/* =========================================================================
   FluentFable — "Slate & Stone" stylesheet
   Single source of truth: every color references a :root custom property.
   Mobile-first; breakpoints at ~640 / ~960 / ~1200.
   ========================================================================= */

:root {
  /* surfaces */
  --bg-page:        #fbf9f8;  /* warm paper — the main background */
  --surface:        #ffffff;  /* cards */
  --surface-card:   #fefdfc;
  --surface-muted:  #f0eded;  /* tinted containers, alt sections */
  --surface-assist: #f4f1f1;

  /* lines */
  --border:         #e4e2e2;  /* hairline rules — use 1px, never heavy */
  --border-strong:  #c5c6cb;
  --divider:        #eceaea;

  /* ink / text */
  --text:           #1b1c1c;  /* primary body ink */
  --text-secondary: #44474b;
  --text-muted:     #5c5e63;
  --text-tertiary:  #75777b;
  --text-subtle:    #9a9c9f;

  /* the single accent — slate */
  --ink-slate:      #202631;
  --ink-pressed:    #0e1014;
  --accent-soft:    rgba(32, 38, 49, 0.10);

  /* book-cover gradient slate */
  --cover-slate:    #353c47;
  --cover-mid:      #75777b;
  --glyph-cream:    #faf8f5;

  /* status */
  --danger:         #c0362c;

  /* radii */
  --radius-sm: 4px;
  --radius-md: 6px;
  --radius-lg: 10px;
  --radius-xl: 16px;
  --radius-pill: 999px;

  /* the only shadows permitted */
  --shadow-cover: 0 14px 28px rgba(27, 28, 28, 0.22);
  --shadow-soft:  0 10px 24px rgba(27, 28, 28, 0.08);

  /* type families */
  --font-display: 'Fraunces', Georgia, 'Times New Roman', serif;
  --font-ui:      'Inter', system-ui, -apple-system, sans-serif;
  --font-kr:      'Noto Serif KR', 'Fraunces', serif;

  /* layout */
  --maxw: 1120px;
  --gutter: 24px;
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---------- reset / base ---------- */
*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 0;
  background: var(--bg-page);
  color: var(--text);
  font-family: var(--font-ui);
  font-size: 17px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img, svg, video { max-width: 100%; height: auto; display: block; }

a { color: var(--ink-slate); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3 { font-family: var(--font-display); font-weight: 500; line-height: 1.15; letter-spacing: -0.01em; margin: 0; }

p { margin: 0; }

:focus-visible {
  outline: 2px solid var(--ink-slate);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ---------- layout helpers ---------- */
.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.section { padding-block: 64px; }
.section--muted { background: var(--surface-muted); }

.eyebrow {
  font-family: var(--font-ui);
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1.6px;
  color: var(--text-tertiary);
  margin: 0 0 12px;
}

.section__head { max-width: 640px; margin-bottom: 36px; }
.section__title { font-size: 28px; }
.section__lead { color: var(--text-muted); margin-top: 12px; }

.skip-link {
  position: absolute;
  left: -999px;
  top: 8px;
  background: var(--ink-slate);
  color: var(--glyph-cream);
  padding: 10px 16px;
  border-radius: var(--radius-md);
  z-index: 100;
}
.skip-link:focus { left: 8px; }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-ui);
  font-size: 15px;
  font-weight: 600;
  padding: 14px 28px;
  border-radius: var(--radius-pill);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background-color 150ms var(--ease), color 150ms var(--ease),
              border-color 150ms var(--ease), transform 150ms var(--ease);
  text-decoration: none;
}
.btn:hover { text-decoration: none; }

.btn--primary { background: var(--ink-slate); color: var(--glyph-cream); }
.btn--primary:hover { background: var(--ink-pressed); }
.btn--primary:active { transform: translateY(1px); }

.btn--ghost {
  background: transparent;
  color: var(--ink-slate);
  border-color: var(--border-strong);
}
.btn--ghost:hover { background: var(--accent-soft); }

.btn--sm { padding: 9px 18px; font-size: 14px; }

/* App Store badge button */
.store-badge {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  background: var(--ink-slate);
  color: var(--glyph-cream);
  padding: 12px 22px;
  border-radius: var(--radius-lg);
  transition: background-color 150ms var(--ease);
}
.store-badge:hover { background: var(--ink-pressed); text-decoration: none; }
.store-badge svg { flex: none; }
.store-badge .store-badge__sub { display: block; font-size: 11px; opacity: 0.85; line-height: 1.2; }
.store-badge .store-badge__main { display: block; font-size: 18px; font-weight: 600; line-height: 1.2; }

/* ---------- header / nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in srgb, var(--bg-page) 88%, transparent);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid transparent;
  transition: border-color 150ms var(--ease);
}
.site-header.is-scrolled { border-bottom-color: var(--border); }

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand { display: inline-flex; align-items: center; gap: 10px; color: var(--text); }
.brand:hover { text-decoration: none; }
.brand__mark {
  width: 30px; height: 30px;
  border-radius: 7px;
  background: var(--ink-slate);
  color: var(--glyph-cream);
  display: grid; place-items: center;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 15px;
}
.brand__word { font-family: var(--font-display); font-size: 20px; font-weight: 500; }

.nav__links { display: none; }
.nav__toggle {
  display: inline-flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 44px; height: 44px;
  padding: 10px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  cursor: pointer;
}
.nav__toggle span {
  display: block; height: 2px; width: 100%;
  background: var(--text);
  border-radius: 2px;
  transition: transform 150ms var(--ease), opacity 150ms var(--ease);
}
.nav__toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav__toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav__toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* mobile menu panel */
.nav__menu {
  display: none;
  border-top: 1px solid var(--border);
  background: var(--bg-page);
  padding: 8px var(--gutter) 24px;
}
.nav__menu.is-open { display: block; }
.nav__menu a:not(.btn) {
  display: block;
  padding: 14px 4px;
  font-size: 17px;
  color: var(--text);
  border-bottom: 1px solid var(--divider);
}
.nav__menu .btn { margin-top: 16px; width: 100%; }

/* ---------- hero ---------- */
.hero { padding-block: 56px 40px; }
.hero__grid { display: grid; gap: 40px; align-items: center; }
.hero__title {
  font-size: clamp(40px, 9vw, 64px);
  font-weight: 500;
  letter-spacing: -0.01em;
  max-width: 14ch;
}
.hero__lead {
  font-size: clamp(17px, 2.6vw, 19px);
  color: var(--text-muted);
  margin-top: 20px;
  max-width: 46ch;
}
.hero__ctas { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 32px; }
.hero__note { margin-top: 18px; font-size: 14px; color: var(--text-subtle); }

.hero__visual { display: flex; justify-content: center; }
.phone {
  position: relative;
  width: min(300px, 78vw);
  border-radius: 34px;
  padding: 10px;
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-cover);
}
.phone img { border-radius: 26px; }
.phone::after {
  /* speaker notch hint */
  content: "";
  position: absolute;
  top: 20px; left: 50%; transform: translateX(-50%);
  width: 78px; height: 5px; border-radius: 3px;
  background: var(--divider);
}

/* ---------- trust strip ---------- */
.trust {
  text-align: center;
  padding-block: 28px;
  background: var(--surface-muted);
  border-block: 1px solid var(--border);
}
.trust p {
  font-family: var(--font-display);
  font-size: clamp(18px, 3vw, 22px);
  color: var(--text-secondary);
  margin: 0;
}

/* ---------- features ---------- */
.feature-grid { display: grid; gap: 16px; }
.feature-card {
  background: var(--bg-page);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
}
.feature-card__icon {
  width: 40px; height: 40px;
  display: grid; place-items: center;
  color: var(--ink-slate);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  margin-bottom: 18px;
}
.feature-card__icon svg { width: 22px; height: 22px; }
.feature-card h3 { font-size: 20px; margin-bottom: 8px; }
.feature-card p { color: var(--text-muted); font-size: 15px; line-height: 1.65; }

/* ---------- how it works ---------- */
.steps { display: grid; gap: 28px; counter-reset: step; }
.step { position: relative; }
.step__num {
  font-family: var(--font-display);
  font-size: 44px;
  font-weight: 500;
  color: var(--ink-slate);
  line-height: 1;
}
.step h3 { font-size: 19px; margin: 14px 0 6px; }
.step p { color: var(--text-muted); font-size: 15px; }
.step__bar {
  margin-top: 16px;
  height: 4px;
  border-radius: 2px;
  background: var(--divider);
  overflow: hidden;
}
.step__bar i { display: block; height: 100%; background: var(--ink-slate); border-radius: 2px; }

/* ---------- screenshots ---------- */
.shots-grid {
  display: grid;
  gap: 18px;
  grid-template-columns: repeat(2, 1fr);
}
.shot {
  margin: 0;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 10px;
  cursor: zoom-in;
  transition: transform 150ms var(--ease);
}
.shot:hover { transform: translateY(-2px); }
.shot img { border-radius: var(--radius-md); width: 100%; }
.shot figcaption {
  text-align: center;
  font-size: 13px;
  color: var(--text-tertiary);
  padding: 10px 4px 4px;
}

.shot--feature { box-shadow: var(--shadow-cover); }

.video-frame {
  margin-top: 28px;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--ink-slate);
}
.video-frame img, .video-frame video { width: 100%; display: block; }

/* ---------- lightbox ---------- */
.lightbox {
  position: fixed; inset: 0;
  display: none;
  place-items: center;
  background: rgba(14, 16, 20, 0.82);
  z-index: 200;
  padding: 24px;
}
.lightbox.is-open { display: grid; }
.lightbox img { max-height: 88vh; width: auto; border-radius: var(--radius-lg); }
.lightbox__close {
  position: absolute; top: 18px; right: 18px;
  width: 44px; height: 44px;
  border-radius: var(--radius-pill);
  border: 1px solid rgba(250,248,245,0.4);
  background: transparent;
  color: var(--glyph-cream);
  font-size: 22px;
  cursor: pointer;
}

/* ---------- download band ---------- */
.download { text-align: center; }
.download__title { font-size: clamp(28px, 5vw, 40px); max-width: 16ch; margin-inline: auto; }
.download__badges { display: flex; flex-wrap: wrap; gap: 14px; justify-content: center; margin-top: 28px; }
.download__note { margin-top: 16px; color: var(--text-tertiary); font-size: 14px; }

/* ---------- FAQ ---------- */
.faq { max-width: 760px; }
.faq details {
  border-bottom: 1px solid var(--border);
  padding: 4px 0;
}
.faq summary {
  list-style: none;
  cursor: pointer;
  padding: 18px 36px 18px 0;
  position: relative;
  font-family: var(--font-display);
  font-size: 19px;
  color: var(--text);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: "+";
  position: absolute;
  right: 4px; top: 50%; transform: translateY(-50%);
  font-family: var(--font-ui);
  font-size: 22px;
  color: var(--text-tertiary);
  transition: transform 150ms var(--ease);
}
.faq details[open] summary::after { content: "\2013"; }
.faq p { color: var(--text-muted); font-size: 16px; padding: 0 36px 20px 0; }
.faq .placeholder-note { font-size: 13px; }

/* ---------- footer ---------- */
.site-footer {
  background: var(--surface-muted);
  border-top: 1px solid var(--border);
  padding-block: 48px;
}
.footer__grid {
  display: grid;
  gap: 32px;
}
.footer__tagline { color: var(--text-muted); margin-top: 12px; max-width: 36ch; font-size: 15px; }
.footer__links { display: flex; flex-wrap: wrap; gap: 20px 28px; }
.footer__links a { color: var(--text-secondary); font-size: 15px; }
.footer__copy { margin-top: 28px; color: var(--text-subtle); font-size: 13px; }

/* ---------- legal pages ---------- */
.legal { max-width: 720px; padding-block: 56px; }
.legal h1 { font-size: clamp(32px, 6vw, 44px); }
.legal h2 { font-size: 24px; margin-top: 44px; scroll-margin-top: 80px; }
.legal h3 { font-family: var(--font-display); font-weight: 500; font-size: 18px; margin-top: 28px; }
.legal .updated { color: var(--text-tertiary); font-size: 14px; margin-top: 8px; }
.legal p, .legal li { color: var(--text-secondary); margin-top: 16px; }
.legal ul { padding-left: 22px; }
.legal li { margin-top: 8px; }
.legal a { text-decoration: underline; }
.legal .back { display: inline-block; margin-top: 48px; font-size: 15px; }

/* legal: intro/summary callout + table of contents */
.legal .legal-lead { color: var(--text-muted); }
.legal .toc { background: var(--surface-assist); border: 1px solid var(--border); border-radius: var(--radius-lg); padding: 8px 22px; }
.legal .toc ol { margin: 0; padding-left: 20px; }
.legal .toc li { margin-top: 6px; color: var(--text-secondary); }

/* legal: data-category table */
.legal .table-wrap { overflow-x: auto; margin-top: 20px; }
.legal table { width: 100%; border-collapse: collapse; font-size: 14px; min-width: 520px; }
.legal th, .legal td { border: 1px solid var(--border); padding: 10px 12px; text-align: left; vertical-align: top; color: var(--text-secondary); }
.legal th { background: var(--surface-muted); font-family: var(--font-ui); font-weight: 600; color: var(--text); }
.legal td.yesno { text-align: center; white-space: nowrap; font-weight: 600; }

.placeholder-note {
  display: block;
  background: var(--surface-assist);
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius-md);
  color: var(--text-muted);
  padding: 16px 18px;
  margin-top: 24px;
  font-size: 15px;
}

/* ---------- scroll reveal ---------- */
.reveal { opacity: 0; transform: translateY(16px); transition: opacity 500ms var(--ease), transform 500ms var(--ease); }
.reveal.is-visible { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
}

/* =========================================================================
   Breakpoints
   ========================================================================= */
@media (min-width: 640px) {
  .feature-grid { grid-template-columns: repeat(2, 1fr); }
  .steps { grid-template-columns: repeat(3, 1fr); }
  .shots-grid { grid-template-columns: repeat(4, 1fr); }
  .footer__grid { grid-template-columns: 1.4fr 1fr; align-items: start; }
}

@media (min-width: 960px) {
  .section { padding-block: 88px; }
  .nav__toggle { display: none; }
  .nav__links {
    display: flex;
    align-items: center;
    gap: 28px;
  }
  .nav__links a { color: var(--text-secondary); font-size: 15px; }
  .nav__links a:not(.btn):hover { color: var(--text); }
  .nav__menu { display: none !important; }

  .hero { padding-block: 80px 56px; }
  .hero__grid { grid-template-columns: 1.05fr 0.95fr; gap: 56px; }
  .feature-grid { grid-template-columns: repeat(4, 1fr); }
  .section__title { font-size: 34px; }
}