/* ==========================================================================
   AI Tutor Bot — Landing Page Styles
   Production build · Light mode only · Mobile-first
   ========================================================================== */

/* -------------------------------------------------------------------------
   0. Custom Font
   ------------------------------------------------------------------------- */
@font-face {
  font-family: "Inter Variable";
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url("../assets/fonts/Inter-Variable.woff2") format("woff2");
}

/* -------------------------------------------------------------------------
   1. Custom Properties (Design Tokens)
   ------------------------------------------------------------------------- */
:root {
  /* Palette */
  --color-primary: #0EA5E9;
  --color-primary-dark: #0284C7;
  --color-primary-light: #38BDF8;
  --color-accent: #F59E0B;
  --color-accent-dark: #D97706;
  --color-bg: #F8FAFC;
  --color-card: #FFFFFF;
  --color-text: #1E293B;
  --color-text-secondary: #475569;
  --color-text-tertiary: #94A3B8;
  --color-success: #10B981;
  --color-telegram: #229ED9;
  --color-border: #E2E8F0;
  --color-border-light: #F1F5F9;

  /* Typography */
  --font-family: "Inter Variable", "Inter", system-ui, -apple-system, sans-serif;
  --font-size-body: 18px;
  --line-height-body: 1.65;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  --font-weight-extrabold: 800;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;

  /* Layout */
  --container-max: 1200px;
  --container-padding: 1.25rem;
  --navbar-height: 72px;

  /* Radii */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.12);
  --shadow-card: 0 2px 8px rgba(0, 0, 0, 0.04), 0 4px 24px rgba(0, 0, 0, 0.06);
  --shadow-glow: 0 0 40px rgba(14, 165, 233, 0.15);

  /* Glass */
  --glass-bg: rgba(255, 255, 255, 0.7);
  --glass-border: rgba(255, 255, 255, 0.5);
  --glass-blur: 12px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
  --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* -------------------------------------------------------------------------
   2. Reset & Base
   ------------------------------------------------------------------------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 100%;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-padding-top: var(--navbar-height);
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-body);
  line-height: var(--line-height-body);
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

a {
  color: inherit;
  text-decoration: none;
}

ul,
ol {
  list-style: none;
}

button {
  font: inherit;
  color: inherit;
  background: none;
  border: none;
  cursor: pointer;
}

input,
textarea {
  font: inherit;
}

h1, h2, h3, h4, h5, h6 {
  line-height: 1.2;
  text-wrap: balance;
}

p {
  text-wrap: pretty;
}

/* -------------------------------------------------------------------------
   3. Utility — Container & Section Titles
   ------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-padding);
}

.section-title {
  font-size: clamp(1.5rem, 3vw, 2.5rem);
  font-weight: var(--font-weight-bold);
  color: var(--color-text);
  text-align: center;
  margin-bottom: var(--space-md);
}

.section-subtitle {
  font-size: clamp(1rem, 1.5vw, 1.15rem);
  color: var(--color-text-secondary);
  text-align: center;
  max-width: 640px;
  margin-inline: auto;
  margin-bottom: var(--space-3xl);
}

/* -------------------------------------------------------------------------
   4. Buttons
   ------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 0.75rem 1.75rem;
  font-size: 1rem;
  font-weight: var(--font-weight-semibold);
  line-height: 1.4;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition:
    background-color var(--transition-base),
    box-shadow var(--transition-base),
    transform var(--transition-fast);
  white-space: nowrap;
  text-decoration: none;
  -webkit-user-select: none;
  user-select: none;
}

.btn:active {
  transform: scale(0.97);
}

.btn--primary {
  background-color: var(--color-primary);
  color: #fff;
  box-shadow: 0 2px 8px rgba(14, 165, 233, 0.3);
}

.btn--primary:hover {
  background-color: var(--color-primary-dark);
  box-shadow: 0 4px 16px rgba(14, 165, 233, 0.4);
}

.btn--accent {
  background-color: var(--color-accent);
  color: #fff;
  box-shadow: 0 2px 8px rgba(245, 158, 11, 0.3);
}

.btn--accent:hover {
  background-color: var(--color-accent-dark);
  box-shadow: 0 4px 16px rgba(245, 158, 11, 0.4);
}

.btn--sm {
  padding: 0.5rem 1.25rem;
  font-size: 0.9rem;
  border-radius: var(--radius-sm);
}

.btn--large {
  padding: 1rem 2.25rem;
  font-size: 1.1rem;
  border-radius: var(--radius-md);
}

.btn--block {
  display: flex;
  width: 100%;
}

/* -------------------------------------------------------------------------
   5. Navbar
   ------------------------------------------------------------------------- */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(248, 250, 252, 0.85);
  backdrop-filter: blur(var(--glass-blur));
  -webkit-backdrop-filter: blur(var(--glass-blur));
  transition:
    padding var(--transition-base),
    box-shadow var(--transition-base),
    background-color var(--transition-base);
}

.navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--container-max);
  margin-inline: auto;
  padding: 1rem var(--container-padding);
  transition: padding var(--transition-base);
}

.navbar--scrolled {
  background: rgba(248, 250, 252, 0.95);
  box-shadow: var(--shadow-md);
}

.navbar--scrolled .navbar__inner {
  padding-top: 0.6rem;
  padding-bottom: 0.6rem;
}

.navbar__logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 1.25rem;
  font-weight: var(--font-weight-bold);
  color: var(--color-text);
  z-index: 10;
}

.navbar__logo-icon {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  object-fit: contain;
}

.navbar__nav {
  align-items: center;
  gap: var(--space-xl);
}

.navbar__link {
  font-size: 0.95rem;
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  transition: color var(--transition-fast);
  position: relative;
}

.navbar__link::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-primary);
  border-radius: 1px;
  transition: width var(--transition-base);
}

.navbar__link:hover {
  color: var(--color-primary);
}

.navbar__link:hover::after {
  width: 100%;
}

.navbar__cta {
  display: none;
}

/* Burger */
.navbar__burger {
  display: flex;
  flex-direction: column;
  gap: 5px;
  width: 28px;
  padding: 4px 0;
  cursor: pointer;
  z-index: 10;
}

.navbar__burger span {
  display: block;
  height: 2px;
  width: 100%;
  background-color: var(--color-text);
  border-radius: 2px;
  transition: transform var(--transition-base), opacity var(--transition-fast);
}

.navbar--open .navbar__burger span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.navbar--open .navbar__burger span:nth-child(2) {
  opacity: 0;
}

.navbar--open .navbar__burger span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Mobile nav — floating dropdown panel */
.navbar__nav {
  display: flex;
  flex-direction: column;
  position: absolute;
  top: calc(100% + 8px);
  left: 12px;
  right: 12px;
  background: #fff;
  border: 1px solid rgba(226, 232, 240, 0.8);
  border-radius: 16px;
  box-shadow:
    0 12px 40px rgba(0, 0, 0, 0.1),
    0 4px 12px rgba(0, 0, 0, 0.05);
  padding: 8px;
  gap: 0;
  align-items: stretch;
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transform: translateY(-12px) scale(0.97);
  transform-origin: top center;
  transition:
    max-height 0.45s cubic-bezier(0.32, 0.72, 0, 1),
    opacity 0.35s cubic-bezier(0.32, 0.72, 0, 1),
    transform 0.35s cubic-bezier(0.32, 0.72, 0, 1);
  pointer-events: none;
}

.navbar--open .navbar__nav {
  max-height: 420px;
  opacity: 1;
  transform: translateY(0) scale(1);
  pointer-events: auto;
}

.navbar__nav .navbar__link {
  display: block;
  padding: 0.9rem 1.2rem;
  font-size: 1rem;
  font-weight: var(--font-weight-medium);
  color: var(--color-text);
  border-radius: 10px;
  transition:
    background 0.2s ease,
    color 0.2s ease,
    transform 0.4s cubic-bezier(0.32, 0.72, 0, 1),
    opacity 0.4s cubic-bezier(0.32, 0.72, 0, 1);
  transform: translateY(-8px);
  opacity: 0;
}

.navbar--open .navbar__nav .navbar__link {
  transform: translateY(0);
  opacity: 1;
}

.navbar--open .navbar__nav .navbar__link:nth-child(1) { transition-delay: 0.04s; }
.navbar--open .navbar__nav .navbar__link:nth-child(2) { transition-delay: 0.08s; }
.navbar--open .navbar__nav .navbar__link:nth-child(3) { transition-delay: 0.12s; }
.navbar--open .navbar__nav .navbar__link:nth-child(4) { transition-delay: 0.16s; }
.navbar--open .navbar__nav .navbar__link:nth-child(5) { transition-delay: 0.20s; }

.navbar__nav .navbar__link:active,
.navbar__nav .navbar__link:hover {
  background: rgba(14, 165, 233, 0.06);
  color: var(--color-primary);
}

.navbar__nav .navbar__link::after {
  display: none;
}

/* Mobile menu CTA button inside dropdown */
.navbar__mobile-cta {
  display: block;
  margin: 4px 8px 8px;
  text-align: center;
  padding: 0.85rem 1.5rem;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #fff;
  font-weight: var(--font-weight-semibold);
  font-size: 0.95rem;
  border-radius: 10px;
  transition:
    background 0.2s ease,
    transform 0.4s cubic-bezier(0.32, 0.72, 0, 1),
    opacity 0.4s cubic-bezier(0.32, 0.72, 0, 1),
    box-shadow 0.2s ease;
  transform: translateY(-8px);
  opacity: 0;
  box-shadow: 0 2px 8px rgba(14, 165, 233, 0.3);
}

.navbar--open .navbar__mobile-cta {
  transform: translateY(0);
  opacity: 1;
  transition-delay: 0.24s;
}

.navbar__mobile-cta:hover {
  box-shadow: 0 4px 16px rgba(14, 165, 233, 0.4);
}

/* Overlay backdrop when menu is open */
.navbar__overlay {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.18);
  z-index: -1;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.35s cubic-bezier(0.32, 0.72, 0, 1);
}

.navbar--open .navbar__overlay {
  opacity: 1;
  pointer-events: auto;
}

/* -------------------------------------------------------------------------
   6. Hero
   ------------------------------------------------------------------------- */
.hero {
  padding-top: calc(var(--navbar-height) + 2rem);
  padding-bottom: var(--space-3xl);
  overflow: hidden;
}

.hero__inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2xl);
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-padding);
}

.hero__content {
  text-align: center;
  max-width: 600px;
}

.hero__title {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: var(--font-weight-extrabold);
  color: var(--color-text);
  margin-bottom: var(--space-lg);
  letter-spacing: -0.02em;
}

.hero__title span {
  color: var(--color-primary);
}

.hero__subtitle {
  font-size: clamp(1rem, 2vw, 1.2rem);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  line-height: 1.7;
}

.hero__cta-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  align-items: center;
  margin-bottom: var(--space-md);
}

.hero__cta-note {
  font-size: 0.85rem;
  color: var(--color-text-tertiary);
}

.hero__visual {
  flex-shrink: 0;
  display: flex;
  justify-content: center;
}

/* Trust strip */
.hero__trust {
  width: 100%;
  margin-top: var(--space-2xl);
}

.hero__trust-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-lg) var(--space-2xl);
}

.trust-item {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  font-weight: var(--font-weight-medium);
}

.trust-item svg {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
  color: var(--color-success);
}

/* -------------------------------------------------------------------------
   7. Phone Mockup
   ------------------------------------------------------------------------- */
.phone-mock {
  width: 280px;
  background: #fff;
  border-radius: 28px;
  box-shadow:
    0 0 0 2px #E2E8F0,
    var(--shadow-xl),
    var(--shadow-glow);
  overflow: hidden;
  position: relative;
}

.phone-mock::before {
  content: "";
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 100px;
  height: 24px;
  background: var(--color-bg);
  border-radius: 0 0 16px 16px;
  z-index: 2;
}

.phone-mock__header {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 2rem 1rem 0.75rem;
  background: var(--color-telegram);
  color: #fff;
}

.phone-mock__avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.25);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  flex-shrink: 0;
}

.phone-mock__name {
  font-size: 0.9rem;
  font-weight: var(--font-weight-semibold);
}

.phone-mock__status {
  font-size: 0.72rem;
  opacity: 0.8;
}

.phone-mock__chat {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  padding: var(--space-md);
  background: #E8F4F8;
  min-height: 320px;
}

/* -------------------------------------------------------------------------
   8. Chat Messages
   ------------------------------------------------------------------------- */
.chat-msg {
  max-width: 85%;
  padding: 0.6rem 0.85rem;
  border-radius: var(--radius-md);
  font-size: 0.82rem;
  line-height: 1.5;
  word-wrap: break-word;
  position: relative;
}

.chat-msg--user {
  align-self: flex-end;
  background: #DCF8C6;
  border-bottom-right-radius: 4px;
  color: var(--color-text);
}

.chat-msg--bot {
  align-self: flex-start;
  background: #fff;
  border-bottom-left-radius: 4px;
  color: var(--color-text);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.06);
}

.chat-msg--success {
  align-self: flex-start;
  background: #D1FAE5;
  border-bottom-left-radius: 4px;
  color: #065F46;
}

.chat-msg__photo-placeholder {
  width: 100%;
  aspect-ratio: 4 / 3;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, #CBD5E1, #94A3B8);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 1.5rem;
  margin-bottom: var(--space-xs);
}

/* Animated entrance */
.chat-msg--animated {
  opacity: 0;
  transform: translateY(10px);
  animation: chatMsgIn 0.4s ease forwards;
  animation-delay: var(--delay, 0s);
}

@keyframes chatMsgIn {
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* -------------------------------------------------------------------------
   9. Stats Section
   ------------------------------------------------------------------------- */
.stats {
  padding: var(--space-3xl) 0;
  background: linear-gradient(135deg, #EFF6FF 0%, #F0F9FF 50%, #ECFDF5 100%);
}

.stats__inner {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-padding);
}

.stat-card {
  text-align: center;
  padding: var(--space-xl) var(--space-lg);
  background: var(--glass-bg);
  backdrop-filter: blur(var(--glass-blur));
  -webkit-backdrop-filter: blur(var(--glass-blur));
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.stat-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.stat-card__number {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: var(--font-weight-extrabold);
  color: var(--color-primary);
  line-height: 1.1;
}

.stat-card__plus {
  font-weight: var(--font-weight-bold);
}

.stat-card__unit {
  font-size: 0.5em;
  font-weight: var(--font-weight-semibold);
}

.stat-card__label {
  margin-top: var(--space-sm);
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  font-weight: var(--font-weight-medium);
}

/* -------------------------------------------------------------------------
   10. How It Works
   ------------------------------------------------------------------------- */
.how-it-works {
  padding: var(--space-4xl) 0;
}

.steps {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-xl);
  position: relative;
}

.step {
  text-align: center;
  position: relative;
}

.step__icon {
  width: 64px;
  height: 64px;
  margin-inline: auto;
  margin-bottom: var(--space-md);
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  color: #fff;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  position: relative;
}

.step__num {
  position: absolute;
  top: -6px;
  right: -6px;
  width: 24px;
  height: 24px;
  background: var(--color-accent);
  color: #fff;
  font-size: 0.75rem;
  font-weight: var(--font-weight-bold);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
}

.step__title {
  font-size: 1.05rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
  color: var(--color-text);
}

.step__text {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
  max-width: 240px;
  margin-inline: auto;
}

/* -------------------------------------------------------------------------
   11. Modes Section
   ------------------------------------------------------------------------- */
.modes {
  padding: var(--space-4xl) 0;
  background: var(--color-bg);
}

.modes__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-xl);
  margin-bottom: var(--space-xl);
}

.modes__note {
  text-align: center;
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  font-style: italic;
}

.mode-card {
  position: relative;
  padding: var(--space-2xl);
  background: var(--glass-bg);
  backdrop-filter: blur(var(--glass-blur));
  -webkit-backdrop-filter: blur(var(--glass-blur));
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
  overflow: hidden;
}

.mode-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-primary-light));
}

.mode-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.mode-card__badge,
.mode-card__badge--alt {
  display: inline-block;
  padding: 0.3rem 0.85rem;
  font-size: 0.78rem;
  font-weight: var(--font-weight-semibold);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-md);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.mode-card__badge {
  background: rgba(14, 165, 233, 0.1);
  color: var(--color-primary-dark);
}

.mode-card__badge--alt {
  background: rgba(245, 158, 11, 0.1);
  color: var(--color-accent-dark);
}

.mode-card__title {
  font-size: 1.3rem;
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--space-md);
  color: var(--color-text);
}

.mode-card__text {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  line-height: 1.65;
  margin-bottom: var(--space-lg);
}

.mode-card__for {
  font-size: 0.85rem;
  color: var(--color-text-tertiary);
  padding-top: var(--space-md);
  border-top: 1px solid var(--color-border-light);
}

/* -------------------------------------------------------------------------
   12. Features Section
   ------------------------------------------------------------------------- */
.features {
  padding: var(--space-4xl) 0;
}

.features__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

.feature-card {
  padding: var(--space-xl);
  background: var(--color-card);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-lg);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-card);
}

.feature-card__icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: rgba(14, 165, 233, 0.1);
  color: var(--color-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  margin-bottom: var(--space-md);
}

.feature-card__title {
  font-size: 1.1rem;
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
  color: var(--color-text);
}

.feature-card__text {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

.feature-card__science {
  margin-top: var(--space-md);
  padding: var(--space-sm) var(--space-md);
  font-size: 0.78rem;
  color: var(--color-primary-dark);
  background: rgba(14, 165, 233, 0.06);
  border-left: 3px solid var(--color-primary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  line-height: 1.5;
  font-style: italic;
}

/* -------------------------------------------------------------------------
   13. Audience / Tabs Section
   ------------------------------------------------------------------------- */
.audience {
  padding: var(--space-4xl) 0;
  background: var(--color-bg);
}

.tabs__nav {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: var(--space-2xl);
}

.tabs__btn {
  padding: 0.6rem 1.4rem;
  font-size: 0.95rem;
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition:
    background-color var(--transition-fast),
    color var(--transition-fast),
    border-color var(--transition-fast),
    box-shadow var(--transition-fast);
}

.tabs__btn:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.tabs__btn--active {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
  box-shadow: 0 2px 8px rgba(14, 165, 233, 0.3);
}

.tabs__btn--active:hover {
  color: #fff;
}

.tabs__content {
  position: relative;
}

.tabs__pane {
  display: none;
  opacity: 0;
  transition: opacity var(--transition-base);
}

.tabs__pane--active {
  display: block;
  opacity: 1;
}

/* Problem grid (student tab) */
.problem-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

.problem-card {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-lg) var(--space-xl);
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: box-shadow var(--transition-base), transform var(--transition-base);
  box-shadow: var(--shadow-sm);
}

.problem-card:hover {
  box-shadow: var(--shadow-card);
  transform: translateY(-2px);
}

.problem-card__emoji {
  flex-shrink: 0;
  font-size: 1.6rem;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-bg);
  border-radius: var(--radius-md);
}

.problem-card__problem {
  flex: 1;
  font-size: 1rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  line-height: 1.4;
}

.problem-card__arrow {
  flex-shrink: 0;
  color: var(--color-primary);
  font-size: 1.4rem;
  font-weight: var(--font-weight-bold);
}

.problem-card__solution {
  flex: 1.2;
  font-size: 0.95rem;
  color: var(--color-primary-dark);
  font-weight: var(--font-weight-medium);
  line-height: 1.5;
}

/* Single-column grid for teacher tab */
.problem-grid--single {
  grid-template-columns: 1fr !important;
  max-width: 640px;
  margin-inline: auto;
}

/* Parent tab */
.parent-tab {
  max-width: 640px;
  margin-inline: auto;
}

.parent-report {
  margin-top: var(--space-2xl);
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}

.parent-report__title {
  padding: var(--space-lg) var(--space-xl);
  background: linear-gradient(135deg, #EFF6FF, #F0F9FF);
  font-size: 1.05rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  border-bottom: 1px solid var(--color-border-light);
}

.parent-report__body {
  padding: var(--space-xl);
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.parent-tab__intro {
  text-align: center;
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  font-weight: var(--font-weight-medium);
}

.parent-tab__note {
  text-align: center;
  font-size: 0.9rem;
  color: var(--color-text-tertiary);
  margin-top: var(--space-lg);
  font-style: italic;
}

.report-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

@media (min-width: 480px) {
  .report-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.report-section__label {
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  font-size: 0.88rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: var(--space-sm);
  padding-bottom: var(--space-xs);
  border-bottom: 2px solid var(--color-primary-light);
  display: inline-block;
}

.report-section ul {
  list-style: none;
  padding: 0;
}

.report-section li {
  padding: var(--space-xs) 0;
  font-size: 0.88rem;
  border-bottom: 1px solid var(--color-border-light);
}

.report-section li:last-child {
  border-bottom: none;
}

.report-footer {
  margin-top: var(--space-lg);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border);
}

.report-footer__tip {
  font-size: 0.85rem;
  color: var(--color-primary-dark);
  background: rgba(14, 165, 233, 0.06);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  line-height: 1.6;
}

/* Teacher tab */
.teacher-tab {
  max-width: 640px;
  margin-inline: auto;
}

.teacher-note {
  max-width: 640px;
  margin-inline: auto;
  margin-top: var(--space-xl);
  padding: var(--space-xl);
  background: var(--color-card);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

/* -------------------------------------------------------------------------
   14. Comparison Table
   ------------------------------------------------------------------------- */
.comparison {
  padding: var(--space-4xl) 0;
}

.comparison__wrapper {
  max-width: 800px;
  margin-inline: auto;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.comparison__col-label { width: 33%; }
.comparison__col-tutor { width: 33%; }
.comparison__col-bot   { width: 34%; }

.comparison__table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
  background: var(--color-card);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-card);
}

.comparison__table thead {
  background: var(--color-bg);
}

.comparison__table th,
.comparison__table td {
  padding: 1rem 1.5rem;
  text-align: center;
  border-bottom: 1px solid var(--color-border-light);
}

.comparison__table th {
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.comparison__table th:first-child,
.comparison__table td:first-child {
  text-align: left;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
}

.comparison__table tbody tr:last-child td {
  border-bottom: none;
}

.comparison__table tbody tr:hover {
  background: rgba(14, 165, 233, 0.02);
}

.comparison__highlight {
  background: rgba(14, 165, 233, 0.06);
  position: relative;
  font-weight: var(--font-weight-semibold);
  color: var(--color-primary-dark);
}

.comparison__highlight::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--color-primary);
}

thead .comparison__highlight {
  color: var(--color-primary-dark);
  font-weight: var(--font-weight-bold);
}

/* -------------------------------------------------------------------------
   15. Pricing Section
   ------------------------------------------------------------------------- */
.pricing {
  padding: var(--space-4xl) 0;
  background: var(--color-bg);
}

.pricing__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-xl);
  align-items: start;
}

.pricing-card {
  padding: var(--space-2xl);
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  text-align: center;
  transition: transform var(--transition-base), box-shadow var(--transition-base);
  position: relative;
}

.pricing-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.pricing-card--popular {
  border-color: var(--color-primary);
  border-width: 2px;
  box-shadow: var(--shadow-lg), var(--shadow-glow);
}

.pricing-card--popular:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-xl), var(--shadow-glow);
}

.pricing-card__badge {
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-primary);
  color: #fff;
  font-size: 0.78rem;
  font-weight: var(--font-weight-semibold);
  padding: 0.3rem 1rem;
  border-radius: var(--radius-full);
  white-space: nowrap;
}

.pricing-card__name {
  font-size: 1.1rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  margin-bottom: var(--space-md);
}

.pricing-card__price {
  font-size: clamp(2rem, 3.5vw, 2.75rem);
  font-weight: var(--font-weight-extrabold);
  color: var(--color-text);
  margin-bottom: var(--space-sm);
}

.pricing-card__price span {
  font-size: 0.45em;
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
}

.pricing-card__old-price {
  display: block;
  font-size: 0.45em;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text-tertiary);
  text-decoration: line-through;
  text-decoration-color: #EF4444;
  text-decoration-thickness: 2px;
  margin-bottom: 0.2rem;
}

.pricing-card__promo {
  font-size: 0.85rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-success);
  margin-bottom: var(--space-lg);
  padding: 0.3rem 0.8rem;
  background: rgba(16, 185, 129, 0.1);
  border-radius: var(--radius-full);
  display: inline-block;
}

.pricing-card__features {
  list-style: none;
  text-align: left;
  margin-bottom: var(--space-xl);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.pricing-card__features li {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  padding-left: 1.6rem;
  position: relative;
  line-height: 1.5;
}

.pricing-card__features li::before {
  content: "\2713";
  position: absolute;
  left: 0;
  color: var(--color-success);
  font-weight: var(--font-weight-bold);
}

/* -------------------------------------------------------------------------
   16. Security Section
   ------------------------------------------------------------------------- */
.security {
  padding: var(--space-4xl) 0;
}

.security__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-lg);
}

.security-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
  padding: var(--space-lg);
  background: var(--color-card);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-md);
  transition: box-shadow var(--transition-base);
}

.security-item:hover {
  box-shadow: var(--shadow-card);
}

.security-item svg,
.security-item img {
  width: 32px;
  height: 32px;
  flex-shrink: 0;
  color: var(--color-primary);
}

.security-item strong {
  display: block;
  font-size: 1rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  margin-bottom: var(--space-xs);
}

.security-item p {
  font-size: 0.88rem;
  color: var(--color-text-secondary);
  line-height: 1.55;
}

/* -------------------------------------------------------------------------
   17. FAQ / Accordion
   ------------------------------------------------------------------------- */
.faq {
  padding: var(--space-4xl) 0;
  background: var(--color-bg);
}

.accordion {
  max-width: 768px;
  margin-inline: auto;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.accordion__item {
  background: var(--color-card);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: box-shadow var(--transition-base), border-color var(--transition-base);
}

.accordion__item--open {
  border-color: var(--color-primary);
  box-shadow: 0 2px 12px rgba(14, 165, 233, 0.1);
}

.accordion__trigger {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: var(--space-lg) var(--space-xl);
  font-size: 1rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
  text-align: left;
  cursor: pointer;
  background: none;
  border: none;
  gap: var(--space-md);
  transition: color var(--transition-fast);
}

.accordion__trigger:hover {
  color: var(--color-primary);
}

.accordion__arrow {
  flex-shrink: 0;
  width: 20px;
  height: 20px;
  color: var(--color-text-tertiary);
  transition: transform var(--transition-base), color var(--transition-base);
}

.accordion__item--open .accordion__arrow {
  transform: rotate(180deg);
  color: var(--color-primary);
}

.accordion__content {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-slow), padding var(--transition-slow);
}

.accordion__item--open .accordion__content {
  max-height: 500px;
}

.accordion__content p,
.accordion__content div {
  padding: 0 var(--space-xl) var(--space-lg);
  font-size: 0.92rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

/* -------------------------------------------------------------------------
   Testimonials
   ------------------------------------------------------------------------- */
.testimonials {
  padding: var(--space-4xl) 0;
}

.testimonials__grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-xl);
  max-width: 900px;
  margin-inline: auto;
}

@media (min-width: 768px) {
  .testimonials__grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

.testimonial-card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-base), transform var(--transition-base);
}

.testimonial-card:hover {
  box-shadow: var(--shadow-card);
  transform: translateY(-3px);
}

.testimonial-card__header {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.testimonial-card__avatar {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: var(--font-weight-bold);
  font-size: 1.1rem;
  flex-shrink: 0;
}

.testimonial-card__name {
  font-size: 0.92rem;
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
}

.testimonial-card__date {
  font-size: 0.8rem;
  color: var(--color-text-tertiary);
  margin-top: 2px;
}

.testimonial-card__text {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

/* -------------------------------------------------------------------------
   18. Final CTA
   ------------------------------------------------------------------------- */
.final-cta {
  padding: var(--space-4xl) 0;
  background: linear-gradient(135deg, #0369A1, #0EA5E9, #38BDF8);
  color: #fff;
  text-align: center;
}

.final-cta__inner {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-padding);
}

.final-cta__title {
  font-size: clamp(1.5rem, 3vw, 2.5rem);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--space-md);
}

.final-cta__subtitle {
  font-size: clamp(1rem, 1.5vw, 1.15rem);
  opacity: 0.9;
  margin-bottom: var(--space-2xl);
  max-width: 560px;
  margin-inline: auto;
}

.final-cta .btn--accent {
  box-shadow: 0 4px 20px rgba(245, 158, 11, 0.4);
}

.final-cta .btn--accent:hover {
  box-shadow: 0 6px 28px rgba(245, 158, 11, 0.5);
  transform: translateY(-2px);
}

/* -------------------------------------------------------------------------
   19. Footer
   ------------------------------------------------------------------------- */
.footer {
  padding: var(--space-2xl) 0;
  background: #0F172A;
  color: #CBD5E1;
}

.footer__inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-lg);
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-padding);
  text-align: center;
}

.footer__brand {
  font-size: 1.15rem;
  font-weight: var(--font-weight-bold);
  color: #F1F5F9;
}

.footer__links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md) var(--space-xl);
  justify-content: center;
}

.footer__links a {
  font-size: 0.88rem;
  color: #94A3B8;
  transition: color var(--transition-fast);
}

.footer__links a:hover {
  color: var(--color-primary-light);
}

.footer__copy {
  font-size: 0.8rem;
  color: #64748B;
}

/* =========================================================================
   RESPONSIVE BREAKPOINTS
   ========================================================================= */

/* -------------------------------------------------------------------------
   480px — Small phones to larger phones
   ------------------------------------------------------------------------- */
@media (min-width: 480px) {
  :root {
    --container-padding: 1.5rem;
  }

  .hero__cta-group {
    flex-direction: row;
    justify-content: center;
  }

  .stats__inner {
    grid-template-columns: repeat(2, 1fr);
  }

  .security__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .phone-mock {
    width: 300px;
  }
}

/* -------------------------------------------------------------------------
   768px — Tablets
   ------------------------------------------------------------------------- */
@media (min-width: 768px) {
  :root {
    --container-padding: 2rem;
  }

  .navbar__nav {
    position: static;
    flex-direction: row;
    max-height: none;
    opacity: 1;
    transform: none;
    overflow: visible;
    background: none;
    backdrop-filter: none;
    -webkit-backdrop-filter: none;
    border-bottom: none;
    box-shadow: none;
    padding: 0;
    gap: var(--space-xl);
    pointer-events: auto;
    transition: none;
  }

  .navbar__nav .navbar__link {
    padding: 0;
    font-size: 0.95rem;
    border-bottom: none;
    transform: none;
    opacity: 1;
  }

  .navbar__nav .navbar__link::after {
    display: block;
  }

  .navbar__nav .navbar__link:hover {
    background: none;
  }

  .navbar__mobile-cta {
    display: none !important;
  }

  .navbar__overlay {
    display: none !important;
  }

  .navbar__cta {
    display: inline-flex;
  }

  .navbar__burger {
    display: none;
  }

  /* Hero two-column */
  .hero {
    padding-top: calc(var(--navbar-height) + 3rem);
    padding-bottom: var(--space-4xl);
  }

  .hero__inner {
    flex-direction: row;
    text-align: left;
    align-items: center;
  }

  .hero__content {
    text-align: left;
    flex: 1;
    min-width: 0;
  }

  .hero__cta-group {
    justify-content: flex-start;
  }

  .hero__visual {
    flex: 0 0 auto;
  }

  .phone-mock {
    width: 310px;
  }

  .phone-mock__chat {
    min-height: 360px;
  }

  /* Stats */
  .stats__inner {
    grid-template-columns: repeat(4, 1fr);
  }

  /* Steps: 2-column interim */
  .steps {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-2xl);
  }

  /* Modes: side by side */
  .modes__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Features: 2 columns */
  .features__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Problem cards: horizontal */
  .problem-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Pricing: 3 columns */
  .pricing__grid {
    grid-template-columns: repeat(3, 1fr);
    align-items: center;
  }

  .pricing-card--popular {
    transform: scale(1.05);
    z-index: 1;
  }

  .pricing-card--popular:hover {
    transform: scale(1.05) translateY(-6px);
  }

  /* Security: 2 columns */
  .security__grid {
    grid-template-columns: repeat(2, 1fr);
  }

  /* Footer horizontal */
  .footer__inner {
    flex-direction: row;
    justify-content: space-between;
    text-align: left;
  }

  .footer__links {
    order: 0;
  }
}

/* -------------------------------------------------------------------------
   1024px — Small desktops
   ------------------------------------------------------------------------- */
@media (min-width: 1024px) {
  .hero {
    padding-top: calc(var(--navbar-height) + 4rem);
  }

  .hero__inner {
    gap: var(--space-3xl);
  }

  .phone-mock {
    width: 340px;
  }

  /* Steps: 5 columns with connecting line */
  .steps {
    grid-template-columns: repeat(5, 1fr);
    gap: var(--space-lg);
    align-items: flex-start;
  }

  .steps::before {
    content: "";
    position: absolute;
    top: 32px;
    left: 10%;
    right: 10%;
    height: 2px;
    background: linear-gradient(90deg, var(--color-border), var(--color-primary), var(--color-border));
    z-index: 0;
  }

  .step__icon {
    position: relative;
    z-index: 1;
  }

  /* Features: 2x2 */
  .features__grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-xl);
  }

  /* Security: 3 columns */
  .security__grid {
    grid-template-columns: repeat(3, 1fr);
  }

  /* Comparison table - better spacing */
  .comparison__table th,
  .comparison__table td {
    padding: 1rem 1.25rem;
  }
}

/* -------------------------------------------------------------------------
   1280px — Large desktops
   ------------------------------------------------------------------------- */
@media (min-width: 1280px) {
  :root {
    --container-max: 1240px;
  }

  .hero__inner {
    gap: var(--space-4xl);
  }

  .phone-mock {
    width: 360px;
  }

  .phone-mock__chat {
    min-height: 400px;
  }

  .navbar__inner {
    padding-top: 1.2rem;
    padding-bottom: 1.2rem;
  }
}

/* =========================================================================
   ACCESSIBILITY & REDUCED MOTION
   ========================================================================= */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  html {
    scroll-behavior: auto;
  }
}

/* Focus visible for keyboard navigation */
:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 2px;
}

/* Screen reader only utility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

/* =========================================================================
   SELECTION STYLE
   ========================================================================= */
::selection {
  background: rgba(14, 165, 233, 0.2);
  color: var(--color-text);
}