: unset; }
  .site-nav-links { display: flex; overflow-x: auto; -webkit-overflow-scrolling: touch; }
  .nav-link { font-size: 12px; padding: 8px 10px; white-space: nowrap; }
  .site-nav { justify-content: flex-start; min-height: 40px; top: 74px; }
}