*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; min-width: 320px; font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; background: var(--brand-canvas); color: var(--brand-ink); }
a { color: inherit; }
button, select { font: inherit; }
::selection { background: var(--brand-active); }
:focus-visible { outline: 3px solid var(--brand-accent); outline-offset: 3px; }
.page-shell { min-height: 100vh; overflow: hidden; background: radial-gradient(circle at 83% 8%, var(--brand-active), transparent 35%), var(--brand-canvas); }
.site-header, main, .site-footer { width: min(1180px, calc(100% - 48px)); margin-inline: auto; }
.site-header { min-height: 88px; display: flex; align-items: center; justify-content: space-between; gap: 20px; border-bottom: 1px solid var(--brand-line); }
.wordmark { flex: 0 0 auto; font-size: 19px; font-weight: 820; letter-spacing: -.06em; text-decoration: none; }
.wordmark span { margin-left: 5px; color: var(--brand-accent); }
.site-nav { display: flex; align-items: center; gap: 22px; }
.site-nav a { color: var(--brand-muted); font-size: 13px; font-weight: 700; text-decoration: none; }
.site-nav a:hover, .site-nav a[aria-current="page"] { color: var(--brand-accent); }
.header-actions { display: flex; align-items: center; gap: 16px; }
.theme-label { color: var(--brand-muted); font-size: 13px; }
#theme-select { appearance: none; min-height: 38px; max-width: 162px; padding: 7px 28px 7px 11px; border: 1px solid var(--brand-line); border-radius: 9px; background: var(--brand-surface) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6' viewBox='0 0 10 6'%3E%3Cpath d='m1 1 4 4 4-4' fill='none' stroke='%23818b96' stroke-width='1.5'/%3E%3C/svg%3E") no-repeat right 11px center; color: var(--brand-ink); font-size: 13px; cursor: pointer; }
.header-link { font-size: 13px; font-weight: 700; white-space: nowrap; text-decoration-thickness: 1px; text-underline-offset: 4px; }
.header-link span { color: var(--brand-accent); }
.hero { display: grid; grid-template-columns: minmax(0, 1fr) minmax(370px, .93fr); align-items: center; gap: 40px; min-height: 610px; padding: 78px 0 98px; }
.hero-copy { position: relative; z-index: 1; }
.eyebrow { display: flex; align-items: center; gap: 9px; margin: 0 0 27px; color: var(--brand-accent); font-size: 12px; font-weight: 800; letter-spacing: .15em; text-transform: uppercase; }
.eyebrow-mark { width: 8px; height: 8px; border-radius: 50%; background: currentColor; box-shadow: 0 0 0 5px var(--brand-active); }
h1, h2, h3, p { margin-top: 0; }
h1 { max-width: 650px; margin-bottom: 26px; font-size: clamp(47px, 5.8vw, 82px); line-height: 1.05; font-weight: 760; letter-spacing: -.065em; }
h1 em { color: var(--brand-accent); font-style: normal; }
.hero-description { max-width: 520px; margin-bottom: 33px; color: var(--brand-muted); font-size: clamp(17px, 1.8vw, 20px); line-height: 1.65; }
.hero-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 16px 20px; }
.button-primary, .button-secondary { display: inline-flex; align-items: center; justify-content: center; gap: 26px; min-height: 52px; padding: 0 23px; border-radius: 13px; font-size: 15px; font-weight: 760; text-decoration: none; transition: transform .16s ease, box-shadow .16s ease, background .16s ease; }
.button-primary { background: var(--brand-accent); color: var(--brand-canvas); box-shadow: 0 13px 24px color-mix(in srgb, var(--brand-accent) 20%, transparent); }
.button-primary:hover { transform: translateY(-2px); box-shadow: 0 17px 26px color-mix(in srgb, var(--brand-accent) 28%, transparent); }
.action-note { max-width: 190px; color: var(--brand-muted); font-size: 12px; line-height: 1.5; }
.text-link { color: var(--brand-accent); font-size: 14px; font-weight: 700; text-underline-offset: 4px; }
.hero-art { position: relative; display: grid; place-items: center; min-height: 440px; }
.art-halo { position: absolute; width: min(100%, 480px); aspect-ratio: 1; border: 1px solid var(--brand-line); border-radius: 50%; background: radial-gradient(circle at center, var(--brand-active), transparent 70%); box-shadow: 0 0 0 38px color-mix(in srgb, var(--brand-line) 35%, transparent), 0 0 0 76px color-mix(in srgb, var(--brand-line) 17%, transparent); }
.board-preview { position: relative; width: min(100%, 510px); height: 340px; transform: rotate(-4deg); border: 1px solid var(--brand-line); border-radius: 20px; background: var(--brand-surface); box-shadow: 0 22px 60px color-mix(in srgb, var(--brand-ink) 13%, transparent); overflow: hidden; }
.preview-toolbar { height: 52px; display: flex; align-items: center; gap: 8px; padding: 0 18px; border-bottom: 1px solid var(--brand-line); background: var(--brand-tint); }
.preview-toolbar span { width: 8px; height: 8px; border-radius: 50%; background: var(--brand-line); }
.preview-toolbar span:first-child { background: var(--brand-accent); opacity: .65; }
.preview-toolbar i { width: 105px; height: 13px; margin-left: 22px; border-radius: 5px; background: var(--brand-line); opacity: .7; }
.preview-content { position: relative; height: calc(100% - 52px); padding: 33px 40px; background-image: linear-gradient(var(--brand-grid) 1px, transparent 1px), linear-gradient(90deg, var(--brand-grid) 1px, transparent 1px); background-size: 30px 30px; }
.preview-chip { display: inline-block; padding: 7px 10px; border: 1px solid var(--brand-line); border-radius: 7px; background: var(--brand-surface); color: var(--brand-muted); font-size: 11px; font-weight: 700; }
.preview-equation { margin-top: 28px; color: var(--brand-ink); font-family: Georgia, serif; font-size: clamp(27px, 3vw, 38px); font-style: italic; letter-spacing: .015em; }
.preview-steps { margin-top: 20px; margin-left: 27px; color: var(--brand-muted); font-family: Georgia, serif; font-size: 25px; font-style: italic; }
.preview-answer { margin-top: 19px; margin-left: 42px; color: var(--brand-accent); font-family: Georgia, serif; font-size: 24px; font-style: italic; }
.preview-stroke { position: absolute; right: 14px; bottom: 10px; width: 190px; color: var(--brand-accent); opacity: .6; }
.floating-note { position: absolute; right: -18px; bottom: 28px; display: flex; align-items: center; gap: 9px; padding: 13px 17px; border: 1px solid var(--brand-line); border-radius: 12px; background: var(--brand-surface); box-shadow: var(--brand-shadow); color: var(--brand-ink); font-size: 12px; font-weight: 650; transform: rotate(3deg); }
.note-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--brand-accent); }
.product-section { padding: 10px 0 95px; }
.section-intro { display: grid; grid-template-columns: 1.1fr .9fr; gap: 38px; align-items: end; margin-bottom: 31px; }
.section-intro .eyebrow { grid-column: 1 / -1; margin-bottom: -20px; }
.section-intro h2 { max-width: 650px; margin-bottom: 0; font-size: clamp(32px, 3.5vw, 47px); line-height: 1.14; letter-spacing: -.05em; }
.section-intro > p:last-child { margin-bottom: 3px; color: var(--brand-muted); font-size: 15px; line-height: 1.7; }
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.feature-card { min-height: 215px; padding: 24px 23px; border: 1px solid var(--brand-line); border-radius: 17px; background: var(--brand-tint); box-shadow: var(--brand-shadow); }
.feature-icon { display: grid; place-items: center; width: 36px; height: 36px; margin-bottom: 26px; border-radius: 9px; background: var(--brand-active); color: var(--brand-accent); font-size: 22px; }
.feature-card h3 { margin-bottom: 10px; font-size: 18px; letter-spacing: -.02em; }
.feature-card p { margin-bottom: 0; color: var(--brand-muted); font-size: 14px; line-height: 1.65; }
.details-section { display: grid; grid-template-columns: 1fr 1fr; gap: 36px; margin: 0 0 44px; padding: 34px 0; border-top: 1px solid var(--brand-line); }
.details-section .eyebrow { margin-bottom: 16px; }
.details-section h2, .premium-section h2 { margin-bottom: 0; font-size: clamp(27px, 3vw, 38px); letter-spacing: -.045em; }
.details-section > p { align-self: end; max-width: 520px; margin-bottom: 0; color: var(--brand-muted); font-size: 15px; line-height: 1.7; }
.premium-section { margin-bottom: 55px; padding: 30px 32px; border: 1px solid var(--brand-line); border-radius: 17px; background: var(--brand-tint); }
.premium-section .eyebrow { margin-bottom: 14px; }
.premium-section p:last-child { max-width: 760px; margin: 14px 0 0; color: var(--brand-muted); font-size: 14px; line-height: 1.65; }
.closing { display: flex; align-items: center; gap: 24px; margin-bottom: 75px; padding: 28px 31px; border: 1px solid var(--brand-line); border-radius: 19px; background: var(--brand-surface); box-shadow: var(--brand-shadow); }
.closing img { flex: 0 0 auto; width: 68px; height: 68px; padding: 10px; border-radius: 13px; background: #fff; }
.closing h2 { margin-bottom: 4px; font-size: 23px; letter-spacing: -.03em; }
.closing p { margin-bottom: 0; color: var(--brand-muted); font-size: 14px; line-height: 1.5; }
.button-secondary { min-height: 45px; margin-left: auto; border: 1px solid var(--brand-accent); color: var(--brand-accent); white-space: nowrap; }
.button-secondary:hover { transform: translateY(-2px); background: var(--brand-hover); }
.site-footer { display: flex; justify-content: space-between; gap: 20px; padding: 22px 0 34px; border-top: 1px solid var(--brand-line); color: var(--brand-muted); font-size: 12px; }
.site-footer span:first-child { color: var(--brand-ink); font-weight: 750; }
.site-footer nav { display: flex; flex-wrap: wrap; gap: 18px; }
.site-footer a { text-underline-offset: 3px; }
@media (max-width: 980px) {
  .hero { grid-template-columns: 1fr; gap: 8px; padding-top: 70px; }
  .hero-art { min-height: 390px; margin: 0 35px; }
  .section-intro { grid-template-columns: 1fr; gap: 12px; }
  .section-intro .eyebrow { margin-bottom: 0; }
  .details-section { grid-template-columns: 1fr; gap: 14px; }
}
@media (max-width: 650px) {
  .site-header, main, .site-footer { width: min(100% - 32px, 1180px); }
  .site-header { min-height: 74px; flex-wrap: wrap; gap: 7px 12px; padding: 12px 0; }
  .wordmark { font-size: 17px; }
  .site-nav { order: 3; width: 100%; gap: 22px; }
  .site-nav a { font-size: 12px; }
  .header-actions { gap: 9px; }
  .theme-label, .header-link { display: none; }
  #theme-select { max-width: 148px; font-size: 12px; }
  .hero { min-height: auto; padding: 58px 0 70px; }
  .eyebrow { margin-bottom: 22px; font-size: 10px; }
  h1 { font-size: clamp(44px, 12vw, 62px); }
  .hero-description { font-size: 16px; }
  .hero-actions { align-items: flex-start; flex-direction: column; }
  .action-note { max-width: none; }
  .hero-art { min-height: 310px; margin: 18px 2px 0; }
  .board-preview { height: 270px; }
  .preview-content { padding: 21px 23px; }
  .preview-equation { margin-top: 20px; font-size: 27px; }
  .preview-steps { margin-top: 15px; margin-left: 15px; font-size: 19px; }
  .preview-answer { margin-top: 15px; margin-left: 22px; font-size: 18px; }
  .preview-stroke { width: 140px; }
  .floating-note { right: -4px; bottom: 0; font-size: 11px; }
  .product-section { padding-bottom: 60px; }
  .feature-grid { grid-template-columns: 1fr; }
  .feature-card { min-height: 0; }
  .feature-icon { margin-bottom: 17px; }
  .closing { flex-wrap: wrap; gap: 14px; margin-bottom: 55px; padding: 21px; }
  .premium-section { padding: 24px 21px; }
  .closing img { width: 50px; height: 50px; padding: 7px; }
  .closing div { flex: 1 1 200px; }
  .closing h2 { font-size: 20px; }
  .button-secondary { width: 100%; margin: 5px 0 0; }
  .site-footer { flex-direction: column; gap: 5px; }
}
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; } }