:root {
  --ink: #3f3f3f;
  --muted: #797979;
  --paper: #fafafa;
  --white: #ffffff;
  --line: #e3e3e3;
  --secondary: #797979;
  --primary: #ea127e;
  --primary-soft: #fde2ef;
  --yellow: #f2d36b;
  --orange: #e9a45c;
  --shadow: 0 24px 60px rgba(24, 39, 31, .10);
  --radius: 22px;
  --max: 1180px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
}
a { color: inherit; text-decoration: none; }
.container { width: min(var(--max), calc(100% - 48px)); margin: 0 auto; }
.narrow { max-width: 820px; }
.section { padding: 112px 0 0; }

.site-header {
  position: sticky; top: 0; z-index: 20;
  background: rgba(247,248,244,.88);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(223,228,223,.8);
}
.nav-wrap { min-height: 76px; display: flex; align-items: center; justify-content: space-between; gap: 32px; }
.brand { display: inline-flex; align-items: center; gap: 11px; font-size: 20px; letter-spacing: -.02em; white-space: nowrap; }
.brand strong { font-weight: 800; }
.brand-mark {
  display: grid; grid-template-columns: repeat(3, 5px); gap: 2px;
  padding: 6px; border: 1.5px solid var(--secondary); border-radius: 8px;
}
.brand-mark span { width: 5px; height: 5px; background: var(--secondary); border-radius: 1px; }
.brand-mark.small { transform: scale(.82); transform-origin: left center; margin-right: -4px; }
.nav-links { display: flex; gap: 30px; color: #4e5a53; font-size: 16px; font-weight: 650; }
.nav-links a:hover, .text-link:hover { color: var(--primary); }
.menu-toggle { display: none; border: 0; background: none; padding: 6px; }
.menu-toggle span { display: block; width: 22px; height: 2px; margin: 4px; background: var(--ink); }

.hero {
  position: relative; overflow: hidden; min-height: 680px;
  background: var(--secondary); color: white; display: flex; align-items: center;
}
.hero-grid {
  position: absolute; inset: 0; opacity: .07;
  background-image: linear-gradient(rgba(255,255,255,.5) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.5) 1px, transparent 1px);
  background-size: 72px 72px;
  transform: perspective(500px) rotateX(25deg) scale(1.3);
  transform-origin: center bottom;
}
.hero::after {
  content: ""; position: absolute; width: 650px; height: 650px; border-radius: 50%;
  right: -260px; top: -280px; background: rgba(217,239,115,.08);
}
.hero-content { position: relative; z-index: 1; display: grid; grid-template-columns: 1fr .9fr; gap: 70px; align-items: center; padding: 80px 0; }
.eyebrow, .section-kicker, .card-label, .level {
  text-transform: uppercase; letter-spacing: .13em; font-weight: 800; font-size: 18px;
}
.eyebrow { display: flex; align-items: center; gap: 9px; color: var(--primary); margin: 0 0 22px; }
.eyebrow-dot { width: 7px; height: 7px; background: var(--primary); border-radius: 50%; }
.hero h1 { margin: 0; max-width: 680px; font-size: clamp(48px, 6vw, 78px); line-height: .98; letter-spacing: -.055em; }
.hero h1 span:first-of-type { color: var(--primary); }
.hero h1 span:last-of-type { display: block; }
.hero-text { max-width: 580px; margin: 28px 0; color: #ededed; font-size: 18px; line-height: 1.65; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; }
.button {
  display: inline-flex; align-items: center; justify-content: center; gap: 13px;
  min-height: 50px; padding: 0 21px; border-radius: 999px; font-size: 16px; font-weight: 800;
  transition: transform .2s ease, box-shadow .2s ease, background .2s ease;
}
.button:hover { transform: translateY(-2px); }
.button-primary { background: var(--primary); color: #17211b; box-shadow: 0 12px 25px rgba(0,0,0,.12); }
.button-secondary { border: 1px solid rgba(255,255,255,.28); color: white; }
.button-light { background: white; color: var(--secondary); }
.hero-note { margin-top: 20px; color: #d0d0d0; font-size: 16px; }
.check { color: var(--primary); font-weight: 900; }

.sudoku-hero { position: relative; width: min(440px, 100%); margin: auto; }
.hero-board {
  display: grid; grid-template-columns: repeat(9, 1fr); aspect-ratio: 1;
  background: white; padding: 6px; border-radius: 14px; overflow: hidden;
  box-shadow: 0 30px 80px rgba(0,0,0,.28); transform: rotate(2deg);
}
.cell {
  display: flex; align-items: center; justify-content: center;
  background: #f6f7f3; color: #666666; font-size: clamp(13px, 2.3vw, 21px); font-weight: 650;
  border-right: 1px solid #d9ded9; border-bottom: 1px solid #d9ded9;
}
.cell:nth-child(3n) { border-right: 2px solid #9fa9a1; }
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid #9fa9a1; }
.cell.filled { color: var(--secondary); background: #edf4dc; }
.floating-card {
  position: absolute; display: flex; align-items: center; gap: 11px; padding: 12px 16px;
  background: rgba(255,255,255,.96); color: var(--ink); border-radius: 13px;
  box-shadow: 0 16px 35px rgba(0,0,0,.22); font-size: 12px;
}
.floating-card strong, .floating-card small { display: block; line-height: 1.25; }
.floating-card small { color: var(--muted); margin-top: 3px; }
.floating-top { top: 10%; left: -45px; }
.floating-bottom { bottom: 8%; right: -42px; }
.mini-icon { width: 30px; height: 30px; display: grid; place-items: center; border-radius: 9px; background: var(--primary); color: var(--secondary); font-size: 17px; }
.mini-number { width: 30px; height: 30px; display: grid; place-items: center; border-radius: 9px; background: #eeeeee; color: var(--secondary); font-weight: 850; }

.intro { text-align: center; background: var(--paper); }
.section-kicker { color: var(--primary); margin: 0 0 14px; }
.intro h2, .section-heading h2, .learn-copy h2, .video-banner h2, .cta-inner h2 {
  margin: 0; font-size: clamp(36px, 4.3vw, 56px); line-height: 1.06; letter-spacing: -.045em;
}
.intro h2 em, .learn-copy h2 em { color: var(--primary); font-style: normal; }
.lead { max-width: 720px; margin: 26px auto 0; color: var(--muted); font-size: 17px; }

.techniques { background: white; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.section-heading { display: flex; justify-content: space-between; align-items: end; gap: 50px; margin-bottom: 45px; }
.section-heading > p { max-width: 430px; margin: 0; color: var(--muted); font-size: 15px; }
.technique-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.technique-card { min-height: 370px; padding: 26px; border: 1px solid var(--line); border-radius: var(--radius); display: flex; flex-direction: column; transition: transform .2s ease, box-shadow .2s ease; }
.technique-card:hover { transform: translateY(-5px); box-shadow: var(--shadow); }
.technique-card.beginner { background: #fdeaf3; }
.technique-card.intermediate { background: #f2f2f2; }
.technique-card.advanced { background: #ededed; }
.card-top { display: flex; justify-content: space-between; align-items: center; }
.level { color: #797979; }
.card-arrow { font-size: 20px; }
.technique-icon {
  width: 58px; height: 58px; margin: 50px 0 20px; border-radius: 15px; display: grid; place-items: center;
  background: white; color: var(--secondary); font-size: 23px; font-weight: 850; box-shadow: 0 8px 20px rgba(25,50,37,.08);
}
.technique-card h3 { margin: 0 0 9px; font-size: 24px; letter-spacing: -.03em; }
.technique-card p { color: var(--muted); font-size: 14px; margin: 0; }
.text-link { margin-top: auto; padding-top: 25px; color: var(--secondary); font-size: 16px; font-weight: 850; }
.text-link span { margin-left: 5px; }

.learn { background: var(--paper); }
.learn-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 90px; align-items: center; }
.learn-visual { position: relative; min-height: 430px; display: grid; place-items: center; }
.step-board { width: min(390px, 90%); aspect-ratio: 1; display: grid; grid-template-columns: repeat(9,1fr); padding: 5px; background: white; border: 1px solid var(--line); border-radius: 12px; box-shadow: var(--shadow); }
.step-cell { display: grid; place-items: center; color: #666666; background: #f9faf7; border-right: 1px solid #dfe4df; border-bottom: 1px solid #dfe4df; font-size: 14px; font-weight: 700; }
.step-cell.muted { background: #eeeeee; color: transparent; }
.step-cell.highlight { background: var(--primary); color: var(--secondary); box-shadow: inset 0 0 0 2px #a5bd45; }
.annotation { position: absolute; background: var(--secondary); color: white; padding: 8px 12px; border-radius: 999px; font-size: 11px; font-weight: 800; box-shadow: 0 8px 20px rgba(0,0,0,.13); }
.annotation-a { top: 17%; right: 4%; }
.annotation-b { bottom: 16%; left: 3%; }
.learn-copy > p:not(.section-kicker) { color: var(--muted); font-size: 16px; max-width: 530px; }
.feature-list { list-style: none; padding: 0; margin: 30px 0 0; display: grid; gap: 18px; }
.feature-list li { display: flex; gap: 13px; align-items: flex-start; }
.feature-list li > span { flex: 0 0 26px; width: 26px; height: 26px; display: grid; place-items: center; border-radius: 50%; background: #f8c7df; color: var(--secondary); font-size: 12px; font-weight: 900; }
.feature-list strong, .feature-list small { display: block; }
.feature-list strong { font-size: 14px; }
.feature-list small { color: var(--muted); font-size: 12px; margin-top: 2px; }

.knowledge { background: white; border-top: 1px solid var(--line); }
.knowledge-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.knowledge-card { min-height: 320px; border-radius: var(--radius); padding: 28px; display: flex; flex-direction: column; justify-content: space-between; }
.knowledge-card.history { background: #f4e0eb; }
.knowledge-card.facts { background: #f0f0f0; }
.knowledge-card.glossary { background: #e9e9e9; }
.knowledge-number { font-size: 12px; color: var(--primary); font-weight: 850; }
.card-label { color: var(--primary); margin: 0 0 12px; }
.knowledge-card h3 { margin: 0; font-size: 23px; line-height: 1.15; letter-spacing: -.025em; }
.knowledge-card p:not(.card-label) { color: var(--muted); font-size: 13px; }
.knowledge-card .text-link { display: inline-block; }

.videos { padding-top: 70px; padding-bottom: 70px; background: var(--secondary); color: white; }
.video-banner { display: flex; align-items: center; justify-content: space-between; gap: 40px; }
.video-banner .section-kicker { color: var(--primary); }
.video-banner h2 span { color: var(--primary); }
.video-banner p:not(.section-kicker) { color: #dddddd; max-width: 600px; margin: 15px 0 0; font-size: 15px; }

.final-cta { text-align: center; }
.cta-inner { display: flex; flex-direction: column; align-items: center; }
.cta-inner .button { margin-top: 30px; }

.site-footer { border-top: 1px solid var(--line); background: white; }
.footer-wrap { min-height: 100px; display: flex; align-items: center; justify-content: space-between; gap: 25px; color: var(--muted); font-size: 16px; }
.footer-wrap p { margin: 0; }

@media (max-width: 900px) {
  .hero-content, .learn-grid { grid-template-columns: 1fr; }
  .hero-content { gap: 55px; }
  .hero { min-height: auto; }
  .sudoku-hero { max-width: 400px; }
  .section-heading { align-items: start; flex-direction: column; gap: 18px; }
  .technique-grid, .knowledge-grid { grid-template-columns: 1fr; }
  .technique-card { min-height: 310px; }
  .learn-grid { gap: 55px; }
  .video-banner { flex-direction: column; align-items: flex-start; }
}

@media (max-width: 700px) {
  .container { width: min(var(--max), calc(100% - 30px)); }
  .section { padding: 78px 0 0 0; }
  .nav-links {
    display: none; position: absolute; left: 15px; right: 15px; top: 68px;
    padding: 18px; background: white; border: 1px solid var(--line); border-radius: 15px;
    box-shadow: var(--shadow); flex-direction: column; gap: 13px;
  }
  .nav-links.open { display: flex; }
  .menu-toggle { display: block; }
  .hero-content { padding: 70px 0 85px; }
  .hero h1 { font-size: clamp(45px, 14vw, 68px); }
  .hero-text { font-size: 16px; }
  .floating-top { left: -4px; top: 5%; }
  .floating-bottom { right: -3px; bottom: 4%; }
  .footer-wrap { padding: 25px 0; flex-wrap: wrap; }
}


.site-logo { width: 46px; height: 46px; display: block; object-fit: contain; flex: 0 0 auto; }
.footer-logo { width: 38px; height: 38px; }
.hero h1 span:first-of-type { color: var(--primary); }
.hero h1 span:last-of-type { color: #fff; }
.hero { background: var(--secondary); }
.hero::after { background: rgba(234,18,126,.16); }
.button-primary { background: var(--primary); color: #fff; }
.floating-card { border-top: 3px solid var(--primary); }
.mini-icon { background: var(--primary); color: #fff; }
.mini-number { background: #eeeeee; color: var(--primary); }
.hero-board .cell.filled { color: var(--primary); background: var(--primary-soft); }
.technique-icon { color: var(--primary); }
.technique-card:hover { border-color: rgba(234,18,126,.35); }
.step-cell.highlight { background: var(--primary-soft); color: var(--primary); box-shadow: inset 0 0 0 2px rgba(234,18,126,.5); }
.annotation { background: var(--primary); }
.videos { background: var(--secondary); }
.video-banner h2 span { color: var(--primary); }
.button-light { color: var(--primary); }

.site-logo { width: 46px; height: 46px; display: block; object-fit: contain; flex: 0 0 auto; }
.footer-logo { width: 38px; height: 38px; }
.subpage-hero { background: var(--secondary); color: white; padding: 105px 0 95px; }
.subpage-hero .section-kicker { color: var(--primary); }
.subpage-hero h1 { margin: 0; max-width: 820px; font-size: clamp(45px, 6vw, 72px); line-height: 1; letter-spacing: -.055em; }
.subpage-hero p:last-child { max-width: 650px; color: #dedede; font-size: 17px; margin: 24px 0 0; }
.subpage-content { max-width: 1050px; }
.subject-placeholder-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.page-note { color: var(--muted); text-align: center; margin: 35px 0 0; }
.video-coming-soon { min-height: 360px; display: grid; place-items: center; align-content: center; text-align: center; border: 1px solid var(--line); border-radius: var(--radius); background: #f7f7f7; padding: 40px; }
.video-coming-soon .mini-number { margin: 0 auto 20px; width: 54px; height: 54px; font-size: 20px; }
.video-coming-soon h2 { margin: 0; font-size: 36px; letter-spacing: -.04em; }
.video-coming-soon p { max-width: 550px; color: var(--muted); }
@media (max-width: 900px) { .subject-placeholder-grid { grid-template-columns: 1fr; } }