.frequency-hero {
  padding: 72px 6% 82px;
  background:
    radial-gradient(circle at 18% 15%, rgba(59,130,246,.25), transparent 34%),
    radial-gradient(circle at 84% 12%, rgba(14,165,233,.18), transparent 31%),
    linear-gradient(180deg, #0f172a 0%, #07111f 100%);
  color: #fff;
}

.frequency-hero__grid {
  max-width: 1240px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(0, .92fr) minmax(420px, 1.08fr);
  gap: 54px;
  align-items: center;
}

.frequency-kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 20px;
  padding: 9px 14px;
  border: 1px solid rgba(147,197,253,.24);
  border-radius: 999px;
  background: rgba(59,130,246,.13);
  color: #bfdbfe;
  font-size: 14px;
  font-weight: 800;
}

.frequency-hero h1 {
  margin: 0 0 24px;
  font-size: clamp(2.65rem, 5.2vw, 5.5rem);
  line-height: .98;
  letter-spacing: -.06em;
}

.frequency-hero__lead {
  max-width: 680px;
  color: rgba(255,255,255,.76);
  font-size: 1.16rem;
  line-height: 1.72;
}

.frequency-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 28px;
}

.frequency-pills span {
  padding: 9px 13px;
  border: 1px solid rgba(255,255,255,.12);
  border-radius: 999px;
  background: rgba(255,255,255,.07);
  color: rgba(255,255,255,.82);
  font-size: 13px;
  font-weight: 700;
}

.frequency-panel {
  border: 1px solid rgba(255,255,255,.13);
  border-radius: 30px;
  padding: 18px;
  background: rgba(255,255,255,.065);
  box-shadow: 0 34px 90px rgba(0,0,0,.32);
  backdrop-filter: blur(18px);
}

.frequency-panel__top {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 16px;
  align-items: center;
  margin-bottom: 14px;
}

.frequency-panel__label {
  color: #94a3b8;
  font-size: 12px;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: .08em;
}

.frequency-reference {
  display: flex;
  align-items: center;
  gap: 9px;
}

.frequency-reference label {
  color: #cbd5e1;
  font-size: 13px;
  font-weight: 700;
}

.frequency-reference select {
  appearance: none;
  min-width: 92px;
  padding: 9px 30px 9px 12px;
  border: 1px solid rgba(255,255,255,.16);
  border-radius: 12px;
  background: #0b1728;
  color: #fff;
  font: inherit;
  font-size: 14px;
  font-weight: 800;
}

.piano-scroll {
  overflow-x: auto;
  padding-bottom: 6px;
  scrollbar-width: thin;
  scrollbar-color: rgba(148,163,184,.45) transparent;
}

.piano-keyboard {
  position: relative;
  min-width: 980px;
  aspect-ratio: 5.2 / 1;
  border-radius: 16px;
  overflow: hidden;
  background: #dbe4ee;
  box-shadow: inset 0 0 0 1px rgba(15,23,42,.25);
}

.piano-white-keys {
  position: absolute;
  inset: 0;
  display: flex;
}

.piano-key {
  border: 0;
  cursor: pointer;
  transition: transform .12s ease, background-color .12s ease, box-shadow .12s ease;
}

.piano-key:focus-visible {
  outline: 3px solid #38bdf8;
  outline-offset: -3px;
}

.piano-key--white {
  flex: 1 1 0;
  min-width: 0;
  height: 100%;
  border-right: 1px solid #9aa7b6;
  background: linear-gradient(180deg, #fff 0%, #f8fafc 78%, #e2e8f0 100%);
  box-shadow: inset 0 -7px 10px rgba(15,23,42,.08);
}

.piano-key--white:hover,
.piano-key--white.is-selected {
  background: linear-gradient(180deg, #eff6ff 0%, #dbeafe 100%);
}

.piano-key--black {
  position: absolute;
  top: 0;
  z-index: 4;
  width: 1.16%;
  height: 61%;
  border-radius: 0 0 7px 7px;
  background: linear-gradient(180deg, #111827 0%, #020617 72%, #172033 100%);
  box-shadow: 0 7px 9px rgba(0,0,0,.35), inset 0 -5px 5px rgba(255,255,255,.05);
}

.piano-key--black:hover,
.piano-key--black.is-selected {
  background: linear-gradient(180deg, #2563eb 0%, #0f3f9c 100%);
}

.frequency-readout {
  display: grid;
  grid-template-columns: 1.1fr .9fr .9fr;
  gap: 10px;
  margin-top: 14px;
}

.frequency-readout__item {
  min-height: 78px;
  padding: 14px 16px;
  border: 1px solid rgba(255,255,255,.1);
  border-radius: 17px;
  background: rgba(15,23,42,.72);
}

.frequency-readout__item small {
  display: block;
  margin-bottom: 5px;
  color: #7f96af;
  font-size: 11px;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: .08em;
}

.frequency-readout__item strong {
  display: block;
  color: #fff;
  font-size: 1.1rem;
}

.frequency-readout__item:first-child strong {
  color: #93c5fd;
  font-size: 1.45rem;
}

.frequency-section {
  padding: 90px 6%;
  background: #fff;
}

.frequency-section--soft {
  background: #f7f9fc;
}

.frequency-section--dark {
  background:
    radial-gradient(circle at 16% 16%, rgba(37,99,235,.20), transparent 34%),
    linear-gradient(180deg, #0f172a 0%, #020617 100%);
  color: #fff;
}

.frequency-wrap {
  max-width: 1160px;
  margin: 0 auto;
}

.frequency-copy {
  max-width: 900px;
  margin: 0 auto;
}

.frequency-copy h2,
.frequency-center h2 {
  margin: 0 0 20px;
  color: #0f172a;
  font-size: clamp(2.1rem, 4vw, 3.75rem);
  line-height: 1.06;
  letter-spacing: -.045em;
}

.frequency-copy h3 {
  margin: 38px 0 12px;
  color: #0f172a;
  font-size: 1.42rem;
}

.frequency-copy p,
.frequency-copy li,
.frequency-center p {
  color: #475569;
  font-size: 1.07rem;
  line-height: 1.82;
}

.frequency-copy ul {
  padding-left: 22px;
}

.frequency-center {
  max-width: 830px;
  margin: 0 auto 44px;
  text-align: center;
}

.frequency-section--dark .frequency-center h2,
.frequency-section--dark .frequency-copy h2,
.frequency-section--dark .frequency-copy h3 {
  color: #fff;
}

.frequency-section--dark .frequency-center p,
.frequency-section--dark .frequency-copy p,
.frequency-section--dark .frequency-copy li {
  color: rgba(255,255,255,.72);
}

.reference-compare {
  margin: 28px 0 8px;
  overflow: hidden;
  border: 1px solid #dbe4ef;
  border-radius: 20px;
  background: #fff;
}

.reference-compare table {
  width: 100%;
  border-collapse: collapse;
}

.reference-compare th,
.reference-compare td {
  padding: 13px 16px;
  border-bottom: 1px solid #edf2f7;
  text-align: left;
  font-variant-numeric: tabular-nums;
}

.reference-compare th {
  background: #f8fafc;
  color: #475569;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: .05em;
}

.reference-compare td {
  color: #334155;
}

.reference-compare tr:last-child td {
  border-bottom: 0;
}

.frequency-formula {
  margin: 34px 0;
  padding: 26px;
  border: 1px solid #dbe4ef;
  border-radius: 24px;
  background: #f8fafc;
}

.frequency-formula__equation {
  margin-bottom: 12px;
  color: #0f172a;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: clamp(1.25rem, 3vw, 2rem);
  font-weight: 800;
}

.frequency-formula p {
  margin: 0;
  font-size: .98rem;
}

.frequency-octaves {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
  margin: 32px 0;
}

.frequency-octave {
  padding: 22px;
  border: 1px solid #e2e8f0;
  border-radius: 22px;
  background: #fff;
  box-shadow: 0 14px 36px rgba(15,23,42,.05);
}

.frequency-octave small {
  color: #64748b;
  font-weight: 700;
}

.frequency-octave strong {
  display: block;
  margin-top: 8px;
  color: #0f172a;
  font-size: 1.55rem;
}

.frequency-tool {
  margin-top: 40px;
  border: 1px solid #dce5ef;
  border-radius: 28px;
  overflow: hidden;
  background: #fff;
  box-shadow: 0 24px 70px rgba(15,23,42,.08);
}

.frequency-tool__bar {
  display: grid;
  grid-template-columns: minmax(220px, 1fr) auto;
  gap: 14px;
  align-items: end;
  padding: 20px;
  border-bottom: 1px solid #e2e8f0;
  background: #f8fafc;
}

.frequency-search label,
.frequency-table-ref label {
  display: block;
  margin-bottom: 7px;
  color: #475569;
  font-size: 12px;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: .06em;
}

.frequency-search input,
.frequency-table-ref select {
  width: 100%;
  min-height: 44px;
  box-sizing: border-box;
  border: 1px solid #cbd5e1;
  border-radius: 13px;
  background: #fff;
  color: #0f172a;
  padding: 10px 13px;
  font: inherit;
}

.frequency-table-ref select {
  min-width: 150px;
}

.frequency-table-scroll {
  max-height: 680px;
  overflow: auto;
}

.frequency-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}

.frequency-table th {
  position: sticky;
  top: 0;
  z-index: 2;
  padding: 12px 16px;
  background: #0f172a;
  color: #fff;
  text-align: left;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: .05em;
}

.frequency-table td {
  padding: 12px 16px;
  border-bottom: 1px solid #edf2f7;
  color: #475569;
}

.frequency-table tbody tr:hover,
.frequency-table tbody tr.is-selected {
  background: #eff6ff;
}

.frequency-table td strong {
  color: #0f172a;
}

.frequency-table__number {
  width: 68px;
}

.frequency-table__freq {
  font-variant-numeric: tabular-nums;
  font-weight: 800;
  color: #0f4ba8 !important;
}

.math-vs-real {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 22px;
  margin-top: 38px;
}

.math-card {
  padding: 30px;
  border: 1px solid rgba(255,255,255,.12);
  border-radius: 26px;
  background: rgba(255,255,255,.065);
}

.math-card h3 {
  margin: 0 0 12px;
  color: #fff;
  font-size: 1.35rem;
}

.math-card p {
  margin: 0;
  color: rgba(255,255,255,.7);
  line-height: 1.72;
}

.stretch-visual {
  margin-top: 42px;
  padding: 28px;
  border: 1px solid rgba(255,255,255,.12);
  border-radius: 28px;
  background: rgba(255,255,255,.055);
}

.stretch-visual svg {
  display: block;
  width: 100%;
  height: auto;
}

.related-frequency-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-top: 34px;
}

.related-frequency-card {
  display: block;
  padding: 27px;
  border: 1px solid rgba(255,255,255,.12);
  border-radius: 24px;
  background: rgba(255,255,255,.06);
  color: #fff;
  text-decoration: none;
  transition: transform .18s ease, background-color .18s ease, border-color .18s ease;
}

.related-frequency-card:hover {
  transform: translateY(-3px);
  background: rgba(255,255,255,.095);
  border-color: rgba(96,165,250,.35);
}

.related-frequency-card span {
  color: #93c5fd;
  font-size: 12px;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: .06em;
}

.related-frequency-card h3 {
  margin: 13px 0 9px;
  color: #fff;
  font-size: 1.28rem;
}

.related-frequency-card p {
  margin: 0;
  color: rgba(255,255,255,.68);
  line-height: 1.66;
}

.frequency-faq {
  display: grid;
  gap: 12px;
  max-width: 920px;
  margin: 0 auto;
}

.frequency-faq details {
  border: 1px solid #dbe4ef;
  border-radius: 18px;
  background: #fff;
  padding: 0 20px;
}

.frequency-faq summary {
  cursor: pointer;
  list-style: none;
  padding: 20px 30px 20px 0;
  color: #0f172a;
  font-size: 1rem;
  font-weight: 800;
}

.frequency-faq summary::-webkit-details-marker {
  display: none;
}

.frequency-faq p {
  margin: -2px 0 20px;
  color: #475569;
  line-height: 1.75;
}

.frequency-source-note {
  margin-top: 34px;
  padding-top: 24px;
  border-top: 1px solid #e2e8f0;
  color: #64748b;
  font-size: .92rem;
  line-height: 1.7;
}

.frequency-source-note a {
  color: #2563eb;
}

.frequency-cta {
  max-width: 920px;
  margin: 0 auto;
  text-align: center;
}

.frequency-cta h2 {
  margin: 0 0 18px;
  color: #fff;
  font-size: clamp(2.3rem, 4.5vw, 4.25rem);
  line-height: 1.03;
  letter-spacing: -.05em;
}

.frequency-cta p {
  max-width: 760px;
  margin: 0 auto 30px;
  color: rgba(255,255,255,.72);
  font-size: 1.1rem;
  line-height: 1.75;
}

@media (max-width: 980px) {
  .frequency-hero__grid,
  .math-vs-real,
  .related-frequency-grid {
    grid-template-columns: 1fr;
  }

  .frequency-panel {
    max-width: 760px;
  }

  .frequency-octaves {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 700px) {
  .frequency-hero,
  .frequency-section {
    padding-left: 5%;
    padding-right: 5%;
  }

  .frequency-panel__top,
  .frequency-tool__bar,
  .frequency-readout {
    grid-template-columns: 1fr;
  }

  .frequency-reference {
    justify-content: space-between;
  }

  .frequency-octaves {
    grid-template-columns: 1fr 1fr;
  }

  .frequency-table th,
  .frequency-table td {
    padding-left: 11px;
    padding-right: 11px;
  }
}

@media (max-width: 470px) {
  .frequency-octaves {
    grid-template-columns: 1fr;
  }
}