/**
 * Robotics & Mechatronics Club - Modern University Tech Design System
 * Deep Navy (#080d1a), Electric Cyan/Blue (#00d2ff, #0284c7), Energetic Amber (#f59e0b)
 */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500;600&family=Outfit:wght@500;600;700;800&display=swap');

:root {
  /* Colors - Modern University Tech Design System (Default: Modern Glow) */
  --bg-primary: #080d1a;
  --bg-secondary: #0d1527;
  --bg-surface: #131f38;
  --bg-surface-hover: #182847;
  --bg-elevated: #1a2a4c;
  --border-subtle: #1e3054;
  --border-strong: #2a4374;
  --border-focus: #00d2ff;

  --accent-cyan: #00d2ff;
  --accent-cyan-glow: rgba(0, 210, 255, 0.25);
  --accent-blue: #0284c7;
  --accent-blue-hover: #0369a1;
  --accent-amber: #f59e0b;
  --accent-amber-glow: rgba(245, 158, 11, 0.25);
  --accent-emerald: #10b981;
  --accent-emerald-glow: rgba(16, 185, 129, 0.25);
  --accent-rose: #f43f5e;

  /* Text */
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-accent: #38bdf8;

  /* Typography */
  --font-heading: 'Outfit', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Transitions & Shadows */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;

  --shadow-subtle: 0 4px 20px -2px rgba(0, 0, 0, 0.4);
  --shadow-elevated: 0 10px 30px -4px rgba(0, 0, 0, 0.6), 0 0 15px rgba(0, 210, 255, 0.08);
  --shadow-glow: 0 0 25px rgba(0, 210, 255, 0.35);

  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

/* Optional: Classical Mid-2010s Minimalist Theme (Activate by adding data-theme="classic" to <html>) */
[data-theme="classic"] {
  --bg-primary: #12161f;
  --bg-secondary: #171d28;
  --bg-surface: #1d2533;
  --bg-surface-hover: #242e3f;
  --bg-elevated: #212a39;
  --border-subtle: #293447;
  --border-strong: #36445b;
  --border-focus: #2563eb;

  --accent-cyan: #38bdf8;
  --accent-cyan-glow: none;
  --accent-blue: #2563eb;
  --accent-blue-hover: #1d4ed8;
  --accent-amber: #d97706;
  --accent-amber-glow: none;
  --accent-emerald: #059669;
  --accent-emerald-glow: none;
  --accent-rose: #e11d48;

  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #8b99ad;
  --text-accent: #38bdf8;

  --font-heading: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: 'JetBrains Mono', 'Consolas', monospace;

  --radius-sm: 2px;
  --radius-md: 3px;
  --radius-lg: 4px;
  --radius-full: 3px;

  --shadow-subtle: 0 1px 3px rgba(0, 0, 0, 0.25);
  --shadow-elevated: 0 2px 6px rgba(0, 0, 0, 0.35);
  --shadow-glow: none;

  --transition-fast: 0.12s ease;
  --transition-normal: 0.2s ease;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  overflow-x: hidden;
  max-width: 100vw;
  width: 100%;
}

body {
  font-family: var(--font-body);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
  max-width: 100vw;
  width: 100%;
  position: relative;
  background-image: 
    radial-gradient(ellipse at 15% 10%, rgba(2, 132, 199, 0.15) 0%, transparent 45%),
    radial-gradient(ellipse at 85% 25%, rgba(0, 210, 255, 0.1) 0%, transparent 40%),
    radial-gradient(circle at 50% 80%, rgba(245, 158, 11, 0.05) 0%, transparent 50%);
  background-attachment: fixed;
}

img, svg, video, canvas, audio, iframe, embed, object {
  max-width: 100%;
  height: auto;
}

input, select, textarea, button {
  max-width: 100%;
  box-sizing: border-box;
}

[data-theme="classic"] body {
  background-image: none;
}

/* Base Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  color: var(--text-primary);
  font-weight: 700;
  line-height: 1.25;
}

a {
  color: var(--accent-cyan);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: #7dd3fc;
  text-decoration: underline;
}

button {
  font-family: var(--font-body);
  cursor: pointer;
  border: none;
  outline: none;
}

/* Header & Top Bar */
.top-notice-bar {
  background: linear-gradient(90deg, #09152b 0%, #11254d 50%, #09152b 100%);
  border-bottom: 1px solid var(--border-subtle);
  font-size: 0.85rem;
  padding: 0.5rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--text-muted);
}

[data-theme="classic"] .top-notice-bar {
  background: var(--bg-secondary);
  font-size: 0.82rem;
  padding: 0.45rem 1.5rem;
}

.top-notice-left {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.status-dot-pulse {
  width: 8px;
  height: 8px;
  background-color: var(--accent-emerald);
  border-radius: 50%;
  box-shadow: 0 0 8px var(--accent-emerald);
  animation: pulse-glow 2s infinite;
}

[data-theme="classic"] .status-dot-pulse {
  box-shadow: none;
  animation: none;
}

@keyframes pulse-glow {
  0% { transform: scale(0.95); opacity: 0.7; }
  50% { transform: scale(1.2); opacity: 1; }
  100% { transform: scale(0.95); opacity: 0.7; }
}

.top-notice-right {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

.instructor-link {
  color: var(--accent-amber);
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

.instructor-link:hover {
  color: #fde047;
  text-decoration: none;
}

/* Header Branding */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(8, 13, 26, 0.88);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-subtle);
}

[data-theme="classic"] .site-header {
  background: var(--bg-secondary);
  backdrop-filter: none;
  -webkit-backdrop-filter: none;
}

.header-container {
  max-width: 1360px;
  margin: 0 auto;
  padding: 0.9rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.25rem;
}

.brand-wrapper {
  display: flex;
  align-items: center;
  gap: 1rem;
  text-decoration: none;
}

.brand-wrapper:hover {
  text-decoration: none;
}

.brand-emblem {
  width: 44px;
  height: 44px;
  background: linear-gradient(135deg, #0284c7 0%, #00d2ff 100%);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 0 16px var(--accent-cyan-glow);
  flex-shrink: 0;
}

[data-theme="classic"] .brand-emblem {
  width: 40px;
  height: 40px;
  background: var(--accent-blue);
  box-shadow: none;
  border-radius: var(--radius-sm);
}

.brand-emblem svg {
  width: 26px;
  height: 26px;
  fill: #ffffff;
}

.brand-titles h1 {
  font-size: 1.25rem;
  letter-spacing: -0.01em;
  color: #ffffff;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.club-title-tag {
  font-size: 0.65rem;
  padding: 0.15rem 0.45rem;
  background: rgba(0, 210, 255, 0.15);
  border: 1px solid var(--accent-cyan);
  border-radius: 4px;
  color: var(--accent-cyan);
  font-family: var(--font-mono);
  font-weight: 600;
  letter-spacing: 0.05em;
}

.brand-titles p {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* Nav Tabs */
.main-nav {
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.nav-tab-btn {
  padding: 0.65rem 1.1rem;
  background: transparent;
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.92rem;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
  border: 1px solid transparent;
}

.nav-tab-btn:hover {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.04);
}

.nav-tab-btn.active {
  color: #ffffff;
  background: var(--bg-surface);
  border-color: var(--border-strong);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}

.nav-counter-pill {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 0.1rem 0.45rem;
  border-radius: var(--radius-full);
  background: rgba(0, 210, 255, 0.18);
  color: var(--accent-cyan);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

/* User Auth Navigation Menu */
.user-auth-menu-wrapper {
  position: relative;
}

.user-auth-btn {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.85rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.85rem;
  font-weight: 600;
  transition: all var(--transition-fast);
}

.user-auth-btn:hover {
  background: var(--bg-surface-hover);
  border-color: var(--accent-cyan);
}

.user-auth-btn.is-instructor-active {
  border-color: rgba(245, 158, 11, 0.5);
  background: linear-gradient(135deg, rgba(19, 31, 56, 0.9) 0%, rgba(35, 26, 12, 0.5) 100%);
  box-shadow: 0 0 12px rgba(245, 158, 11, 0.15);
}

.auth-avatar {
  font-size: 1.15rem;
}

.auth-name {
  max-width: 130px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.verified-star {
  color: #fbbf24;
  font-size: 0.85rem;
}

.dropdown-chevron {
  font-size: 0.7rem;
  color: var(--text-muted);
}

.auth-dropdown-popover {
  position: absolute;
  top: calc(100% + 0.5rem);
  right: 0;
  background: var(--bg-secondary);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  min-width: 260px;
  padding: 0.85rem;
  box-shadow: var(--shadow-elevated);
  display: none;
  z-index: 150;
  animation: fadeIn 0.18s ease;
}

.auth-dropdown-popover.active {
  display: block;
}

.dropdown-header-block {
  padding-bottom: 0.65rem;
}

.dropdown-user-name {
  font-size: 0.95rem;
  font-weight: 700;
  color: #ffffff;
}

.dropdown-user-role {
  font-size: 0.78rem;
  color: var(--accent-cyan);
  font-weight: 600;
}

.dropdown-user-email {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.dropdown-divider {
  height: 1px;
  background: var(--border-subtle);
  margin: 0.6rem 0;
}

.dropdown-section-title {
  font-size: 0.72rem;
  text-transform: uppercase;
  color: var(--text-muted);
  font-weight: 600;
  letter-spacing: 0.05em;
  margin-bottom: 0.4rem;
}

.dropdown-item-btn {
  width: 100%;
  text-align: left;
  padding: 0.45rem 0.65rem;
  background: transparent;
  color: var(--text-secondary);
  font-size: 0.82rem;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all var(--transition-fast);
}

.dropdown-item-btn:hover {
  background: var(--bg-surface-hover);
  color: #ffffff;
}

.btn-danger-text {
  color: var(--accent-rose) !important;
}

.btn-danger-text:hover {
  background: rgba(244, 63, 94, 0.15) !important;
}

/* Sign In Modal */
.auth-tabs-row {
  display: flex;
  gap: 0.5rem;
  border-bottom: 1px solid var(--border-subtle);
  margin-bottom: 1.5rem;
}

.auth-tab-btn {
  padding: 0.5rem 1rem;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.88rem;
  font-weight: 600;
  border-bottom: 2px solid transparent;
  transition: all var(--transition-fast);
}

.auth-tab-btn.active {
  color: var(--accent-cyan);
  border-bottom-color: var(--accent-cyan);
}

.auth-tab-panel {
  display: none;
}

.auth-tab-panel.active {
  display: block;
}

.btn-link-reset {
  background: none;
  border: none;
  color: var(--accent-cyan);
  font-size: 0.82rem;
  cursor: pointer;
  padding: 0;
  text-decoration: underline;
  transition: color var(--transition-fast);
}

.btn-link-reset:hover {
  color: #ffffff;
}

.auth-divider {
  display: flex;
  align-items: center;
  text-align: center;
  margin: 1.15rem 0;
  color: var(--text-muted);
  font-size: 0.76rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.auth-divider::before,
.auth-divider::after {
  content: '';
  flex: 1;
  border-bottom: 1px solid var(--border-subtle);
}

.auth-divider span {
  padding: 0 0.75rem;
}

.btn-google-auth {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  width: 100%;
  padding: 0.72rem 1rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: var(--radius-sm);
  color: #ffffff;
  font-size: 0.92rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-google-auth:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: rgba(255, 255, 255, 0.38);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.3);
  transform: translateY(-1px);
}

.btn-google-auth:active {
  transform: translateY(0);
}

.avatar-picker-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 0.5rem;
  margin-top: 0.35rem;
}

.avatar-pick-option {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.25rem;
  font-size: 1.35rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.avatar-pick-option:hover {
  background: var(--bg-surface-hover);
  border-color: var(--accent-cyan);
  transform: scale(1.08);
}

.avatar-pick-option.selected {
  border-color: var(--accent-cyan);
  background: rgba(0, 210, 255, 0.15);
  box-shadow: 0 0 10px rgba(0, 210, 255, 0.3);
}

.nav-revised-pill {
  font-size: 0.72rem;
  background: rgba(16, 185, 129, 0.2);
  color: #10b981;
  border: 1px solid rgba(16, 185, 129, 0.4);
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-full);
  font-weight: 700;
  margin-left: 0.25rem;
}

.role-badge-tag {
  font-size: 0.72rem;
  padding: 0.2rem 0.55rem;
  border-radius: var(--radius-full);
  background: rgba(0, 210, 255, 0.15);
  color: var(--accent-cyan);
  font-weight: 600;
}

.role-badge-instructor {
  background: rgba(245, 158, 11, 0.2);
  color: #fbbf24;
}

/* User Profile & Dashboard Modal Styles */
.profile-hero-block {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  padding: 1.25rem;
  background: linear-gradient(135deg, rgba(19, 31, 56, 0.9) 0%, rgba(13, 21, 39, 0.95) 100%);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  margin-bottom: 1.25rem;
}

.profile-hero-avatar-box {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  background: var(--bg-surface);
  border: 2px solid var(--accent-cyan);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.2rem;
  flex-shrink: 0;
  box-shadow: 0 0 16px rgba(0, 210, 255, 0.25);
}

.profile-hero-info {
  flex: 1;
}

.profile-tabs-row {
  display: flex;
  gap: 0.5rem;
  border-bottom: 1px solid var(--border-subtle);
  margin-bottom: 1.25rem;
}

.profile-tab-btn {
  padding: 0.55rem 1rem;
  background: transparent;
  color: var(--text-muted);
  font-size: 0.88rem;
  font-weight: 600;
  border-bottom: 2px solid transparent;
  transition: all var(--transition-fast);
}

.profile-tab-btn:hover {
  color: var(--text-primary);
}

.profile-tab-btn.active {
  color: var(--accent-cyan);
  border-bottom-color: var(--accent-cyan);
}

.profile-tab-panel {
  display: none;
}

.profile-tab-panel.active {
  display: block;
  animation: fadeIn 0.2s ease;
}

.progress-overview-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  padding: 1.25rem;
}

.profile-progress-track {
  width: 100%;
  height: 10px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-top: 0.5rem;
}

.profile-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-cyan), #10b981);
  border-radius: var(--radius-full);
  transition: width 0.3s ease;
  box-shadow: 0 0 12px rgba(16, 185, 129, 0.5);
}

.profile-pdf-grid {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.profile-pdf-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.85rem 1.15rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  transition: all var(--transition-fast);
}

.profile-pdf-card.is-revised {
  border-color: rgba(16, 185, 129, 0.5);
  background: rgba(16, 185, 129, 0.05);
}

.profile-pdf-left {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.profile-pdf-icon {
  font-size: 1.4rem;
}

.profile-pdf-title {
  font-size: 0.92rem;
  font-weight: 600;
  color: #ffffff;
  margin: 0;
}

.profile-pdf-sub {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin: 0.15rem 0 0 0;
}

/* Hero Section */
.hero-banner {
  max-width: 1360px;
  margin: 1.5rem auto 0 auto;
  padding: 0 1.5rem;
}

.hero-glass-box {
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  padding: 1.9rem 2.2rem;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-subtle);
}

.hero-glass-box {
  background: linear-gradient(135deg, rgba(19, 31, 56, 0.8) 0%, rgba(13, 21, 39, 0.9) 100%);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  padding: 2.2rem 2.5rem;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-elevated);
}

[data-theme="classic"] .hero-glass-box {
  background: var(--bg-surface);
  padding: 1.9rem 2.2rem;
  box-shadow: var(--shadow-subtle);
}

.hero-glass-box::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 450px;
  height: 100%;
  background: radial-gradient(circle at 80% 20%, rgba(0, 210, 255, 0.12) 0%, transparent 70%);
  pointer-events: none;
}

[data-theme="classic"] .hero-glass-box::before {
  display: none;
}

.hero-content {
  position: relative;
  z-index: 2;
  max-width: 860px;
}

.hero-pill-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.85rem;
  flex-wrap: wrap;
}

.hero-tag {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 0.25rem 0.65rem;
  border-radius: var(--radius-full);
  background: rgba(2, 132, 199, 0.2);
  color: #38bdf8;
  border: 1px solid rgba(56, 189, 248, 0.3);
}

[data-theme="classic"] .hero-tag {
  font-size: 0.74rem;
  letter-spacing: 0.06em;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-sm);
  background: rgba(37, 99, 235, 0.15);
}

.hero-title {
  font-size: 2.3rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 0.85rem;
  line-height: 1.2;
}

.hero-title .text-gradient {
  background: linear-gradient(90deg, #38bdf8 0%, #00d2ff 60%, #34d399 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

[data-theme="classic"] .hero-title {
  font-size: 2.1rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.25;
}

[data-theme="classic"] .hero-title .text-gradient {
  background: none;
  -webkit-background-clip: unset;
  -webkit-text-fill-color: #ffffff;
  color: #ffffff;
}

.hero-lead {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 1.5rem;
}

.hero-meta-bar {
  display: flex;
  align-items: center;
  gap: 2rem;
  flex-wrap: wrap;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 1.25rem;
}

.hero-meta-item {
  display: flex;
  align-items: center;
  gap: 0.65rem;
}

.hero-meta-icon {
  font-size: 1.2rem;
}

.hero-meta-text {
  font-size: 0.85rem;
}

.hero-meta-text span {
  display: block;
  color: var(--text-muted);
  font-size: 0.75rem;
}

.hero-meta-text strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* Main Container & Tab Views */
.main-wrapper {
  max-width: 1360px;
  margin: 1.75rem auto 3rem auto;
  padding: 0 1.5rem;
  flex: 1;
  width: 100%;
}

.view-section {
  display: none;
  animation: fadeIn 0.3s ease;
}

.view-section.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Button Component System */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.65rem 1.25rem;
  border-radius: var(--radius-md);
  font-size: 0.9rem;
  font-weight: 600;
  transition: all var(--transition-fast);
  text-decoration: none;
}

.btn:hover {
  text-decoration: none;
}

.btn-primary {
  background: var(--accent-blue);
  color: #ffffff;
  border: 1px solid rgba(0, 0, 0, 0.2);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}

.btn-primary:hover {
  background: var(--accent-blue-hover);
  color: #ffffff;
  border-color: rgba(0, 0, 0, 0.3);
}

.btn-primary {
  background: linear-gradient(135deg, #0284c7 0%, #00b4d8 100%);
  color: #ffffff;
  box-shadow: 0 4px 14px rgba(2, 132, 199, 0.35);
  border: none;
}

.btn-primary:hover {
  background: linear-gradient(135deg, #0369a1 0%, #0096c7 100%);
  box-shadow: 0 6px 18px rgba(0, 210, 255, 0.45);
  transform: translateY(-1px);
}

[data-theme="classic"] .btn-primary {
  background: var(--accent-blue);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
  border: 1px solid rgba(0, 0, 0, 0.2);
}

[data-theme="classic"] .btn-primary:hover {
  background: var(--accent-blue-hover);
  transform: none;
  box-shadow: var(--shadow-subtle);
}

.btn-secondary {
  background: var(--bg-surface);
  color: var(--text-secondary);
  border: 1px solid var(--border-strong);
}

.btn-secondary:hover {
  background: var(--bg-surface-hover);
  color: var(--text-primary);
  border-color: var(--accent-cyan);
}

.btn-outline {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-subtle);
}

.btn-outline:hover {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
}

.btn-accent {
  background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
  color: #000000;
  font-weight: 700;
  box-shadow: 0 4px 14px var(--accent-amber-glow);
  border: none;
}

.btn-accent:hover {
  background: linear-gradient(135deg, #fbbf24 0%, #b45309 100%);
  transform: translateY(-1px);
}

[data-theme="classic"] .btn-accent {
  background: var(--accent-amber);
  color: #ffffff;
  font-weight: 600;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
  border: 1px solid rgba(0, 0, 0, 0.2);
}

[data-theme="classic"] .btn-accent:hover {
  background: #b45309;
  transform: none;
}

.btn-sm {
  padding: 0.45rem 0.85rem;
  font-size: 0.82rem;
}

.btn-block {
  width: 100%;
}

/* Badge System */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.22rem 0.6rem;
  border-radius: var(--radius-full);
  white-space: nowrap;
  flex-shrink: 0;
  line-height: 1.25;
}

.badge-lab {
  background: rgba(245, 158, 11, 0.15);
  color: #fbbf24;
  border: 1px solid rgba(245, 158, 11, 0.35);
}

.badge-zoom {
  background: rgba(56, 189, 248, 0.15);
  color: #38bdf8;
  border: 1px solid rgba(56, 189, 248, 0.35);
}

.badge-lecture {
  background: rgba(148, 163, 184, 0.15);
  color: #cbd5e1;
  border: 1px solid rgba(148, 163, 184, 0.3);
}

.badge-solved {
  background: rgba(16, 185, 129, 0.2);
  color: #34d399;
  border: 1px solid rgba(16, 185, 129, 0.4);
}

.badge-open {
  background: rgba(148, 163, 184, 0.12);
  color: var(--text-muted);
  border: 1px solid var(--border-subtle);
}

.badge-instructor {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.25) 0%, rgba(217, 119, 6, 0.2) 100%);
  color: #fde047;
  border: 1px solid rgba(253, 224, 71, 0.4);
  box-shadow: 0 0 10px rgba(245, 158, 11, 0.2);
}

.badge-student {
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-secondary);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.badge-verified-answer {
  background: rgba(0, 210, 255, 0.15);
  color: var(--accent-cyan);
  border: 1px solid rgba(0, 210, 255, 0.3);
}

/* Modals Framework */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(3, 7, 18, 0.78);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
  opacity: 0;
  transition: opacity var(--transition-normal);
}

.modal-overlay.active {
  display: flex;
  opacity: 1;
}

.modal-dialog {
  background: var(--bg-secondary);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 860px;
  max-height: 90vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: var(--shadow-elevated);
  position: relative;
  animation: modalPop 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

@keyframes modalPop {
  from { transform: scale(0.96) translateY(10px); opacity: 0; }
  to { transform: scale(1) translateY(0); opacity: 1; }
}

.modal-close-btn {
  position: absolute;
  top: 1.25rem;
  right: 1.25rem;
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-secondary);
  width: 32px;
  height: 32px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  transition: all var(--transition-fast);
  z-index: 10;
}

.modal-close-btn:hover {
  background: rgba(244, 63, 94, 0.2);
  color: var(--accent-rose);
}

.modal-scroll-body {
  overflow-y: auto;
  padding: 2rem;
}

/* Toast Notifications */
.toast-container {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
  pointer-events: none;
}

.toast {
  background: var(--bg-surface);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  padding: 0.85rem 1.25rem;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  min-width: 280px;
  max-width: 420px;
  color: var(--text-primary);
  font-size: 0.9rem;
  pointer-events: auto;
  transition: all 0.3s ease;
}

.toast-success {
  border-left: 4px solid var(--accent-emerald);
}

.toast-info {
  border-left: 4px solid var(--accent-cyan);
}

.toast-warning {
  border-left: 4px solid var(--accent-amber);
}

.toast-error {
  border-left: 4px solid var(--accent-rose);
}

.toast-fade-out {
  opacity: 0;
  transform: translateY(10px);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border-subtle);
  background: var(--bg-secondary);
  padding: 2.5rem 1.5rem 1.5rem 1.5rem;
  margin-top: auto;
}

.footer-inner {
  max-width: 1360px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 2.5rem;
}

.footer-col h4 {
  font-size: 0.95rem;
  color: #ffffff;
  margin-bottom: 0.85rem;
  letter-spacing: 0.02em;
}

.footer-col p {
  color: var(--text-muted);
  font-size: 0.85rem;
  line-height: 1.6;
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: 0.5rem;
}

.footer-links a {
  color: var(--text-muted);
  font-size: 0.85rem;
}

.footer-links a:hover {
  color: var(--accent-cyan);
}

.footer-bottom-row {
  max-width: 1360px;
  margin: 2rem auto 0 auto;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border-subtle);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--text-muted);
  flex-wrap: wrap;
  gap: 1rem;
}

/* Form Row Grid System */
.form-row-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-bottom: 1rem;
}

@media (max-width: 640px) {
  .form-row-grid {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
}

/* ==============================================
   RESPONSIVE DESIGN (TABLET & MOBILE)
   ============================================== */
@media (max-width: 900px) {
  .top-notice-bar {
    padding: 0.45rem 1rem;
    font-size: 0.78rem;
    flex-wrap: wrap;
    gap: 0.5rem;
  }

  .header-container {
    flex-wrap: wrap;
    padding: 0.65rem 1rem;
    gap: 0.65rem;
  }

  .brand-wrapper {
    gap: 0.65rem;
  }

  .brand-emblem {
    width: 38px;
    height: 38px;
  }

  .brand-titles h1 {
    font-size: 1.12rem;
  }

  .brand-titles p {
    font-size: 0.74rem;
  }

  .main-nav {
    order: 3;
    width: 100%;
    display: flex;
    gap: 0.35rem;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    padding: 0.35rem 0 0.15rem 0;
    border-top: 1px solid rgba(255, 255, 255, 0.06);
  }

  .main-nav::-webkit-scrollbar {
    display: none;
  }

  .nav-tab-btn {
    flex-shrink: 0;
    white-space: nowrap;
    padding: 0.45rem 0.8rem;
    font-size: 0.82rem;
    gap: 0.35rem;
  }

  .hero-banner {
    padding: 0 1rem;
    margin-top: 1.25rem;
  }

  .hero-glass-box {
    padding: 1.5rem 1.25rem;
  }

  .hero-title {
    font-size: 1.75rem;
  }

  .hero-meta-bar {
    gap: 1.25rem;
  }

  .main-wrapper {
    padding: 0 1rem;
    margin: 1.25rem auto 2.5rem auto;
  }

  .footer-inner {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }
}

@media (max-width: 640px) {
  .top-notice-bar {
    padding: 0.35rem 0.75rem;
    font-size: 0.72rem;
    flex-direction: column;
    text-align: center;
    gap: 0.25rem;
  }

  .top-notice-left, .top-notice-right {
    justify-content: center;
    flex-wrap: wrap;
    gap: 0.4rem;
  }

  .header-container {
    padding: 0.5rem 0.75rem;
    gap: 0.5rem;
  }

  .brand-wrapper {
    gap: 0.5rem;
    max-width: 60%;
  }

  .brand-emblem {
    width: 34px;
    height: 34px;
  }

  .brand-emblem svg {
    width: 20px;
    height: 20px;
  }

  .brand-titles h1 {
    font-size: 0.98rem;
    line-height: 1.15;
  }

  .club-title-tag {
    display: none;
  }

  .brand-titles p {
    display: none;
  }

  .header-actions {
    gap: 0.35rem;
  }

  .header-actions .btn {
    padding: 0.4rem 0.65rem;
    font-size: 0.78rem;
  }

  .user-auth-btn {
    padding: 0.35rem 0.55rem;
    font-size: 0.78rem;
  }

  .auth-name {
    max-width: 85px;
  }

  .auth-avatar {
    font-size: 1rem;
  }

  .hero-banner {
    padding: 0 0.75rem;
    margin-top: 0.85rem;
  }

  .hero-glass-box {
    padding: 1.25rem 0.85rem;
    border-radius: var(--radius-md);
  }

  .hero-title {
    font-size: 1.4rem;
    line-height: 1.25;
    margin-bottom: 0.6rem;
  }

  .hero-lead {
    font-size: 0.85rem;
    line-height: 1.5;
    margin-bottom: 0.85rem;
  }

  .hero-pill-row {
    gap: 0.35rem;
    margin-bottom: 0.6rem;
  }

  .hero-meta-bar {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem 0.5rem;
    padding-top: 0.75rem;
  }

  .hero-meta-item {
    gap: 0.45rem;
  }

  .hero-meta-icon {
    font-size: 1.1rem;
  }

  .hero-meta-text {
    font-size: 0.78rem;
  }

  .hero-meta-text span {
    font-size: 0.68rem;
  }

  .hero-meta-text strong {
    font-size: 0.78rem;
  }

  .main-wrapper {
    padding: 0 0.75rem;
    margin: 1rem auto 2rem auto;
  }

  /* Modals Mobile Bottom Sheet / Fitted Dialog */
  .modal-overlay {
    padding: 0;
    align-items: flex-end;
  }

  .modal-dialog {
    max-height: 94vh;
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    width: 100%;
    margin-bottom: 0;
  }

  .modal-scroll-body {
    padding: 1.25rem 0.85rem;
  }

  .modal-close-btn {
    top: 0.75rem;
    right: 0.75rem;
    width: 28px;
    height: 28px;
    font-size: 0.95rem;
  }

  .auth-dropdown-popover {
    position: fixed;
    top: auto;
    bottom: 0;
    left: 0;
    right: 0;
    width: 100%;
    min-width: 100%;
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    box-shadow: 0 -8px 30px rgba(0, 0, 0, 0.6);
  }

  .toast-container {
    left: 1rem;
    right: 1rem;
    bottom: 1rem;
  }

  .toast {
    width: 100%;
  }
}