:root {
  --bg: #0d1017;
  --bg-soft: #141924;
  --surface: #171d2a;
  --surface-2: #1e2534;
  --border: #2a3244;
  --text: #e8ecf4;
  --text-dim: #9aa7bd;
  --accent: #5eead4;
  --accent-2: #818cf8;
  --accent-ink: #06231f;
  --shadow: 0 20px 50px -20px rgba(0, 0, 0, .8);
  --radius: 16px;
  --wrap: 940px;
}

html[data-theme="light"] {
  --bg: #f6f8fc;
  --bg-soft: #eef2f9;
  --surface: #ffffff;
  --surface-2: #f2f5fb;
  --border: #dde4f0;
  --text: #131926;
  --text-dim: #5a6883;
  --accent: #0d9488;
  --accent-2: #4f46e5;
  --accent-ink: #ffffff;
  --shadow: 0 18px 40px -24px rgba(20, 32, 60, .35);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .001ms !important; transition-duration: .001ms !important; }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 400 17px/1.65 ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
}

.wrap { width: min(100% - 2.5rem, var(--wrap)); margin-inline: auto; }

a { color: var(--accent); }
a:focus-visible, button:focus-visible, select:focus-visible, input:focus-visible, summary:focus-visible {
  outline: 2px solid var(--accent-2);
  outline-offset: 3px;
  border-radius: 6px;
}

.skip-link {
  position: absolute; left: -9999px; top: 0; z-index: 20;
  background: var(--accent); color: var(--accent-ink);
  padding: .6rem 1rem; border-radius: 0 0 10px 0; font-weight: 600;
}
.skip-link:focus { left: 0; }

/* ---------- header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.header-inner { display: flex; align-items: center; gap: 1.25rem; height: 62px; }
.brand { display: flex; align-items: center; gap: .6rem; text-decoration: none; color: var(--text); font-weight: 700; letter-spacing: -.01em; }
.brand-mark {
  width: 22px; height: 22px; border-radius: 7px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--accent) 14%, transparent);
}
.brand-name span { color: var(--accent); }
.site-nav { margin-left: auto; display: flex; gap: 1.4rem; font-size: .95rem; }
.site-nav a { color: var(--text-dim); text-decoration: none; }
.site-nav a:hover { color: var(--text); }
@media (max-width: 720px) { .site-nav { display: none; } }

.theme-toggle {
  margin-left: auto; width: 38px; height: 38px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface); cursor: pointer;
  display: grid; place-items: center;
}
.site-nav ~ .theme-toggle { margin-left: 0; }
.theme-icon {
  width: 16px; height: 16px; border-radius: 50%;
  background: var(--text-dim);
  box-shadow: inset -5px -3px 0 0 var(--surface);
}
html[data-theme="light"] .theme-icon { box-shadow: 0 0 0 2px var(--surface), 0 0 0 4px var(--text-dim); width: 10px; height: 10px; }

/* ---------- hero + tool ---------- */
.hero { padding: 3rem 0 2rem; background:
  radial-gradient(900px 380px at 50% -140px, color-mix(in srgb, var(--accent-2) 20%, transparent), transparent 70%); }
h1 {
  font-size: clamp(1.75rem, 4.4vw, 2.6rem);
  line-height: 1.15; letter-spacing: -.025em; margin: 0 0 .8rem;
  max-width: 22ch;
}
.lede { color: var(--text-dim); font-size: 1.06rem; max-width: 64ch; margin: 0 0 2rem; }

.tool {
  background: linear-gradient(180deg, var(--surface), var(--bg-soft));
  border: 1px solid var(--border);
  border-radius: 22px;
  padding: 1.6rem;
  box-shadow: var(--shadow);
}

.readout { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr); gap: 1.25rem; align-items: center; }
@media (max-width: 640px) { .readout { grid-template-columns: 1fr; } }

.bpm-block { text-align: center; }
.bpm {
  display: block;
  font-size: clamp(4rem, 16vw, 6.5rem);
  font-weight: 800; line-height: .92; letter-spacing: -.05em;
  font-variant-numeric: tabular-nums;
  background: linear-gradient(160deg, var(--text), var(--accent));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.bpm-meta { display: flex; align-items: baseline; justify-content: center; gap: .55rem; margin-top: .35rem; }
.bpm-unit { font-weight: 700; letter-spacing: .22em; font-size: .8rem; color: var(--text-dim); }
.bpm-precise { font-size: .8rem; color: var(--text-dim); font-variant-numeric: tabular-nums; }
.tempo-name { margin: .5rem 0 0; color: var(--accent); font-weight: 600; font-size: .95rem; min-height: 1.5em; }

.stats { display: grid; grid-template-columns: 1fr 1fr; gap: .6rem; margin: 0; }
.stat {
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: 12px; padding: .65rem .8rem;
}
.stat dt { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--text-dim); }
.stat dd { margin: .2rem 0 0; font-weight: 700; font-size: 1.05rem; font-variant-numeric: tabular-nums; }

/* tap pad */
.tap-pad {
  position: relative;
  display: grid; place-content: center; gap: .35rem;
  width: 100%; margin: 1.4rem 0 1.1rem;
  min-height: 190px;
  border: 1px solid color-mix(in srgb, var(--accent) 35%, var(--border));
  border-radius: 18px;
  background:
    radial-gradient(120% 120% at 50% 0%, color-mix(in srgb, var(--accent) 14%, transparent), transparent 60%),
    var(--surface-2);
  color: var(--text);
  cursor: pointer;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
  overflow: hidden;
  transition: transform .06s ease, border-color .15s ease, background-color .15s ease;
}
.tap-pad:hover { border-color: var(--accent); }
.tap-pad.is-hit { transform: scale(.988); }
.tap-label { font-size: 2.3rem; font-weight: 800; letter-spacing: .18em; }
.tap-hint { font-size: .85rem; color: var(--text-dim); letter-spacing: .01em; }
.tap-ring {
  position: absolute; inset: 50% auto auto 50%;
  width: 120px; height: 120px; margin: -60px 0 0 -60px;
  border-radius: 50%; border: 2px solid var(--accent);
  opacity: 0; pointer-events: none;
}
.tap-pad.is-hit .tap-ring { animation: ripple .5s ease-out; }
@keyframes ripple {
  from { opacity: .55; transform: scale(.35); }
  to   { opacity: 0;   transform: scale(2.4); }
}
.tap-pad.is-beat { background-color: color-mix(in srgb, var(--accent) 16%, var(--surface-2)); }
.tap-pad.is-accent { background-color: color-mix(in srgb, var(--accent-2) 22%, var(--surface-2)); }

kbd {
  font: inherit; font-size: .82em; padding: .05em .42em;
  border: 1px solid var(--border); border-bottom-width: 2px;
  border-radius: 5px; background: var(--surface); color: var(--text-dim);
}

/* controls */
.controls { display: flex; flex-wrap: wrap; gap: .6rem; align-items: center; }
.btn {
  display: inline-flex; align-items: center; gap: .5rem;
  padding: .62rem 1.05rem; border-radius: 11px;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text);
  font: inherit; font-size: .95rem; font-weight: 600; cursor: pointer;
  transition: background-color .15s ease, border-color .15s ease, transform .06s ease;
}
.btn:hover { border-color: var(--accent); }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--accent); color: var(--accent-ink); border-color: transparent; }
.btn-primary:hover { filter: brightness(1.06); }
.btn-lg { padding: .8rem 1.4rem; font-size: 1rem; text-decoration: none; }
.btn-icon { width: 42px; justify-content: center; padding: .62rem 0; font-size: 1.15rem; }
.nudge { display: flex; gap: .4rem; margin-left: auto; }
.metro-dot { width: 9px; height: 9px; border-radius: 50%; background: currentColor; opacity: .35; }
.btn-primary[aria-pressed="true"] .metro-dot { opacity: 1; animation: blink 1s steps(2, start) infinite; }
@keyframes blink { 50% { opacity: .2; } }

.options {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: .75rem; margin-top: 1.1rem; padding-top: 1.1rem; border-top: 1px solid var(--border);
}
.field { display: grid; gap: .3rem; font-size: .78rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: .06em; }
.field select, .field input[type="range"] {
  font: inherit; font-size: .92rem; text-transform: none; letter-spacing: normal;
  color: var(--text); background: var(--surface-2);
  border: 1px solid var(--border); border-radius: 9px; padding: .45rem .55rem; width: 100%;
}
.field input[type="range"] { padding: .35rem 0; accent-color: var(--accent); background: transparent; border: 0; }

/* ---------- prose ---------- */
.prose { padding: 3rem 0 1rem; max-width: 760px; }
.prose section { scroll-margin-top: 80px; }
.prose h2 {
  font-size: clamp(1.35rem, 2.8vw, 1.75rem); letter-spacing: -.02em;
  margin: 2.8rem 0 .8rem; padding-top: .2rem;
}
.prose section:first-child h2 { margin-top: 0; }
.prose h3 { font-size: 1.12rem; margin: 1.9rem 0 .5rem; letter-spacing: -.01em; }
.prose p { margin: 0 0 1rem; color: color-mix(in srgb, var(--text) 86%, var(--text-dim)); }
.prose strong { color: var(--text); }

.formula {
  background: var(--surface); border: 1px solid var(--border); border-left: 3px solid var(--accent);
  border-radius: 10px; padding: .9rem 1.1rem; font-weight: 700; color: var(--text) !important;
}

.checklist { list-style: none; padding: 0; margin: 0 0 1rem; display: grid; gap: .45rem; }
.checklist li { position: relative; padding-left: 1.6rem; color: var(--text-dim); }
.checklist li::before {
  content: ""; position: absolute; left: 0; top: .62em;
  width: 7px; height: 7px; border-radius: 50%; background: var(--accent);
}

.table-scroll { overflow-x: auto; margin: 0 0 1.2rem; }
table { width: 100%; border-collapse: collapse; font-size: .95rem; }
caption { text-align: left; color: var(--text-dim); font-size: .82rem; padding-bottom: .5rem; }
th, td { text-align: left; padding: .6rem .8rem; border-bottom: 1px solid var(--border); }
thead th { font-size: .78rem; text-transform: uppercase; letter-spacing: .07em; color: var(--text-dim); }
tbody tr:hover { background: var(--surface); }

.range-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); gap: .7rem; margin: 0 0 1.2rem; }
.range-card {
  display: grid; gap: .15rem; padding: .85rem .95rem;
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px;
}
.range-num { font-weight: 800; font-size: 1.15rem; font-variant-numeric: tabular-nums; }
.range-label { font-size: .8rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: .07em; }

.faq { display: grid; gap: .5rem; }
.faq details {
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 0 1rem;
}
.faq summary {
  cursor: pointer; padding: .9rem 0; font-weight: 600; list-style: none;
  display: flex; justify-content: space-between; align-items: center; gap: 1rem;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; color: var(--accent); font-size: 1.3rem; font-weight: 400; line-height: 1; }
.faq details[open] summary::after { content: "−"; }
.faq details p { margin: 0 0 1rem; color: var(--text-dim); }

.site-footer {
  margin-top: 3rem; padding: 2rem 0; border-top: 1px solid var(--border);
  color: var(--text-dim); font-size: .9rem; text-align: center;
}