/* ═══════════════════════════════════════════════════════════════
   COREX AI TUTOR — Design System
   Palette: Deep Indigo + Electric Violet + Warm Cream
   Fonts: Bricolage Grotesque (UI) + DM Serif Display (headings)
═══════════════════════════════════════════════════════════════ */

/* ── RESET & BASE ─────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:          #0B0B14;
  --bg-2:        #11111F;
  --bg-3:        #181828;
  --surface:     #1E1E32;
  --surface-2:   #252540;
  --border:      rgba(120, 100, 255, 0.15);
  --border-2:    rgba(120, 100, 255, 0.08);

  --violet:      #7B5EFF;
  --violet-light:#A48BFF;
  --violet-dim:  rgba(123, 94, 255, 0.18);
  --violet-glow: rgba(123, 94, 255, 0.35);

  --cream:       #F0EBE0;
  --cream-dim:   #B8B0A0;
  --white:       #FFFFFF;

  --text-1:      #F0EBE0;
  --text-2:      #9B95B0;
  --text-3:      #6B6580;

  --success:     #4ADE80;
  --radius-sm:   8px;
  --radius-md:   14px;
  --radius-lg:   22px;
  --radius-xl:   32px;

  --font-ui:     'Bricolage Grotesque', sans-serif;
  --font-display:'DM Serif Display', serif;

  --shadow-sm:   0 2px 12px rgba(0,0,0,0.3);
  --shadow-md:   0 8px 32px rgba(0,0,0,0.4);
  --shadow-lg:   0 20px 60px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 40px rgba(123, 94, 255, 0.25);
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-ui);
  background: var(--bg);
  color: var(--text-1);
  min-height: 100dvh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* ── PAGE SYSTEM ──────────────────────────────────────────── */
.page { display: none; }
.page.active { display: block; }

#page-chat {
  display: none;
  flex-direction: column;
  height: 100dvh;
  overflow: hidden;
}
#page-chat.active { display: flex; }

/* ── SCROLLBAR ────────────────────────────────────────────── */
::-webkit-scrollbar { width: 4px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--surface-2); border-radius: 4px; }

/* ═══════════════════════════════════════════════════════════
   LANDING PAGE
═══════════════════════════════════════════════════════════ */

/* ── NAV ──────────────────────────────────────────────────── */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 32px;
  background: rgba(11, 11, 20, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-2);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.logo-icon {
  font-size: 1.4rem;
  color: var(--violet-light);
  filter: drop-shadow(0 0 8px var(--violet));
}

.logo-text { color: var(--cream); }

.nav-cta {
  background: var(--violet);
  color: var(--white);
  border: none;
  padding: 10px 22px;
  border-radius: var(--radius-xl);
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  box-shadow: 0 0 20px var(--violet-glow);
}
.nav-cta:hover {
  background: var(--violet-light);
  transform: translateY(-1px);
  box-shadow: 0 4px 24px var(--violet-glow);
}

/* ── HERO ─────────────────────────────────────────────────── */
.hero {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 120px 24px 80px;
  position: relative;
  overflow: hidden;
}

/* Background grid */
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(123, 94, 255, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(123, 94, 255, 0.04) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 80% 80% at 50% 50%, black 30%, transparent 100%);
}

/* Radial glow */
.hero::after {
  content: '';
  position: absolute;
  top: 20%;
  left: 50%;
  transform: translateX(-50%);
  width: 600px;
  height: 400px;
  background: radial-gradient(ellipse, rgba(123, 94, 255, 0.15) 0%, transparent 70%);
  pointer-events: none;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--violet-dim);
  border: 1px solid var(--border);
  color: var(--violet-light);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 7px 16px;
  border-radius: var(--radius-xl);
  margin-bottom: 28px;
  position: relative;
  z-index: 1;
  animation: fadeSlideDown 0.6s ease both;
}

.badge-dot {
  width: 7px;
  height: 7px;
  background: var(--success);
  border-radius: 50%;
  box-shadow: 0 0 8px var(--success);
  animation: pulse 2s infinite;
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(2.8rem, 7vw, 5.5rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
  color: var(--cream);
  max-width: 800px;
  position: relative;
  z-index: 1;
  animation: fadeSlideDown 0.6s 0.1s ease both;
}

.hero-title em {
  font-style: italic;
  background: linear-gradient(135deg, var(--violet-light), #C4B0FF);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-sub {
  font-size: clamp(1rem, 2vw, 1.15rem);
  color: var(--text-2);
  max-width: 560px;
  line-height: 1.7;
  margin-top: 24px;
  position: relative;
  z-index: 1;
  animation: fadeSlideDown 0.6s 0.2s ease both;
}

.hero-actions {
  display: flex;
  align-items: center;
  gap: 20px;
  margin-top: 36px;
  flex-wrap: wrap;
  justify-content: center;
  position: relative;
  z-index: 1;
  animation: fadeSlideDown 0.6s 0.3s ease both;
}

.hero-note {
  font-size: 0.8rem;
  color: var(--text-3);
}

/* ── BUTTONS ──────────────────────────────────────────────── */
.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: var(--violet);
  color: var(--white);
  border: none;
  padding: 14px 28px;
  border-radius: var(--radius-xl);
  font-family: var(--font-ui);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.25s ease;
  box-shadow: 0 0 30px var(--violet-glow), var(--shadow-sm);
  position: relative;
  overflow: hidden;
}
.btn-primary::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.1), transparent);
  opacity: 0;
  transition: opacity 0.2s;
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 40px var(--violet-glow), var(--shadow-md);
}
.btn-primary:hover::before { opacity: 1; }
.btn-primary:active { transform: translateY(0); }

/* ── HERO PREVIEW CARD ────────────────────────────────────── */
.hero-preview {
  position: relative;
  margin-top: 64px;
  z-index: 1;
  animation: fadeSlideUp 0.8s 0.4s ease both;
}

.preview-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  width: min(380px, 90vw);
  box-shadow: var(--shadow-lg), var(--shadow-glow);
  text-align: left;
}

.preview-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border-2);
}

.preview-avatar {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--violet), #A48BFF);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  color: white;
  flex-shrink: 0;
  box-shadow: 0 0 16px var(--violet-glow);
}

.preview-name {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--cream);
}

.preview-status {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  color: var(--text-3);
}

.status-dot {
  width: 7px;
  height: 7px;
  background: var(--success);
  border-radius: 50%;
  box-shadow: 0 0 6px var(--success);
  animation: pulse 2s infinite;
}

.preview-bubble {
  background: var(--surface-2);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-md);
  border-top-left-radius: 4px;
  padding: 12px 16px;
  font-size: 0.9rem;
  line-height: 1.6;
  color: var(--text-1);
  margin-bottom: 14px;
}

.preview-suggestions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.preview-glow {
  position: absolute;
  bottom: -40px;
  left: 50%;
  transform: translateX(-50%);
  width: 300px;
  height: 80px;
  background: radial-gradient(ellipse, var(--violet-glow) 0%, transparent 70%);
  pointer-events: none;
}

/* ── SUGGESTION CHIPS ─────────────────────────────────────── */
.suggestion-chip {
  background: var(--violet-dim);
  border: 1px solid var(--border);
  color: var(--violet-light);
  padding: 7px 14px;
  border-radius: var(--radius-xl);
  font-family: var(--font-ui);
  font-size: 0.8rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
}
.suggestion-chip:hover {
  background: rgba(123, 94, 255, 0.3);
  border-color: var(--violet);
  transform: translateY(-1px);
}

/* ── FEATURES SECTION ─────────────────────────────────────── */
.features {
  padding: 100px 24px;
  max-width: 1100px;
  margin: 0 auto;
}

.features-header {
  text-align: center;
  margin-bottom: 60px;
}

.features-header h2 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4vw, 3rem);
  color: var(--cream);
  margin-bottom: 16px;
}

.features-header p {
  font-size: 1.05rem;
  color: var(--text-2);
  max-width: 520px;
  margin: 0 auto;
  line-height: 1.7;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}

.feature-card {
  background: var(--surface);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.feature-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, transparent, var(--violet), transparent);
  opacity: 0;
  transition: opacity 0.3s;
}

.feature-card:hover {
  border-color: var(--border);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md), 0 0 30px rgba(123, 94, 255, 0.1);
}
.feature-card:hover::before { opacity: 1; }

.feature-card--accent {
  background: linear-gradient(135deg, var(--surface), rgba(123, 94, 255, 0.08));
  border-color: var(--border);
}

.feature-icon {
  width: 52px;
  height: 52px;
  background: var(--violet-dim);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  color: var(--violet-light);
}

.feature-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--cream);
  margin-bottom: 10px;
  letter-spacing: -0.01em;
}

.feature-card p {
  font-size: 0.92rem;
  color: var(--text-2);
  line-height: 1.7;
}

/* ── TUTOR SECTION ────────────────────────────────────────── */
.tutor-section {
  padding: 100px 24px;
  background: var(--bg-2);
  border-top: 1px solid var(--border-2);
  border-bottom: 1px solid var(--border-2);
}

.tutor-content {
  max-width: 1100px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 80px;
  align-items: center;
}

.tutor-text h2 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 3.5vw, 2.8rem);
  color: var(--cream);
  line-height: 1.2;
  margin-bottom: 20px;
}

.tutor-text p {
  font-size: 1rem;
  color: var(--text-2);
  line-height: 1.75;
  margin-bottom: 32px;
}

.tutor-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin-bottom: 36px;
}

.tutor-list li {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.95rem;
  color: var(--text-1);
}

.tutor-list li svg {
  color: var(--success);
  flex-shrink: 0;
}

/* ── ORBIT VISUAL ─────────────────────────────────────────── */
.tutor-visual {
  display: flex;
  align-items: center;
  justify-content: center;
}

.subjects-orbit {
  position: relative;
  width: 320px;
  height: 320px;
}

.orbit-center {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 72px;
  height: 72px;
  background: linear-gradient(135deg, var(--violet), #A48BFF);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.8rem;
  color: white;
  box-shadow: 0 0 40px var(--violet-glow);
  z-index: 2;
}

.orbit-item {
  position: absolute;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-1);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 8px 16px;
  border-radius: var(--radius-xl);
  white-space: nowrap;
  animation: orbit-float 3s ease-in-out infinite;
}

.orbit-item--1 { top: 10px; left: 50%; transform: translateX(-50%); animation-delay: 0s; }
.orbit-item--2 { top: 30%; right: 0; animation-delay: 0.5s; }
.orbit-item--3 { bottom: 30%; right: 5%; animation-delay: 1s; }
.orbit-item--4 { bottom: 10px; left: 50%; transform: translateX(-50%); animation-delay: 1.5s; }
.orbit-item--5 { bottom: 30%; left: 0; animation-delay: 2s; }
.orbit-item--6 { top: 30%; left: 0; animation-delay: 2.5s; }

/* ── FOOTER ───────────────────────────────────────────────── */
.footer {
  padding: 48px 24px;
  text-align: center;
  border-top: 1px solid var(--border-2);
}

.footer-logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 10px;
}

.footer-tagline {
  font-size: 0.85rem;
  color: var(--text-3);
}

/* ═══════════════════════════════════════════════════════════
   CHAT PAGE
═══════════════════════════════════════════════════════════ */

/* ── CHAT HEADER ──────────────────────────────────────────── */
.chat-header {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 20px;
  background: var(--bg-2);
  border-bottom: 1px solid var(--border-2);
  flex-shrink: 0;
  backdrop-filter: blur(20px);
}

.back-btn, .clear-btn {
  width: 38px;
  height: 38px;
  background: var(--surface);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  color: var(--text-2);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  flex-shrink: 0;
}
.back-btn:hover, .clear-btn:hover {
  background: var(--surface-2);
  color: var(--text-1);
  border-color: var(--border);
}

.chat-header-info {
  display: flex;
  align-items: center;
  gap: 12px;
  flex: 1;
}

.chat-avatar {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--violet), #A48BFF);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  color: white;
  flex-shrink: 0;
  box-shadow: 0 0 14px var(--violet-glow);
}

.chat-name {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--cream);
}

.chat-status {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  color: var(--text-3);
}

/* ── MESSAGES ─────────────────────────────────────────────── */
.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: 24px 16px;
  display: flex;
  flex-direction: column;
  gap: 20px;
  scroll-behavior: smooth;
}

.chat-date-divider {
  text-align: center;
  font-size: 0.72rem;
  color: var(--text-3);
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  position: relative;
}
.chat-date-divider::before,
.chat-date-divider::after {
  content: '';
  position: absolute;
  top: 50%;
  width: 30%;
  height: 1px;
  background: var(--border-2);
}
.chat-date-divider::before { left: 0; }
.chat-date-divider::after { right: 0; }

/* ── MESSAGE BUBBLES ──────────────────────────────────────── */
.message {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  animation: messageIn 0.3s ease both;
  max-width: 100%;
}

.message--user {
  flex-direction: row-reverse;
}

.message-avatar {
  width: 34px;
  height: 34px;
  background: linear-gradient(135deg, var(--violet), #A48BFF);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.9rem;
  color: white;
  flex-shrink: 0;
  box-shadow: 0 0 10px var(--violet-glow);
  margin-top: 2px;
}

.message-body {
  display: flex;
  flex-direction: column;
  gap: 10px;
  max-width: calc(100% - 50px);
}

.message--user .message-body {
  align-items: flex-end;
}

.message-bubble {
  padding: 12px 16px;
  border-radius: var(--radius-md);
  font-size: 0.93rem;
  line-height: 1.65;
  word-break: break-word;
}

.message--ai .message-bubble {
  background: var(--surface);
  border: 1px solid var(--border-2);
  border-top-left-radius: 4px;
  color: var(--text-1);
}

.message--user .message-bubble {
  background: var(--violet);
  border-top-right-radius: 4px;
  color: var(--white);
  box-shadow: 0 4px 16px var(--violet-glow);
}

.message-suggestions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

/* ── TYPING INDICATOR ─────────────────────────────────────── */
.typing-indicator {
  display: flex;
  align-items: center;
  gap: 5px;
  padding: 14px 18px;
  background: var(--surface);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-md);
  border-top-left-radius: 4px;
  width: fit-content;
}

.typing-dot {
  width: 7px;
  height: 7px;
  background: var(--violet-light);
  border-radius: 50%;
  animation: typingBounce 1.2s infinite;
}
.typing-dot:nth-child(2) { animation-delay: 0.2s; }
.typing-dot:nth-child(3) { animation-delay: 0.4s; }

/* ── INPUT AREA ───────────────────────────────────────────── */
.chat-input-area {
  padding: 16px 16px 20px;
  background: var(--bg-2);
  border-top: 1px solid var(--border-2);
  flex-shrink: 0;
}

.chat-input-wrapper {
  display: flex;
  align-items: flex-end;
  gap: 10px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 10px 10px 10px 18px;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.chat-input-wrapper:focus-within {
  border-color: var(--violet);
  box-shadow: 0 0 0 3px var(--violet-dim);
}

.chat-input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  color: var(--text-1);
  font-family: var(--font-ui);
  font-size: 0.95rem;
  line-height: 1.5;
  resize: none;
  max-height: 140px;
  overflow-y: auto;
}

.chat-input::placeholder { color: var(--text-3); }

.send-btn {
  width: 40px;
  height: 40px;
  background: var(--violet);
  border: none;
  border-radius: var(--radius-md);
  color: white;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all 0.2s;
  box-shadow: 0 0 16px var(--violet-glow);
}
.send-btn:hover {
  background: var(--violet-light);
  transform: scale(1.05);
}
.send-btn:active { transform: scale(0.97); }
.send-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
}

.input-disclaimer {
  text-align: center;
  font-size: 0.72rem;
  color: var(--text-3);
  margin-top: 10px;
}

/* ═══════════════════════════════════════════════════════════
   ANIMATIONS
═══════════════════════════════════════════════════════════ */

@keyframes fadeSlideDown {
  from { opacity: 0; transform: translateY(-16px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes fadeSlideUp {
  from { opacity: 0; transform: translateY(24px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes messageIn {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50%       { opacity: 0.6; transform: scale(0.85); }
}

@keyframes typingBounce {
  0%, 60%, 100% { transform: translateY(0); }
  30%           { transform: translateY(-6px); }
}

@keyframes orbit-float {
  0%, 100% { transform: translateY(0); }
  50%       { transform: translateY(-6px); }
}

/* ═══════════════════════════════════════════════════════════
   RESPONSIVE
═══════════════════════════════════════════════════════════ */

/* ── PWA INSTALL BANNER ───────────────────────────────────────── */
.install-banner {
  position: fixed;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 9999;
  display: flex;
  align-items: center;
  gap: 12px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 14px 18px;
  box-shadow: var(--shadow-lg), var(--shadow-glow);
  width: min(420px, calc(100vw - 32px));
  animation: fadeSlideUp 0.4s ease both;
}

.install-banner-icon {
  font-size: 1.5rem;
  color: var(--violet-light);
  filter: drop-shadow(0 0 6px var(--violet));
  flex-shrink: 0;
}

.install-banner-text {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.install-banner-text strong {
  font-size: 0.9rem;
  color: var(--cream);
  font-weight: 700;
}

.install-banner-text span {
  font-size: 0.78rem;
  color: var(--text-2);
}

.install-banner-btn {
  background: var(--violet);
  color: white;
  border: none;
  padding: 8px 18px;
  border-radius: var(--radius-xl);
  font-family: var(--font-ui);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  flex-shrink: 0;
  transition: all 0.2s;
  box-shadow: 0 0 14px var(--violet-glow);
}
.install-banner-btn:hover {
  background: var(--violet-light);
  transform: translateY(-1px);
}

.install-banner-close {
  background: transparent;
  border: none;
  color: var(--text-3);
  font-size: 0.9rem;
  cursor: pointer;
  padding: 4px;
  flex-shrink: 0;
  transition: color 0.2s;
  line-height: 1;
}
.install-banner-close:hover { color: var(--text-1); }

@media (max-width: 768px) {
  .nav { padding: 14px 20px; }

  .hero { padding: 100px 20px 60px; }

  .tutor-content {
    grid-template-columns: 1fr;
    gap: 48px;
  }

  .tutor-visual { display: none; }

  .features { padding: 70px 20px; }
  .tutor-section { padding: 70px 20px; }

  .chat-messages { padding: 16px 12px; }
}

@media (max-width: 480px) {
  .hero-title { font-size: 2.4rem; }
  .features-grid { grid-template-columns: 1fr; }
  .preview-card { width: 100%; }
}