/* ════════════════════════════════════════════════════════════════
   Study Buddy — Global Design System
   Modern EdTech · Indigo / Purple primary palette
   ════════════════════════════════════════════════════════════════ */

/* ──────────────────────────────────────────────────────────────
   1. GOOGLE FONTS are loaded in base.html <head>
   ────────────────────────────────────────────────────────────── */

/* ──────────────────────────────────────────────────────────────
   2. DESIGN TOKENS
   ────────────────────────────────────────────────────────────── */
:root {
  /* Primary — Indigo / Deep Purple */
  --sb-primary-50:    #eef2ff;
  --sb-primary-100:   #e0e7ff;
  --sb-primary-200:   #c7d2fe;
  --sb-primary-400:   #818cf8;
  --sb-primary-500:   #6366f1;
  --sb-primary-600:   #4f46e5;
  --sb-primary-700:   #4338ca;
  --sb-primary-900:   #1e1b4b;

  /* Secondary — Blue */
  --sb-blue-400:      #60a5fa;
  --sb-blue-500:      #3b82f6;
  --sb-blue-600:      #2563eb;

  /* Accent — Cyan */
  --sb-cyan-400:      #22d3ee;
  --sb-cyan-500:      #06b6d4;

  /* Accent — Yellow */
  --sb-yellow-400:    #facc15;
  --sb-yellow-500:    #eab308;

  /* Accent — Soft Orange */
  --sb-orange-400:    #fb923c;
  --sb-orange-500:    #f97316;

  /* Neutrals */
  --sb-gray-50:       #f9fafb;
  --sb-gray-100:      #f3f4f6;
  --sb-gray-200:      #e5e7eb;
  --sb-gray-300:      #d1d5db;
  --sb-gray-400:      #9ca3af;
  --sb-gray-500:      #6b7280;
  --sb-gray-600:      #4b5563;
  --sb-gray-700:      #374151;
  --sb-gray-800:      #1f2937;
  --sb-gray-900:      #111827;

  /* Background scale */
  --sb-bg:            #ffffff;
  --sb-bg-lavender:   #f5f3ff;
  --sb-bg-blue:       #eff6ff;
  --sb-surface:       #ffffff;
  --sb-surface-alt:   #f8faff;

  /* Semantic */
  --sb-text:          #1e1b4b;
  --sb-text-body:     #374151;
  --sb-text-muted:    #6b7280;
  --sb-text-dim:      #9ca3af;
  --sb-border:        #e0e7ff;
  --sb-border-mid:    #c7d2fe;

  /* Typography */
  --sb-font-heading:  'Poppins', 'Inter', system-ui, sans-serif;
  --sb-font-body:     'Inter', system-ui, sans-serif;

  /* Spacing scale */
  --sb-space-1:   4px;
  --sb-space-2:   8px;
  --sb-space-3:   12px;
  --sb-space-4:   16px;
  --sb-space-5:   20px;
  --sb-space-6:   24px;
  --sb-space-8:   32px;
  --sb-space-10:  40px;
  --sb-space-12:  48px;
  --sb-space-16:  64px;

  /* Border radius */
  --sb-r-sm:   6px;
  --sb-r-md:   10px;
  --sb-r-lg:   16px;
  --sb-r-xl:   24px;
  --sb-r-full: 9999px;

  /* Shadows */
  --sb-shadow-sm:  0 1px 3px rgba(99,102,241,.08), 0 1px 2px rgba(99,102,241,.06);
  --sb-shadow-md:  0 4px 16px rgba(99,102,241,.10), 0 2px 6px rgba(99,102,241,.07);
  --sb-shadow-lg:  0 10px 36px rgba(99,102,241,.14), 0 4px 12px rgba(99,102,241,.09);
  --sb-shadow-nav: 0 2px 20px rgba(99,102,241,.12), 0 1px 6px rgba(99,102,241,.08);

  /* Gradients */
  --sb-gradient-primary: linear-gradient(135deg, var(--sb-primary-600) 0%, var(--sb-blue-600) 100%);
  --sb-gradient-cta:     linear-gradient(135deg, var(--sb-primary-500) 0%, var(--sb-blue-500) 60%, var(--sb-cyan-500) 100%);
  --sb-gradient-hero:    linear-gradient(135deg, var(--sb-bg-lavender) 0%, var(--sb-bg-blue) 100%);
  --sb-gradient-text:    linear-gradient(90deg, var(--sb-primary-600), var(--sb-blue-500));

  /* Transitions */
  --sb-transition-fast:  all 0.15s ease;
  --sb-transition-base:  all 0.25s ease;
  --sb-transition-slow:  all 0.4s ease;

  /* Navbar */
  --sb-nav-h: 68px;
  --sb-nav-h-mobile: 60px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--sb-font-body);
  color: var(--sb-text-body);
  background: var(--sb-bg);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }
ul, ol { list-style: none; }
input, select, textarea { font-family: inherit; }

/* ──────────────────────────────────────────────────────────────
   4. SCROLLBAR
   ────────────────────────────────────────────────────────────── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: var(--sb-border-mid);
  border-radius: var(--sb-r-full);
}
::-webkit-scrollbar-thumb:hover { background: var(--sb-primary-400); }

/* ──────────────────────────────────────────────────────────────
   5. TYPOGRAPHY UTILITIES
   ────────────────────────────────────────────────────────────── */
.sb-heading {
  font-family: var(--sb-font-heading);
  font-weight: 700;
  color: var(--sb-text);
  line-height: 1.2;
}
.sb-gradient-text {
  background: var(--sb-gradient-text);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* ──────────────────────────────────────────────────────────────
   6. LAYOUT UTILITIES
   ────────────────────────────────────────────────────────────── */
.hidden { display: none !important; }
.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;
}
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--sb-space-6);
}

/* ══════════════════════════════════════════════════════════════
   7. NAVBAR COMPONENT
   ══════════════════════════════════════════════════════════════ */

.sb-navbar {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  height: var(--sb-nav-h);
  background: rgba(7, 9, 14, 0.75);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s ease, box-shadow 0.3s ease, background 0.3s ease;
  will-change: box-shadow;
}

.sb-navbar.scrolled {
  border-bottom-color: rgba(255, 255, 255, 0.08);
  box-shadow: var(--sb-shadow-nav);
  background: rgba(7, 9, 14, 0.92);
}

.sb-navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
  max-width: 1240px;
  margin: 0 auto;
  padding: 0 var(--sb-space-6);
  gap: var(--sb-space-6);
}

/* Logo */
.sb-navbar__logo {
  display: flex;
  align-items: center;
  gap: var(--sb-space-2);
  text-decoration: none;
  flex-shrink: 0;
  transition: var(--sb-transition-fast);
}
.sb-navbar__logo:hover { opacity: 0.85; }

.sb-logo-icon {
  position: relative;
  width: 38px;
  height: 38px;
  flex-shrink: 0;
}
.sb-logo-icon svg {
  width: 38px;
  height: 38px;
  display: block;
}

.sb-logo-wordmark {
  display: flex;
  flex-direction: column;
  line-height: 1;
}
.sb-logo-name {
  font-family: var(--sb-font-heading);
  font-size: 1.125rem;
  font-weight: 800;
  background: var(--sb-gradient-text);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.02em;
}
.sb-logo-tagline {
  font-family: var(--sb-font-body);
  font-size: 0.6rem;
  font-weight: 500;
  color: var(--sb-text-muted);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-top: 2px;
}

/* Center nav links */
.sb-navbar__nav {
  display: flex;
  align-items: center;
  gap: var(--sb-space-1);
  flex: 1;
  justify-content: center;
}

.sb-nav-link {
  position: relative;
  font-family: var(--sb-font-body);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--sb-text-muted);
  text-decoration: none;
  padding: var(--sb-space-2) var(--sb-space-3);
  border-radius: var(--sb-r-md);
  transition: color 0.2s ease, background 0.2s ease;
  white-space: nowrap;
}
.sb-nav-link::after {
  content: '';
  position: absolute;
  bottom: 4px;
  left: 50%;
  width: 0;
  height: 2px;
  background: var(--sb-gradient-primary);
  border-radius: var(--sb-r-full);
  transform: translateX(-50%);
  transition: width 0.25s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.sb-nav-link:hover {
  color: var(--sb-primary-600);
  background: var(--sb-primary-50);
}
.sb-nav-link:hover::after { width: 60%; }
.sb-nav-link.active {
  color: var(--sb-primary-600);
  font-weight: 600;
  background: var(--sb-primary-50);
}
.sb-nav-link.active::after { width: 60%; }

/* Action buttons */
.sb-navbar__actions {
  display: flex;
  align-items: center;
  gap: var(--sb-space-2);
  flex-shrink: 0;
}

/* Login — ghost */
.sb-btn-login {
  font-family: var(--sb-font-body);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--sb-primary-600);
  padding: 8px 18px;
  border: 1.5px solid var(--sb-primary-200);
  border-radius: var(--sb-r-full);
  background: transparent;
  transition: var(--sb-transition-fast);
  cursor: pointer;
  white-space: nowrap;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.sb-btn-login:hover {
  background: var(--sb-primary-50);
  border-color: var(--sb-primary-400);
  color: var(--sb-primary-700);
  transform: translateY(-1px);
  box-shadow: var(--sb-shadow-sm);
}
.sb-btn-login:active { transform: translateY(0); }

/* CTA — gradient */
.sb-btn-cta {
  font-family: var(--sb-font-heading);
  font-size: 0.875rem;
  font-weight: 600;
  color: #ffffff;
  padding: 9px 22px;
  border-radius: var(--sb-r-full);
  background: var(--sb-gradient-cta);
  border: none;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  white-space: nowrap;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.sb-btn-cta::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(120deg, transparent 30%, rgba(255,255,255,0.25) 50%, transparent 70%);
  transform: translateX(-100%);
  transition: transform 0.5s ease;
}
.sb-btn-cta:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(99, 102, 241, 0.45);
}
.sb-btn-cta:hover::before { transform: translateX(100%); }
.sb-btn-cta:active { transform: translateY(0); }
.sb-btn-cta .cta-icon { transition: transform 0.2s ease; }
.sb-btn-cta:hover .cta-icon { transform: translateX(2px); }

/* User Greeting Badge (when logged in on public site) */
.sb-user-greeting {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 5px 14px 5px 6px;
  background: var(--sb-primary-50);
  border: 1px solid var(--sb-primary-200);
  border-radius: var(--sb-r-full);
  text-decoration: none;
  color: var(--sb-text);
  font-size: 0.85rem;
  transition: all 0.2s ease;
  white-space: nowrap;
}
.sb-user-greeting:hover {
  background: #ede9fe;
  border-color: var(--sb-primary-400);
  transform: translateY(-1px);
}
.user-greeting-avatar {
  width: 26px;
  height: 26px;
  border-radius: 50%;
  background: var(--sb-gradient-cta);
  color: #ffffff;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.78rem;
  font-weight: 700;
  font-family: var(--sb-font-heading);
}
.user-greeting-text {
  font-family: var(--sb-font-body);
  color: var(--sb-text);
}
.user-greeting-text strong {
  color: var(--sb-primary-700);
}

.sb-mobile-user-greeting {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  background: var(--sb-primary-50);
  border: 1px solid var(--sb-primary-200);
  border-radius: var(--sb-r-lg);
  font-size: 0.95rem;
  color: var(--sb-text);
  margin-bottom: 6px;
}
.sb-mobile-user-greeting strong {
  color: var(--sb-primary-700);
}

/* Hamburger */
.sb-hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 40px;
  height: 40px;
  padding: 8px;
  border-radius: var(--sb-r-md);
  background: transparent;
  border: 1.5px solid var(--sb-border);
  cursor: pointer;
  gap: 5px;
  transition: var(--sb-transition-fast);
  flex-shrink: 0;
}
.sb-hamburger:hover {
  background: var(--sb-primary-50);
  border-color: var(--sb-primary-200);
}
.sb-hamburger__bar {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--sb-text);
  border-radius: var(--sb-r-full);
  transition: transform 0.3s cubic-bezier(0.68, -0.55, 0.265, 1.55),
              opacity 0.2s ease,
              width 0.2s ease;
  transform-origin: center;
}
.sb-hamburger.is-open .sb-hamburger__bar:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.sb-hamburger.is-open .sb-hamburger__bar:nth-child(2) {
  opacity: 0;
  width: 0;
}
.sb-hamburger.is-open .sb-hamburger__bar:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Mobile menu */
.sb-mobile-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background: rgba(255, 255, 255, 0.98);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--sb-border);
  box-shadow: 0 8px 30px rgba(99, 102, 241, 0.12);
  overflow: hidden;
  max-height: 0;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.3s ease;
  opacity: 0;
}
.sb-mobile-menu.is-open {
  max-height: 480px;
  opacity: 1;
}
.sb-mobile-menu__inner {
  padding: var(--sb-space-4) var(--sb-space-6) var(--sb-space-6);
  display: flex;
  flex-direction: column;
  gap: var(--sb-space-1);
}
.sb-mobile-nav-link {
  font-family: var(--sb-font-body);
  font-size: 1rem;
  font-weight: 500;
  color: var(--sb-text-body);
  padding: var(--sb-space-3) var(--sb-space-4);
  border-radius: var(--sb-r-md);
  display: block;
  transition: var(--sb-transition-fast);
  text-decoration: none;
}
.sb-mobile-nav-link:hover,
.sb-mobile-nav-link.active {
  color: var(--sb-primary-600);
  background: var(--sb-primary-50);
  font-weight: 600;
}
.sb-mobile-divider {
  height: 1px;
  background: var(--sb-border);
  margin: var(--sb-space-3) 0;
}
.sb-mobile-actions {
  display: flex;
  flex-direction: column;
  gap: var(--sb-space-2);
  padding-top: var(--sb-space-1);
}
.sb-mobile-actions .sb-btn-login,
.sb-mobile-actions .sb-btn-cta {
  width: 100%;
  justify-content: center;
  text-align: center;
}

/* ══════════════════════════════════════════════════════════════
   8. RESPONSIVE
   ══════════════════════════════════════════════════════════════ */
@media (max-width: 900px) {
  .sb-navbar__nav { display: none; }
  .sb-navbar__actions .sb-btn-login,
  .sb-navbar__actions .sb-btn-cta { display: none; }
  .sb-hamburger { display: flex; }
  .sb-mobile-menu { display: block; }
}

@media (max-width: 480px) {
  .sb-navbar { height: var(--sb-nav-h-mobile); }
  .sb-navbar__inner {
    padding: 0 var(--sb-space-4);
    gap: var(--sb-space-3);
  }
  .sb-logo-tagline { display: none; }
  .sb-logo-name { font-size: 1rem; }
  .sb-logo-icon { width: 32px; height: 32px; }
  .sb-logo-icon svg { width: 32px; height: 32px; }
  .sb-mobile-menu__inner {
    padding: var(--sb-space-3) var(--sb-space-4) var(--sb-space-5);
  }
}

/* ══════════════════════════════════════════════════════════════
   9. PAGE CONTENT OFFSET
   ══════════════════════════════════════════════════════════════ */
.sb-page-content {
  min-height: calc(100vh - var(--sb-nav-h));
}