/* ============================================================
   Design tokens — "night dive" system
   Two page themes (light default / dark), but the dive-wave
   visualization is always rendered in its own fixed night
   palette (it depicts sleep at night, regardless of UI theme) —
   see the local override block on .wave-stage below.
   ============================================================ */
:root{
  /* ---- LIGHT THEME (default) ---- */
  --bg:#eef2fb;
  --glow-1:#c9d8ff66;
  --glow-2:#ffe8c655;
  --surface:#ffffff;
  --surface-alt:#f4f7fd;
  --sunken:#e7ecf9;
  --border:#d9e1f5;
  --hairline:#10183314;

  --text-hi:#101833;
  --text-mid:#4c587f;
  --text-low:#8592b8;

  --moon:#c8850f;
  --moon-ink:#241900;
  --moon-soft:#fbead0;
  --tide:#0f9488;
  --tide-soft:#e1f5f2;
  --coral:#c23652;
  --coral-soft:#fbe3e8;

  /* fixed "always night" palette used only inside .wave-stage */
  --night-text-hi:#eef3ff;
  --night-text-mid:#aab6dd;
  --night-text-low:#6c78a3;
  --night-moon:#f0b429;
  --night-tide:#33d6c0;

  --serif: "Fraunces", "Georgia", serif;
  --sans: "Manrope", "Inter", -apple-system, sans-serif;
  --mono: "Space Mono", "SF Mono", monospace;

  --radius: 20px;
  --radius-sm: 12px;
  --ease: cubic-bezier(.22,.9,.28,1);
}

[data-theme="dark"]{
  --bg:#0b1229;
  --glow-1:#1c2a5e55;
  --glow-2:#0d2b3c66;
  --surface:#121c40;
  --surface-alt:#16214a;
  --sunken:#0b1229;
  --border:#26315e;
  --hairline:#ffffff0d;

  --text-hi:#eef3ff;
  --text-mid:#aab6dd;
  --text-low:#6c78a3;

  --moon:#f0b429;
  --moon-ink:#241900;
  --moon-soft:#f0b42933;
  --tide:#33d6c0;
  --tide-soft:#33d6c022;
  --coral:#e8687a;
  --coral-soft:#e8687a22;
}

*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  min-height:100vh;
  background:
    radial-gradient(ellipse 900px 500px at 15% -10%, var(--glow-1), transparent 60%),
    radial-gradient(ellipse 700px 600px at 110% 10%, var(--glow-2), transparent 55%),
    var(--bg);
  color:var(--text-hi);
  font-family:var(--sans);
  line-height:1.5;
  -webkit-font-smoothing:antialiased;
  transition:background-color .3s var(--ease), color .3s var(--ease);
}
img,svg{display:block;max-width:100%;}
button{font-family:inherit;}
a{color:inherit;}

.wrap{max-width:920px;margin:0 auto;padding:0 24px;}

/* ---------------- Skip / focus ---------------- */
:focus-visible{outline:2px solid var(--tide);outline-offset:3px;border-radius:6px;}

/* ---------------- Header ---------------- */
.site-header{
  position:sticky;top:0;z-index:20;
  backdrop-filter:blur(14px);
  background:linear-gradient(to bottom, color-mix(in srgb, var(--bg) 92%, transparent), transparent);
  border-bottom:1px solid var(--hairline);
}
.site-header .inner{
  display:flex;align-items:center;justify-content:space-between;
  padding:16px 24px;max-width:920px;margin:0 auto;
  gap:12px;
}
.brand{display:flex;align-items:center;gap:10px;font-family:var(--serif);font-size:1.05rem;letter-spacing:.02em;color:var(--text-hi);}
.brand .dot{width:9px;height:9px;border-radius:50%;background:var(--moon);box-shadow:0 0 12px 3px var(--moon-soft);}

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

.theme-toggle{
  display:flex;align-items:center;justify-content:center;
  width:38px;height:38px;border-radius:50%;
  background:var(--surface);border:1px solid var(--border);
  color:var(--text-hi);cursor:pointer;flex-shrink:0;
  transition:background .2s var(--ease), transform .15s var(--ease);
}
.theme-toggle:hover{transform:translateY(-1px);}
.theme-toggle svg{width:18px;height:18px;}
.theme-toggle .icon-moon{display:none;}
[data-theme="dark"] .theme-toggle .icon-sun{display:none;}
[data-theme="dark"] .theme-toggle .icon-moon{display:block;}

.lang-switch{position:relative;}
.lang-switch select{
  appearance:none;
  background:var(--surface);
  color:var(--text-hi);
  border:1px solid var(--border);
  border-radius:999px;
  padding:8px 34px 8px 16px;
  font-size:.85rem;
  font-family:var(--sans);
  cursor:pointer;
}
.lang-switch::after{
  content:"▾";position:absolute;right:14px;top:50%;transform:translateY(-50%);
  color:var(--text-mid);pointer-events:none;font-size:.7rem;
}

/* ---------------- Hero ---------------- */
.hero{padding:64px 0 24px;position:relative;}
.eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  font-family:var(--mono);font-size:.72rem;letter-spacing:.12em;text-transform:uppercase;
  color:var(--tide);background:var(--tide-soft);
  border:1px solid var(--tide);
  border-color:color-mix(in srgb, var(--tide) 40%, transparent);
  padding:6px 14px;border-radius:999px;margin-bottom:22px;
}
.hero h1{
  font-family:var(--serif);
  font-weight:600;
  font-size:clamp(2.1rem, 5vw, 3.4rem);
  line-height:1.08;
  margin:0 0 18px;
  max-width:14ch;
  color:var(--text-hi);
}
.hero p{
  color:var(--text-mid);
  font-size:1.05rem;
  max-width:52ch;
  margin:0;
}

/* ---------------- Signature wave (the dive chart) ----------------
   Always rendered in its own fixed night palette regardless of the
   page theme — it's a window depicting nighttime sleep. */
.wave-stage{
  --text-hi:var(--night-text-hi);
  --text-mid:var(--night-text-mid);
  --text-low:var(--night-text-low);
  --moon:var(--night-moon);
  --tide:var(--night-tide);

  margin:44px 0 8px;
  border-radius:var(--radius);
  background:linear-gradient(180deg, #0e1836 0%, #0a1730 55%, #071022 100%);
  border:1px solid #26315e;
  overflow:hidden;
  position:relative;
}
.wave-stage svg{width:100%;height:auto;display:block;}
.wave-caption{
  display:flex;justify-content:space-between;align-items:center;
  padding:12px 20px 16px;font-family:var(--mono);font-size:.72rem;color:var(--text-low);
}
.wave-caption b{color:var(--moon);font-weight:700;}

/* ---------------- Calculator card ---------------- */
.calc{
  margin-top:40px;
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:28px;
}
.mode-toggle{
  display:flex;gap:8px;
  background:var(--sunken);
  border:1px solid var(--border);
  border-radius:999px;padding:5px;
  margin-bottom:22px;
}
.mode-toggle button{
  flex:1;border:none;background:transparent;color:var(--text-mid);
  padding:11px 14px;border-radius:999px;font-size:.88rem;font-weight:600;
  cursor:pointer;transition:background .25s var(--ease), color .25s var(--ease);
}
.mode-toggle button.active{background:var(--tide);color:#04211d;}

.input-row{
  display:flex;gap:12px;flex-wrap:wrap;align-items:flex-end;
}
.field{display:flex;flex-direction:column;gap:8px;flex:1;min-width:160px;}
.field label{font-size:.78rem;color:var(--text-mid);}
.field-head{display:flex;align-items:center;justify-content:space-between;gap:10px;}

.format-toggle{display:flex;gap:3px;background:var(--sunken);border:1px solid var(--border);border-radius:999px;padding:3px;flex-shrink:0;}
.format-toggle button{
  border:none;background:transparent;color:var(--text-mid);
  font-family:var(--mono);font-size:.68rem;font-weight:700;letter-spacing:.02em;
  padding:5px 10px;border-radius:999px;cursor:pointer;
  transition:background .2s var(--ease), color .2s var(--ease);
}
.format-toggle button.active{background:var(--tide);color:#04211d;}
.field input[type="time"]{
  background:var(--sunken);
  border:1px solid var(--border);
  color:var(--text-hi);
  font-family:var(--mono);
  font-size:1.4rem;
  padding:12px 14px;
  border-radius:var(--radius-sm);
  width:100%;
}
[data-theme="dark"] .field input[type="time"]{color-scheme:dark;}

.btn{
  border:none;border-radius:var(--radius-sm);
  padding:13px 18px;font-size:.88rem;font-weight:700;cursor:pointer;
  transition:transform .15s var(--ease), filter .15s var(--ease);
  white-space:nowrap;
}
.btn:hover{filter:brightness(1.06);}
.btn:active{transform:scale(.97);}
.btn-ghost{background:var(--sunken);color:var(--text-mid);border:1px solid var(--border);}
.btn-primary{background:var(--moon);color:var(--moon-ink);}

.helper-text{margin:14px 2px 0;color:var(--text-low);font-size:.82rem;}

/* ---------------- Preset chips ---------------- */
.presets{margin-top:18px;}
.presets .presets-label{
  font-size:.75rem;color:var(--text-low);text-transform:uppercase;
  letter-spacing:.08em;margin:0 0 10px;font-family:var(--mono);
}
.chip-row{
  display:flex;flex-wrap:wrap;gap:8px;
}
.chip{
  border:1px solid var(--border);
  background:var(--sunken);
  color:var(--text-mid);
  font-family:var(--mono);
  font-size:.82rem;
  padding:8px 13px;
  border-radius:999px;
  cursor:pointer;
  transition:border-color .15s var(--ease), color .15s var(--ease), background .15s var(--ease), transform .1s var(--ease);
}
.chip:hover{border-color:var(--tide);color:var(--text-hi);}
.chip:active{transform:scale(.96);}
.chip.selected{
  background:var(--tide);
  border-color:var(--tide);
  color:#04211d;
  font-weight:700;
}

/* ---------------- Results ---------------- */
.results{
  margin-top:26px;
  display:grid;
  grid-template-columns:repeat(auto-fit, minmax(150px,1fr));
  gap:12px;
}
.results:empty{display:none;}
.result-card{
  position:relative;
  background:var(--sunken);
  border:1px solid var(--border);
  border-radius:var(--radius-sm);
  padding:18px 16px;
  text-align:center;
  transition:transform .2s var(--ease), border-color .2s var(--ease);
}
.result-card:hover{transform:translateY(-3px);border-color:var(--tide);}
.result-card.ideal{
  border-color:var(--moon);
  background:linear-gradient(180deg, var(--moon-soft), var(--sunken) 75%);
}
.result-card .badge{
  position:absolute;top:-11px;left:50%;transform:translateX(-50%);
  background:var(--moon);color:var(--moon-ink);font-size:.65rem;font-weight:800;
  padding:3px 10px;border-radius:999px;white-space:nowrap;
  letter-spacing:.02em;
}
.result-card .time{
  font-family:var(--mono);font-size:1.7rem;font-weight:700;color:var(--text-hi);
  margin:6px 0 4px;
}
.result-card .cyc{font-size:.78rem;color:var(--text-mid);}
.result-card .dur{font-size:.72rem;color:var(--text-low);margin-top:2px;}
.result-card .quality{
  margin-top:10px;display:inline-block;font-size:.68rem;font-weight:700;
  padding:3px 10px;border-radius:999px;letter-spacing:.02em;
}
.q-short{background:var(--coral-soft);color:var(--coral);}
.q-good{background:var(--surface-alt);color:var(--text-mid);}
.q-ideal{background:var(--tide-soft);color:var(--tide);}
.q-long{background:var(--surface-alt);color:var(--text-mid);}

/* ---------------- Copy / share result ---------------- */
.results-actions{display:flex;justify-content:center;margin-top:18px;}
.results-actions .btn{min-width:180px;}

/* ---------------- Theory section ---------------- */
.theory{margin:80px 0 40px;}
.theory h2{
  font-family:var(--serif);font-size:1.9rem;margin:0 0 10px;color:var(--text-hi);
}
.theory > p{color:var(--text-mid);max-width:60ch;margin:0 0 30px;}
.stages{
  display:grid;grid-template-columns:repeat(auto-fit,minmax(190px,1fr));
  gap:14px;margin-bottom:34px;
}
.stage-card{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-sm);
  padding:20px;
}
.stage-card .num{
  font-family:var(--mono);color:var(--tide);font-size:.75rem;letter-spacing:.1em;
}
.stage-card h3{margin:8px 0 6px;font-size:1.02rem;font-family:var(--serif);font-weight:600;color:var(--text-hi);}
.stage-card p{margin:0;color:var(--text-mid);font-size:.87rem;}

.why-box{
  background:var(--surface-alt);border:1px solid var(--border);border-radius:var(--radius);
  padding:26px 28px;
}
.why-box h3{margin:0 0 10px;font-family:var(--serif);font-size:1.2rem;color:var(--text-hi);}
.why-box p{margin:0;color:var(--text-mid);}

/* ---------------- Footer ---------------- */
.site-footer{
  border-top:1px solid var(--hairline);padding:28px 0 60px;margin-top:40px;
  color:var(--text-low);font-size:.8rem;text-align:center;
}

/* ---------------- Motion ---------------- */
@media (prefers-reduced-motion: no-preference){
  .dive-path{stroke-dasharray:1400;stroke-dashoffset:1400;animation:draw 1.8s var(--ease) forwards;}
  @keyframes draw{to{stroke-dashoffset:0;}}
  .bubble{animation:bob 3.4s ease-in-out infinite;}
  @keyframes bob{0%,100%{transform:translateY(0);}50%{transform:translateY(-4px);}}
  .result-card{animation:rise .5s var(--ease) both;}
  @keyframes rise{from{opacity:0;transform:translateY(10px);}to{opacity:1;transform:translateY(0);}}
}

@media (max-width:600px){
  .hero{padding:40px 0 12px;}
  .calc{padding:20px;}
  .input-row{flex-direction:column;align-items:stretch;}
  .btn{width:100%;}
}