:root {
  --ink: #102a43;
  --ink-soft: #486581;
  --paper: #f7f9f7;
  --white: #ffffff;
  --navy: #102a43;
  --navy-2: #173f5f;
  --teal: #42c8c2;
  --teal-deep: #147d7a;
  --coral: #ff9f68;
  --yellow: #f7c948;
  --lavender: #9b8afb;
  --line: #dce6e9;
  --success: #1f9d78;
  --error: #c45742;
  --shadow: 0 20px 60px rgba(16, 42, 67, 0.1);
  --radius: 24px;
  --font-head: "Avenir Next", "Segoe UI", ui-sans-serif, system-ui, sans-serif;
  --font-body: Inter, "Segoe UI", ui-sans-serif, system-ui, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--font-body);
  line-height: 1.55;
}
button, input { font: inherit; }
button { color: inherit; }
:focus-visible { outline: 3px solid var(--yellow); outline-offset: 4px; }
[hidden] { display: none !important; }

.skip-link {
  position: fixed; left: 16px; top: -80px; z-index: 100;
  background: var(--white); color: var(--ink); padding: 12px 18px; border-radius: 8px;
}
.skip-link:focus { top: 16px; }

.site-header {
  position: sticky; top: 0; z-index: 40;
  height: 78px; padding: 0 clamp(20px, 4vw, 64px);
  display: flex; align-items: center; gap: 32px;
  background: rgba(247, 249, 247, .88); border-bottom: 1px solid rgba(16, 42, 67, .08);
  backdrop-filter: blur(18px);
}
.brand { display: inline-flex; align-items: center; gap: 11px; color: var(--ink); text-decoration: none; font-family: var(--font-head); font-size: 15px; white-space: nowrap; }
.brand strong { font-weight: 800; }
.brand-mark { width: 38px; height: 38px; border-radius: 12px; display: grid; place-items: center; background: var(--ink); color: white; }
.brand-mark svg { width: 30px; fill: none; stroke: var(--teal); stroke-width: 2.2; stroke-linecap: round; }
nav { display: flex; align-items: center; justify-content: center; gap: 8px; margin: auto; }
nav a { color: var(--ink-soft); text-decoration: none; font-weight: 600; font-size: 14px; padding: 10px 14px; border-radius: 999px; }
nav a:hover, nav a.active { color: var(--ink); background: var(--white); box-shadow: 0 3px 16px rgba(16, 42, 67, .07); }
.progress-pill { display: flex; align-items: center; gap: 9px; font-size: 12px; color: var(--ink-soft); font-weight: 600; }
.progress-ring { --progress: 0deg; width: 38px; height: 38px; border-radius: 50%; display: grid; place-items: center; background: conic-gradient(var(--teal) var(--progress), #dbe7e7 0); position: relative; }
.progress-ring::after { content: ""; position: absolute; inset: 4px; border-radius: inherit; background: var(--paper); }
.progress-ring span { position: relative; z-index: 1; font-size: 9px; color: var(--ink); }

.section { padding: 92px clamp(22px, 6vw, 96px); }
.card { background: var(--white); border: 1px solid rgba(16, 42, 67, .08); border-radius: var(--radius); box-shadow: var(--shadow); }
.hero { padding-top: 74px; overflow: hidden; }
.hero-grid { max-width: 1240px; margin: 0 auto 96px; display: grid; grid-template-columns: .86fr 1.14fr; align-items: center; gap: clamp(46px, 7vw, 100px); }
.eyebrow { max-width: 1240px; margin: 0 auto 24px; color: var(--teal-deep); text-transform: uppercase; letter-spacing: .16em; font-size: 12px; font-weight: 800; }
.eyebrow span { width: 24px; height: 2px; display: inline-block; vertical-align: middle; margin-right: 10px; background: var(--teal); }
h1, h2, h3 { font-family: var(--font-head); margin-top: 0; line-height: 1.1; letter-spacing: -.035em; }
h1 { font-size: clamp(46px, 6.6vw, 84px); margin-bottom: 26px; font-weight: 800; }
h1 em { color: var(--teal-deep); font-style: normal; }
.hero-lede { max-width: 590px; font-size: clamp(18px, 2vw, 22px); color: var(--ink-soft); margin: 0 0 34px; }
.hero-actions { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; }
.button { border: 0; border-radius: 14px; padding: 14px 20px; font-family: var(--font-head); font-weight: 750; cursor: pointer; transition: transform .2s ease, box-shadow .2s ease, background .2s ease; }
.button:hover:not(:disabled) { transform: translateY(-2px); }
.button-primary { background: var(--ink); color: white; box-shadow: 0 10px 24px rgba(16, 42, 67, .18); }
.button-primary:hover:not(:disabled) { background: var(--navy-2); box-shadow: 0 14px 28px rgba(16, 42, 67, .23); }
.button-secondary { background: #e9f2f2; color: var(--ink); }
.button:disabled { opacity: .45; cursor: not-allowed; }
.microcopy { color: #829ab1; font-size: 12px; }

.hero-visual { padding: 20px 22px 22px; position: relative; transform: rotate(1deg); }
.hero-visual::before { content: ""; position: absolute; width: 160px; height: 160px; right: -55px; top: -55px; background: #d7f4f2; border-radius: 50%; z-index: -1; }
.visual-toolbar, .trainer-topline, .trace-meta, .quiz-status { display: flex; justify-content: space-between; align-items: center; gap: 16px; color: var(--ink-soft); font-size: 12px; font-weight: 650; }
.live-badge { display: flex; align-items: center; gap: 7px; }
.live-badge i { width: 7px; height: 7px; border-radius: 50%; background: var(--coral); box-shadow: 0 0 0 5px rgba(255, 159, 104, .18); }
.hero-wave { width: 100%; overflow: visible; }
.grid-lines path, .trace-grid path { stroke: #dfe9ea; stroke-width: 1; fill: none; }
.wave-path { stroke: var(--teal-deep); stroke-width: 3; fill: none; stroke-linecap: round; vector-effect: non-scaling-stroke; }
.animated-wave { stroke: url(#waveGlow); stroke-width: 4; stroke-dasharray: 15 5; animation: trace-flow 4s linear infinite; }
@keyframes trace-flow { to { stroke-dashoffset: -100; } }
.time-bracket { fill: none; stroke: #9fb3c8; stroke-width: 1.5; }
.hero-wave text, #practice-wave text { font-family: var(--font-body); font-size: 11px; fill: #829ab1; }
.visual-answer { display: flex; align-items: center; justify-content: center; gap: clamp(10px, 2vw, 24px); padding-top: 10px; }
.visual-answer div { display: grid; text-align: center; }
.visual-answer strong { font-family: var(--font-head); font-size: 25px; line-height: 1; }
.visual-answer span { color: var(--ink-soft); font-size: 11px; }
.visual-answer .equals { color: #9fb3c8; font-size: 18px; }
.visual-answer .result { background: #e5f7f6; border-radius: 12px; padding: 9px 16px; }
.visual-answer .result strong { color: var(--teal-deep); }

.lesson-panel { max-width: 1240px; margin: 0 auto; scroll-margin-top: 96px; }
.section-heading { display: flex; justify-content: space-between; align-items: end; gap: 42px; margin-bottom: 38px; }
.section-heading h2 { font-size: clamp(35px, 5vw, 58px); margin: 8px 0 0; }
.section-heading p { max-width: 430px; margin: 0; color: var(--ink-soft); font-size: 17px; }
.step-label, .mini-label, .challenge-kicker, .quiz-category { color: var(--teal-deep); text-transform: uppercase; letter-spacing: .16em; font-size: 11px; font-weight: 800; }
.formula-strip { display: flex; justify-content: center; align-items: center; gap: clamp(8px, 2.3vw, 32px); margin-bottom: 28px; padding: 16px 22px; border: 1px dashed #a9d8d5; background: #edf9f8; border-radius: 16px; font-family: var(--font-head); font-size: clamp(12px, 1.7vw, 17px); font-weight: 700; text-align: center; }
.formula-strip strong { font-size: 22px; color: var(--teal-deep); }
.band-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
.band-card { --band: var(--teal); min-height: 200px; padding: 24px; display: flex; flex-direction: column; align-items: flex-start; justify-content: flex-end; gap: 3px; border: 1px solid var(--line); background: white; border-radius: 20px; cursor: pointer; text-align: left; transition: transform .2s, box-shadow .2s, border-color .2s; position: relative; overflow: hidden; }
.band-card::after { content: ""; width: 100px; height: 100px; position: absolute; right: -40px; top: -40px; border-radius: 50%; background: color-mix(in srgb, var(--band) 18%, white); transition: transform .25s; }
.band-card:hover, .band-card.active { transform: translateY(-5px); border-color: var(--band); box-shadow: 0 16px 30px rgba(16, 42, 67, .1); }
.band-card:hover::after, .band-card.active::after { transform: scale(1.4); }
.band-icon { position: absolute; top: 20px; left: 22px; width: 40px; height: 40px; border-radius: 12px; display: grid; place-items: center; background: color-mix(in srgb, var(--band) 22%, white); color: var(--ink); font-family: serif; font-size: 23px; }
.band-card.theta { --band: var(--yellow); }
.band-card.alpha { --band: var(--coral); }
.band-card.beta { --band: var(--lavender); }
.band-name { color: var(--ink-soft); font-size: 13px; font-weight: 700; }
.band-card strong { font-family: var(--font-head); font-size: 28px; }
.band-card small { color: #829ab1; }

.frequency-lab { margin-top: 18px; padding: 34px; display: grid; grid-template-columns: .7fr 1.3fr; gap: 46px; align-items: center; background: var(--ink); color: white; overflow: hidden; }
.lab-copy h3 { font-size: 28px; margin: 8px 0 8px; }
.lab-copy p { margin: 0 0 26px; color: #bcccdc; }
.lab-copy label { display: flex; align-items: center; justify-content: space-between; font-size: 13px; font-weight: 700; }
.lab-copy output { color: var(--teal); font-family: var(--font-head); font-size: 24px; }
input[type="range"] { width: 100%; height: 7px; margin-top: 15px; appearance: none; border-radius: 10px; background: linear-gradient(90deg, var(--teal) var(--range, 9%), #39566f var(--range, 9%)); }
input[type="range"]::-webkit-slider-thumb { appearance: none; width: 23px; height: 23px; border-radius: 50%; background: white; border: 5px solid var(--teal); cursor: grab; }
.range-labels { display: flex; justify-content: space-between; color: #829ab1; font-size: 10px; margin-top: 6px; }
.lab-visual { min-width: 0; position: relative; }
.lab-visual .grid-lines path { stroke: #274861; }
.lab-visual .wave-path { stroke: var(--teal); }
.current-band { position: absolute; z-index: 2; left: 22px; top: 20px; display: flex; align-items: center; gap: 10px; }
.current-band span { width: 36px; height: 36px; display: grid; place-items: center; background: rgba(66, 200, 194, .15); color: var(--teal); border-radius: 10px; font-size: 21px; font-family: serif; }
.lab-visual svg { width: 100%; min-height: 210px; }
.lab-visual p { margin: 0; min-height: 50px; color: #bcccdc; font-size: 13px; }
.key-rule { display: flex; align-items: center; gap: 18px; margin-top: 18px; padding: 20px 24px; border: 1px solid #eadca7; background: #fffaf0; border-radius: 16px; }
.key-rule p { margin: 0; }
.rule-icon { flex: 0 0 34px; width: 34px; height: 34px; display: grid; place-items: center; border-radius: 50%; background: var(--yellow); font-weight: 800; }

.practice { background: var(--ink); color: white; }
.section-heading.light { max-width: 1240px; margin-left: auto; margin-right: auto; }
.section-heading.light p { color: #bcccdc; }
.practice .step-label { color: var(--teal); }
.method-row { max-width: 1100px; margin: 0 auto 28px; display: flex; align-items: center; justify-content: center; gap: clamp(8px, 2vw, 22px); color: #d9e2ec; font-size: 13px; font-weight: 600; }
.method-row span { display: flex; align-items: center; gap: 8px; white-space: nowrap; }
.method-row i { width: 24px; height: 24px; display: grid; place-items: center; border-radius: 50%; background: #274861; color: var(--teal); font-style: normal; font-size: 11px; }
.method-row b { color: #486581; }
.trainer { max-width: 1240px; margin: 0 auto; color: var(--ink); padding: 24px; }
.trainer-topline { margin-bottom: 14px; }
.trainer-topline > div { display: flex; gap: 12px; align-items: center; }
.trainer-topline strong { color: var(--ink); }
.score-chip { padding: 7px 12px; border-radius: 999px; background: #edf9f8; color: var(--teal-deep); }
.score-chip span { font-weight: 800; }
.meter { height: 4px; background: #edf1f2; border-radius: 99px; overflow: hidden; margin-bottom: 25px; }
.meter span { display: block; width: 8%; height: 100%; background: linear-gradient(90deg, var(--teal), var(--coral)); transition: width .35s ease; }
.challenge-grid { display: grid; grid-template-columns: 1.18fr .82fr; border: 1px solid var(--line); border-radius: 19px; overflow: hidden; min-height: 455px; }
.trace-panel { padding: 22px; background: #f3f7f7; }
.icon-button, .text-button { border: 0; background: none; cursor: pointer; color: var(--teal-deep); font-size: 12px; font-weight: 700; }
.icon-button { padding: 8px 10px; border-radius: 9px; }
.icon-button:hover, .icon-button[aria-pressed="true"] { background: #dff3f1; }
#practice-wave { width: 100%; margin-top: 24px; }
.practice-wave-path { fill: none; stroke: var(--ink); stroke-width: 3.3; stroke-linecap: round; stroke-linejoin: round; vector-effect: non-scaling-stroke; }
.practice-bracket { stroke: var(--coral); stroke-width: 2; }
.cycle-guides line { stroke: var(--coral); stroke-width: 1.5; stroke-dasharray: 5 5; }
.cycle-guides circle { fill: var(--coral); }
.trace-legend { display: flex; gap: 24px; color: #829ab1; font-size: 11px; }
.trace-legend span { display: flex; align-items: center; gap: 7px; }
.legend-wave { width: 20px; height: 2px; background: var(--ink); }
.legend-time { width: 20px; border-top: 2px dashed var(--coral); }
.question-panel { padding: clamp(26px, 4vw, 48px); display: flex; flex-direction: column; justify-content: center; }
.question-panel h3, .quiz-live h3 { font-size: clamp(24px, 3vw, 34px); margin: 10px 0 12px; }
.challenge-hint { color: var(--ink-soft); margin: 0 0 24px; }
.answer-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; }
.answer-option, .quiz-option { border: 1px solid var(--line); background: white; border-radius: 12px; padding: 13px 16px; text-align: left; cursor: pointer; font-weight: 700; transition: .18s; }
.answer-option:hover, .quiz-option:hover { border-color: var(--teal); background: #f4fbfa; }
.answer-option.correct, .quiz-option.correct { border-color: var(--success); background: #e9f8f2; color: #12654e; }
.answer-option.incorrect, .quiz-option.incorrect { border-color: var(--error); background: #fff0ed; color: #9b3f2e; }
.answer-option:disabled, .quiz-option:disabled { cursor: default; }
.feedback { display: flex; gap: 12px; align-items: flex-start; margin-top: 18px; padding: 14px; border-radius: 12px; background: #f0f7f7; }
.feedback.good { background: #e9f8f2; }
.feedback.try { background: #fff3eb; }
.feedback-icon { flex: 0 0 26px; height: 26px; border-radius: 50%; display: grid; place-items: center; color: white; font-size: 13px; background: var(--teal-deep); }
.feedback p { margin: 2px 0 0; color: var(--ink-soft); font-size: 13px; }
.next-button { align-self: flex-start; margin-top: 18px; }
.coach-note { max-width: 850px; margin: 26px auto 0; display: flex; align-items: center; justify-content: center; gap: 15px; color: #d9e2ec; font-size: 13px; }
.coach-note p { margin: 0; }
.coach-avatar { flex: 0 0 38px; height: 38px; display: grid; place-items: center; border-radius: 50%; background: var(--coral); color: var(--ink); font-weight: 900; font-size: 11px; }

.knowledge { max-width: 1432px; margin: 0 auto; }
.quiz-shell { max-width: 1040px; min-height: 440px; margin: 0 auto; padding: clamp(28px, 5vw, 60px); display: grid; align-items: center; }
.quiz-intro, .quiz-results { display: grid; grid-template-columns: 260px 1fr; align-items: center; gap: clamp(35px, 7vw, 90px); }
.quiz-intro h3, .quiz-results h3 { margin: 10px 0; font-size: clamp(27px, 4vw, 42px); }
.quiz-intro p, .quiz-results p { color: var(--ink-soft); margin: 0 0 24px; max-width: 560px; }
.quiz-illustration, .result-gauge { width: 230px; height: 230px; position: relative; border-radius: 50%; display: grid; place-content: center; text-align: center; background: #e8f7f5; }
.quiz-illustration::before { content: ""; position: absolute; inset: 34px; border-radius: 50%; background: white; }
.quiz-illustration strong, .quiz-illustration small { position: relative; z-index: 1; }
.quiz-illustration strong { font-family: var(--font-head); font-size: 62px; line-height: 1; }
.quiz-illustration small { color: var(--ink-soft); }
.orbit { position: absolute; inset: -8px; border: 2px dashed var(--teal); border-radius: 48% 52% 51% 49%; animation: spin 14s linear infinite; }
.orbit-two { inset: 15px -15px; border-color: var(--coral); animation-direction: reverse; animation-duration: 18s; }
@keyframes spin { to { transform: rotate(360deg); } }
.quiz-live { max-width: 780px; width: 100%; margin: auto; }
.quiz-dots { display: flex; gap: 6px; }
.quiz-dots span { width: 28px; height: 5px; border-radius: 9px; background: #dce6e9; }
.quiz-dots span.current { background: var(--teal); }
.quiz-dots span.done { background: var(--teal-deep); }
.quiz-category { margin: 44px 0 0; }
.quiz-options { display: grid; gap: 10px; margin: 28px 0 24px; }
.quiz-option { padding: 15px 18px; display: flex; gap: 12px; align-items: center; }
.quiz-option span { width: 27px; height: 27px; flex: 0 0 27px; display: grid; place-items: center; border-radius: 8px; background: #eff3f4; font-size: 12px; }
.quiz-option.selected { border-color: var(--teal-deep); background: #edf9f8; }
.result-gauge { --score-angle: 0deg; background: conic-gradient(var(--teal) var(--score-angle), #e5ecee 0); }
.result-gauge::after { content: ""; position: absolute; inset: 17px; background: white; border-radius: 50%; }
.result-gauge strong, .result-gauge span { position: relative; z-index: 1; }
.result-gauge strong { font-family: var(--font-head); font-size: 46px; line-height: 1.1; }
.result-gauge span { color: var(--ink-soft); }
.result-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.course-complete { max-width: 1040px; margin: 18px auto 0; padding: 18px 22px; display: flex; align-items: center; gap: 16px; background: #e8f7f5; border: 1px solid #b8e7e3; border-radius: 16px; }
.course-complete > span { width: 38px; height: 38px; display: grid; place-items: center; border-radius: 50%; background: var(--teal-deep); color: white; font-weight: 800; }
.course-complete p { margin: 1px 0 0; color: var(--ink-soft); font-size: 13px; }

footer { padding: 35px clamp(22px, 6vw, 96px); display: flex; align-items: center; justify-content: space-between; gap: 34px; border-top: 1px solid var(--line); background: white; }
footer p { max-width: 690px; color: var(--ink-soft); font-size: 11px; text-align: center; }
.footer-brand .brand-mark { width: 30px; height: 30px; border-radius: 9px; }

@media (max-width: 980px) {
  .site-header nav { display: none; }
  .progress-pill { margin-left: auto; }
  .hero-grid { grid-template-columns: 1fr; }
  .hero-copy { text-align: center; }
  .hero-lede { margin-left: auto; margin-right: auto; }
  .hero-actions { justify-content: center; }
  .hero-visual { max-width: 720px; width: 100%; margin: 0 auto; }
  .band-grid { grid-template-columns: repeat(2, 1fr); }
  .frequency-lab, .challenge-grid { grid-template-columns: 1fr; }
  .trace-panel { min-height: 390px; }
}

@media (max-width: 680px) {
  .section { padding: 68px 18px; }
  .hero { padding-top: 44px; }
  .hero-grid { margin-bottom: 70px; }
  .eyebrow { text-align: center; }
  .site-header { height: 68px; padding: 0 16px; }
  .progress-label { display: none; }
  .section-heading { display: block; }
  .section-heading p { margin-top: 14px; }
  .band-grid { grid-template-columns: 1fr 1fr; gap: 9px; }
  .band-card { min-height: 170px; padding: 18px; }
  .band-card strong { font-size: 23px; }
  .formula-strip { gap: 5px; padding: 12px 8px; }
  .method-row { display: grid; grid-template-columns: 1fr 1fr; }
  .method-row b { display: none; }
  .trainer { padding: 10px; border-radius: 18px; }
  .trainer-topline { padding: 8px; }
  .trace-panel { min-height: auto; padding: 14px; }
  .question-panel { padding: 26px 18px; }
  .answer-grid { grid-template-columns: 1fr 1fr; }
  .quiz-intro, .quiz-results { grid-template-columns: 1fr; text-align: center; }
  .quiz-illustration, .result-gauge { width: 175px; height: 175px; margin: 0 auto; }
  .quiz-illustration strong { font-size: 45px; }
  .quiz-intro p, .quiz-results p { margin-left: auto; margin-right: auto; }
  .result-actions { justify-content: center; }
  footer { flex-direction: column; text-align: center; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
}