/* ============================================================
   StudyForge — intro / landing screen (logged-out visitors)
   All rules scoped under .sf-intro. No globals.
   ============================================================ */

.sf-intro {
  /* local theme tokens */
  --si-bg: #08080c;
  --si-panel: rgba(255, 255, 255, 0.03);
  --si-line: rgba(255, 255, 255, 0.08);
  --si-text: #e8e8f0;
  --si-dim: #9a9ab0;
  --si-purple: #7c6cff;
  --si-green: #57c99b;
  --si-heading: 'Space Grotesk', sans-serif;
  --si-body: 'Geist', system-ui, sans-serif;

  position: relative;
  background: var(--si-bg);
  color: var(--si-text);
  font-family: var(--si-body);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.sf-intro *,
.sf-intro *::before,
.sf-intro *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* faint ambient glow behind the hero — pure decoration */
.sf-intro .si-glow {
  position: absolute;
  top: -220px;
  left: 50%;
  transform: translateX(-50%);
  width: 900px;
  height: 560px;
  background:
    radial-gradient(closest-side, rgba(124, 108, 255, 0.16), transparent 70%);
  pointer-events: none;
  z-index: 0;
}
.sf-intro .si-glow-2 {
  top: 260px;
  left: auto;
  right: -160px;
  transform: none;
  width: 620px;
  height: 480px;
  background: radial-gradient(closest-side, rgba(87, 201, 155, 0.12), transparent 70%);
}

/* faint grid texture — adds depth without noise */
.sf-intro .si-grid-bg {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.028) 1px, transparent 1px);
  background-size: 46px 46px;
  -webkit-mask-image: radial-gradient(120% 80% at 50% 0%, #000 30%, transparent 78%);
  mask-image: radial-gradient(120% 80% at 50% 0%, #000 30%, transparent 78%);
}

.sf-intro .si-wordmark-mark {
  display: inline-flex;
  vertical-align: -3px;
  margin-right: 7px;
  color: var(--si-purple);
}
.sf-intro .si-wordmark-mark svg { width: 17px; height: 17px; }

.sf-intro .si-wrap {
  position: relative;
  z-index: 1;
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- top bar ---------- */

.sf-intro .si-topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 22px 0;
}

.sf-intro .si-wordmark {
  font-family: var(--si-heading);
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.02em;
  color: var(--si-text);
  white-space: nowrap;
}

.sf-intro .si-wordmark .si-spark {
  color: var(--si-purple);
}

.sf-intro .si-nav {
  display: flex;
  gap: 26px;
}

.sf-intro .si-nav-link {
  background: none;
  border: 0;
  cursor: pointer;
  font-family: var(--si-body);
  font-size: 0.88rem;
  color: var(--si-dim);
  padding: 4px 2px;
  transition: color 0.18s ease;
}

.sf-intro .si-nav-link:hover {
  color: var(--si-text);
}

.sf-intro .si-topbar-actions {
  display: flex;
  align-items: center;
  gap: 18px;
}

.sf-intro .si-signin-link {
  background: none;
  border: 0;
  cursor: pointer;
  font-family: var(--si-body);
  font-size: 0.88rem;
  color: var(--si-dim);
  padding: 4px 2px;
  transition: color 0.18s ease;
  white-space: nowrap;
}

.sf-intro .si-signin-link:hover {
  color: var(--si-text);
}

/* ---------- buttons ---------- */

.sf-intro .si-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: 0;
  border-radius: 10px;
  cursor: pointer;
  font-family: var(--si-body);
  font-weight: 600;
  font-size: 0.92rem;
  letter-spacing: 0.01em;
  padding: 12px 26px;
  min-width: auto;
  white-space: nowrap;
  transition: transform 0.18s ease, box-shadow 0.18s ease,
    background-color 0.18s ease, border-color 0.18s ease;
}

.sf-intro .si-btn-primary {
  background: var(--si-purple);
  color: #fff;
  box-shadow: 0 4px 24px rgba(124, 108, 255, 0.28);
}

.sf-intro .si-btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(124, 108, 255, 0.4);
}

.sf-intro .si-btn-primary:active {
  transform: translateY(0);
}

.sf-intro .si-btn-ghost {
  background: transparent;
  color: var(--si-text);
  border: 1px solid var(--si-line);
}

.sf-intro .si-btn-ghost:hover {
  border-color: rgba(255, 255, 255, 0.22);
  background: var(--si-panel);
}

.sf-intro .si-btn-small {
  padding: 9px 18px;
  font-size: 0.85rem;
}

/* ---------- hero ---------- */

.sf-intro .si-hero {
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  align-items: center;
  gap: 52px;
  padding: 60px 0 56px;
}

.sf-intro .si-hero-copy { text-align: left; }

.sf-intro .si-badge {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 0.78rem;
  letter-spacing: 0.04em;
  color: var(--si-dim);
  border: 1px solid var(--si-line);
  border-radius: 999px;
  padding: 7px 16px;
  background: var(--si-panel);
  box-shadow: 0 0 24px rgba(124, 108, 255, 0.1);
}

.sf-intro .si-badge .si-badge-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--si-green);
  box-shadow: 0 0 8px var(--si-green);
}

.sf-intro .si-headline {
  font-family: var(--si-heading);
  font-weight: 700;
  font-size: clamp(2.1rem, 5.2vw, 3.5rem);
  line-height: 1.07;
  letter-spacing: -0.03em;
  margin: 22px 0 0;
  max-width: 620px;
}

.sf-intro .si-headline .si-gradient {
  background: linear-gradient(100deg, var(--si-purple), var(--si-green));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

.sf-intro .si-subhead {
  color: var(--si-dim);
  font-size: clamp(0.95rem, 2.4vw, 1.06rem);
  max-width: 540px;
  margin: 20px 0 0;
}

.sf-intro .si-subhead strong {
  color: var(--si-text);
  font-weight: 600;
}

.sf-intro .si-hero-ctas {
  display: flex;
  justify-content: flex-start;
  gap: 14px;
  flex-wrap: wrap;
  margin-top: 32px;
}

.sf-intro .si-hero-note {
  margin-top: 16px;
  font-size: 0.78rem;
  color: var(--si-dim);
  opacity: 0.8;
}

/* ---------- hero product mockup ---------- */

.sf-intro .si-hero-visual {
  position: relative;
  justify-self: center;
  width: 100%;
  max-width: 380px;
}

.sf-intro .si-mock {
  position: relative;
  background: linear-gradient(180deg, rgba(22, 22, 34, 0.92), rgba(14, 14, 22, 0.92));
  border: 1px solid var(--si-line);
  border-radius: 18px;
  padding: 18px;
  box-shadow: 0 30px 80px rgba(0, 0, 0, 0.5), 0 0 60px rgba(124, 108, 255, 0.12);
  transform: rotate(1.4deg);
}

.sf-intro .si-mock-bar { display: flex; gap: 6px; margin-bottom: 16px; }
.sf-intro .si-mock-bar span { width: 9px; height: 9px; border-radius: 50%; background: rgba(255, 255, 255, 0.14); }
.sf-intro .si-mock-bar span:first-child { background: rgba(124, 108, 255, 0.7); }

.sf-intro .si-mock-head { display: flex; align-items: center; justify-content: space-between; margin-bottom: 14px; }
.sf-intro .si-mock-chip { font-size: 0.72rem; font-weight: 600; color: var(--si-dim); border: 1px solid var(--si-line); border-radius: 999px; padding: 4px 10px; }
.sf-intro .si-mock-rank { font-family: var(--si-heading); font-size: 0.74rem; font-weight: 700; color: #ffd24a; }

.sf-intro .si-mock-q { font-family: var(--si-heading); font-weight: 600; font-size: 1.02rem; line-height: 1.35; letter-spacing: -0.01em; margin-bottom: 14px; }

.sf-intro .si-mock-opts { display: flex; flex-direction: column; gap: 8px; }
.sf-intro .si-mock-opt {
  position: relative;
  font-size: 0.86rem;
  color: var(--si-text);
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--si-line);
  border-radius: 10px;
  padding: 11px 14px;
}
.sf-intro .si-mock-opt.is-correct {
  border-color: rgba(87, 201, 155, 0.6);
  background: rgba(87, 201, 155, 0.12);
  color: #cdeede;
  font-weight: 600;
}
.sf-intro .si-mock-tick {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--si-green);
  font-weight: 700;
}

.sf-intro .si-mock-foot { display: flex; align-items: center; gap: 12px; margin-top: 16px; }
.sf-intro .si-mock-prog { flex: 1; height: 7px; border-radius: 999px; background: rgba(255, 255, 255, 0.08); overflow: hidden; }
.sf-intro .si-mock-prog i { display: block; height: 100%; border-radius: 999px; background: linear-gradient(90deg, var(--si-purple), var(--si-green)); }
.sf-intro .si-mock-score { font-family: var(--si-heading); font-weight: 700; font-size: 0.82rem; color: var(--si-text); }

.sf-intro .si-mock-badge {
  position: absolute;
  font-family: var(--si-heading);
  font-weight: 700;
  font-size: 0.78rem;
  padding: 8px 13px;
  border-radius: 12px;
  border: 1px solid var(--si-line);
  background: rgba(16, 16, 26, 0.9);
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.45);
  animation: sfFloat 4s ease-in-out infinite;
}
.sf-intro .si-mock-badge-a { top: -18px; right: -14px; color: var(--si-green); }
.sf-intro .si-mock-badge-b { bottom: -16px; left: -18px; color: #ffd24a; animation-delay: 1.6s; }

@keyframes sfFloat { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-7px); } }

/* ---------- stats strip ---------- */

.sf-intro .si-stats {
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--si-line);
  border: 1px solid var(--si-line);
  border-radius: 14px;
  overflow: hidden;
  margin: 40px 0 0;
}

.sf-intro .si-stat {
  background: var(--si-bg);
  padding: 26px 12px;
  text-align: center;
}

.sf-intro .si-stat-num {
  display: block;
  font-family: var(--si-heading);
  font-weight: 700;
  font-size: clamp(1.4rem, 3.4vw, 2rem);
  letter-spacing: -0.02em;
  color: var(--si-text);
}

.sf-intro .si-stat:nth-child(even) .si-stat-num {
  color: var(--si-green);
}

.sf-intro .si-stat:nth-child(odd) .si-stat-num {
  color: var(--si-purple);
}

.sf-intro .si-stat-label {
  display: block;
  margin-top: 6px;
  font-size: 0.76rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--si-dim);
}

/* ---------- sections ---------- */

.sf-intro .si-section {
  padding: 88px 0 0;
}

.sf-intro .si-kicker {
  display: block;
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--si-purple);
  text-align: center;
}

.sf-intro .si-section-title {
  font-family: var(--si-heading);
  font-weight: 700;
  font-size: clamp(1.5rem, 4vw, 2.2rem);
  letter-spacing: -0.02em;
  line-height: 1.15;
  text-align: center;
  margin-top: 12px;
}

.sf-intro .si-section-sub {
  color: var(--si-dim);
  text-align: center;
  max-width: 540px;
  margin: 14px auto 0;
  font-size: 0.95rem;
}

/* ---------- feature cards ---------- */

.sf-intro .si-features-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 18px;
  margin-top: 44px;
}

.sf-intro .si-card {
  background: var(--si-panel);
  border: 1px solid var(--si-line);
  border-radius: 14px;
  padding: 28px 26px;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.sf-intro .si-card:hover {
  transform: translateY(-3px);
  border-color: rgba(124, 108, 255, 0.35);
}

.sf-intro .si-card-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 12px;
  border: 1px solid var(--si-line);
  background: rgba(124, 108, 255, 0.1);
  color: var(--si-purple);
}
.sf-intro .si-card-icon svg { width: 21px; height: 21px; }

.sf-intro .si-card:nth-child(even) .si-card-icon {
  background: rgba(87, 201, 155, 0.08);
  color: var(--si-green);
}

.sf-intro .si-card-title {
  font-family: var(--si-heading);
  font-weight: 600;
  font-size: 1.05rem;
  letter-spacing: -0.02em;
  margin-top: 16px;
}

.sf-intro .si-card-body {
  color: var(--si-dim);
  font-size: 0.9rem;
  margin-top: 8px;
}

/* ---------- how it works ---------- */

.sf-intro .si-steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
  margin-top: 44px;
}

.sf-intro .si-step {
  position: relative;
  background: var(--si-panel);
  border: 1px solid var(--si-line);
  border-radius: 14px;
  padding: 30px 24px 26px;
}

.sf-intro .si-step-num {
  font-family: var(--si-heading);
  font-weight: 700;
  font-size: 0.82rem;
  letter-spacing: 0.06em;
  color: var(--si-green);
}

.sf-intro .si-step-title {
  font-family: var(--si-heading);
  font-weight: 600;
  font-size: 1.02rem;
  letter-spacing: -0.02em;
  margin-top: 10px;
}

.sf-intro .si-step-body {
  color: var(--si-dim);
  font-size: 0.88rem;
  margin-top: 8px;
}

/* ---------- subjects note ---------- */

.sf-intro .si-subjects-list {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px;
  margin: 36px auto 0;
  max-width: 760px;
}

.sf-intro .si-subject-chip {
  font-size: 0.84rem;
  color: var(--si-text);
  border: 1px solid var(--si-line);
  background: var(--si-panel);
  border-radius: 999px;
  padding: 7px 16px;
  white-space: nowrap;
}

.sf-intro .si-subjects-note {
  text-align: center;
  color: var(--si-dim);
  font-size: 0.84rem;
  margin-top: 20px;
}

/* ---------- closing CTA band ---------- */

.sf-intro .si-cta-band {
  margin-top: 96px;
  border: 1px solid var(--si-line);
  border-radius: 18px;
  background:
    radial-gradient(80% 120% at 50% 0%, rgba(124, 108, 255, 0.12), transparent 60%),
    var(--si-panel);
  text-align: center;
  padding: 64px 28px;
}

.sf-intro .si-cta-band .si-section-title {
  margin-top: 0;
}

.sf-intro .si-cta-band .si-btn {
  margin-top: 30px;
}

/* ---------- footer ---------- */

.sf-intro .si-footer {
  text-align: center;
  color: var(--si-dim);
  font-size: 0.8rem;
  padding: 56px 0 40px;
}

/* ---------- entrance motion ---------- */

@keyframes sfIntroRise {
  from {
    opacity: 0;
    transform: translateY(14px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.sf-intro .si-rise {
  animation: sfIntroRise 0.7s cubic-bezier(0.22, 1, 0.36, 1) both;
}

.sf-intro .si-rise-1 { animation-delay: 0.05s; }
.sf-intro .si-rise-2 { animation-delay: 0.14s; }
.sf-intro .si-rise-3 { animation-delay: 0.23s; }
.sf-intro .si-rise-4 { animation-delay: 0.32s; }
.sf-intro .si-rise-5 { animation-delay: 0.41s; }

@media (prefers-reduced-motion: reduce) {
  .sf-intro .si-rise {
    animation: none;
  }
  .sf-intro .si-btn,
  .sf-intro .si-card {
    transition: none;
  }
}

/* ---------- responsive ---------- */

@media (max-width: 860px) {
  .sf-intro .si-nav {
    display: none;
  }

  .sf-intro .si-hero {
    grid-template-columns: 1fr;
    gap: 40px;
    padding: 40px 0 48px;
    text-align: center;
  }
  .sf-intro .si-hero-copy { text-align: center; order: 1; }
  .sf-intro .si-hero-visual { order: 2; grid-row: 2; margin: 6px auto 0; }
  .sf-intro .si-headline,
  .sf-intro .si-subhead { margin-left: auto; margin-right: auto; }
  .sf-intro .si-hero-ctas { justify-content: center; }
  .sf-intro .si-stats { order: 3; }

  .sf-intro .si-features-grid {
    grid-template-columns: 1fr;
  }

  .sf-intro .si-steps {
    grid-template-columns: 1fr;
  }

  .sf-intro .si-stats {
    grid-template-columns: repeat(2, 1fr);
  }

  .sf-intro .si-section {
    padding-top: 68px;
  }
}

@media (max-width: 440px) {
  .sf-intro .si-wrap {
    padding: 0 16px;
  }

  .sf-intro .si-hero {
    padding: 52px 0 44px;
  }

  .sf-intro .si-hero-ctas .si-btn {
    width: 100%;
  }

  .sf-intro .si-signin-link {
    display: none;
  }

  .sf-intro .si-cta-band {
    padding: 44px 18px;
  }
}

/* ============================================================
   Host integration — let the landing fill the viewport instead of
   the narrow, centered auth-mode column the app normally uses for the
   sign-in box. Toggled by body.intro-mode (set in js/account.js when
   the intro is shown, cleared on the next render). These deliberately
   target the app frame around .sf-intro, so they are not scoped to it.
   ============================================================ */
body.intro-mode.auth-mode { display: block !important; }
body.intro-mode .app,
body.intro-mode.auth-mode .app {
  max-width: none !important;
  width: 100% !important;
  padding: 0 !important;
  margin: 0 !important;
  display: block !important;
}
body.intro-mode::before,
body.intro-mode::after { display: none !important; }