/* ==========================================================
 * FairShare - Modern, Mobile-First Design System
 * ========================================================== */

:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  
  /* Color Palette */
  --bg-primary: #f8fafc;
  --bg-surface: #ffffff;
  --bg-surface-hover: #f1f5f9;
  --bg-sidebar: #0f172a;
  --text-sidebar: #94a3b8;
  --text-sidebar-active: #ffffff;
  
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  
  --border-color: #e2e8f0;
  --border-focus: #3b82f6;
  
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #eff6ff;
  
  --success: #10b981;
  --success-light: #ecfdf5;
  --success-text: #047857;
  
  --danger: #ef4444;
  --danger-light: #fef2f2;
  --danger-text: #b91c1c;
  
  --warning: #f59e0b;
  --warning-light: #fffbeb;
  --warning-text: #b45309;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.04);
  
  --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Dark Mode Variables */
[data-theme="dark"] {
  --bg-primary: #0b0f19;
  --bg-surface: #131b2e;
  --bg-surface-hover: #1e293b;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-light: #64748b;
  --border-color: #1e293b;
  --primary-light: #1e3a8a;
  --success-light: #064e3b;
  --success-text: #34d399;
  --danger-light: #7f1d1d;
  --danger-text: #f87171;
}

/* Base Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-main);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  text-decoration: none;
  color: var(--primary-hover);
}

/* App Layout Grid */
.app-container {
  display: flex;
  min-height: 100vh;
}

.app-sidebar {
  width: 260px;
  background-color: var(--bg-sidebar);
  color: var(--text-sidebar);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  z-index: 40;
}

.sidebar-header {
  padding: 24px;
  display: flex;
  align-items: center;
  gap: 12px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.brand-logo {
  font-size: 20px;
  font-weight: 800;
  color: #ffffff;
  display: flex;
  align-items: center;
  gap: 8px;
}

.brand-badge {
  background: #3b82f6;
  color: #fff;
  font-size: 11px;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 600;
}

.sidebar-nav {
  padding: 20px 12px;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  border-radius: var(--radius-sm);
  color: var(--text-sidebar);
  font-weight: 500;
  font-size: 14px;
  transition: var(--transition);
}

.nav-link:hover {
  background: rgba(255, 255, 255, 0.06);
  color: var(--text-sidebar-active);
}

.nav-link.active {
  background: var(--primary);
  color: #ffffff;
}

.sidebar-footer {
  padding: 16px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.user-snippet {
  display: flex;
  align-items: center;
  gap: 10px;
  overflow: hidden;
}

.user-avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: #3b82f6;
  color: #ffffff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
  flex-shrink: 0;
  object-fit: cover;
}

.user-info {
  line-height: 1.2;
  overflow: hidden;
}

.user-name {
  color: #ffffff;
  font-size: 14px;
  font-weight: 600;
  white-space: nowrap;
  text-overflow: ellipsis;
  overflow: hidden;
}

.user-email {
  color: var(--text-sidebar);
  font-size: 12px;
  white-space: nowrap;
  text-overflow: ellipsis;
  overflow: hidden;
}

/* Main Content Area */
.app-main {
  flex: 1;
  margin-left: 260px;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.top-navbar {
  height: 64px;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-color);
  padding: 0 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 30;
}

.page-title {
  font-size: 20px;
  font-weight: 700;
  color: var(--text-main);
}

.top-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

.content-wrapper {
  padding: 28px;
  flex: 1;
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
}

/* Dashboard Cards & Layout */
.balance-hero {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
  margin-bottom: 28px;
}

.card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

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

.balance-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.balance-card.net {
  background: linear-gradient(135deg, #1e293b, #0f172a);
  color: #ffffff;
  border: none;
}

.balance-label {
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.balance-card.net .balance-label {
  color: #94a3b8;
}

.balance-amount {
  font-size: 28px;
  font-weight: 800;
}

.amount-positive {
  color: var(--success);
}

.amount-negative {
  color: var(--danger);
}

.amount-neutral {
  color: var(--text-muted);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 14px;
  font-weight: 600;
  padding: 10px 18px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: var(--transition);
  line-height: 1;
}

.btn-primary {
  background: var(--primary);
  color: #ffffff;
}

.btn-primary:hover {
  background: var(--primary-hover);
  color: #ffffff;
}

.btn-success {
  background: var(--success);
  color: #ffffff;
}

.btn-success:hover {
  background: #059669;
  color: #ffffff;
}

.btn-danger {
  background: var(--danger);
  color: #ffffff;
}

.btn-danger:hover {
  background: #dc2626;
  color: #ffffff;
}

.btn-outline {
  background: transparent;
  border-color: var(--border-color);
  color: var(--text-main);
}

.btn-outline:hover {
  background: var(--bg-surface-hover);
  border-color: #cbd5e1;
}

.btn-sm {
  padding: 6px 12px;
  font-size: 13px;
}

.btn-lg {
  padding: 14px 24px;
  font-size: 16px;
  border-radius: var(--radius-md);
}

.btn-block {
  width: 100%;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/* Form Styles */
.form-group {
  margin-bottom: 18px;
}

.form-label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 6px;
}

.form-control {
  width: 100%;
  padding: 10px 14px;
  font-size: 14px;
  font-family: inherit;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  color: var(--text-main);
  transition: var(--transition);
}

.form-control:focus {
  outline: none;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.15);
}

textarea.form-control {
  min-height: 80px;
  resize: vertical;
}

/* 4-Digit OTP Input Box */
.otp-container {
  display: flex;
  justify-content: center;
  gap: 14px;
  margin: 24px 0;
}

.otp-box {
  width: 56px;
  height: 64px;
  text-align: center;
  font-size: 28px;
  font-weight: 700;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-surface);
  color: var(--text-main);
  transition: var(--transition);
}

.otp-box:focus {
  border-color: var(--primary);
  outline: none;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.12);
}

/* Groups List & Cards */
.groups-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

.group-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: var(--transition);
}

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

.group-card-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}

.group-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: var(--primary-light);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  font-weight: 700;
}

/* Expense List */
.expense-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px;
  border-bottom: 1px solid var(--border-color);
  transition: var(--transition);
  cursor: pointer;
}

.expense-item:last-child {
  border-bottom: none;
}

.expense-item:hover {
  background: var(--bg-surface-hover);
}

.expense-meta {
  display: flex;
  align-items: center;
  gap: 14px;
}

.category-badge {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  background: #f1f5f9;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
}

.expense-info h4 {
  font-size: 15px;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 2px;
}

.expense-sub {
  font-size: 12px;
  color: var(--text-muted);
}

.expense-amount-box {
  text-align: right;
}

.expense-total {
  font-size: 16px;
  font-weight: 700;
  color: var(--text-main);
}

.expense-share {
  font-size: 12px;
  font-weight: 500;
}

/* Badges & Pills */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 3px 8px;
  font-size: 11px;
  font-weight: 600;
  border-radius: var(--radius-full);
}

.badge-success {
  background: var(--success-light);
  color: var(--success-text);
}

.badge-danger {
  background: var(--danger-light);
  color: var(--danger-text);
}

.badge-neutral {
  background: #f1f5f9;
  color: #475569;
}

/* Modals */
.modal-backdrop {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 50;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition);
}

.modal-backdrop.show {
  opacity: 1;
  visibility: visible;
}

.modal-dialog {
  background: var(--bg-surface);
  border-radius: var(--radius-lg);
  max-width: 540px;
  width: 90%;
  max-height: 90vh;
  overflow-y: auto;
  padding: 24px;
  box-shadow: var(--shadow-lg);
  transform: scale(0.95);
  transition: var(--transition);
}

.modal-backdrop.show .modal-dialog {
  transform: scale(1);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.modal-title {
  font-size: 18px;
  font-weight: 700;
}

.btn-close {
  background: none;
  border: none;
  font-size: 20px;
  color: var(--text-muted);
  cursor: pointer;
}

/* Toast Notifications */
.toast-container {
  position: fixed;
  top: 20px;
  right: 20px;
  z-index: 60;
  display: flex;
  flex-direction: column;
  gap: 10px;
  max-width: 360px;
  width: 90%;
}

.toast {
  background: var(--bg-surface);
  color: var(--text-main);
  padding: 14px 18px;
  border-radius: var(--radius-md);
  border-left: 4px solid var(--primary);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
  animation: slideIn 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.toast-success { border-left-color: var(--success); }
.toast-error { border-left-color: var(--danger); }
.toast-info { border-left-color: var(--primary); }

@keyframes slideIn {
  from { transform: translateX(100%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}

/* Floating Action Button (Mobile) */
.fab-btn {
  position: fixed;
  bottom: 84px;
  right: 20px;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--primary);
  color: #ffffff;
  display: none;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  box-shadow: var(--shadow-lg);
  z-index: 35;
  border: none;
  cursor: pointer;
  transition: var(--transition);
}

.fab-btn:hover {
  transform: scale(1.06);
}

/* Bottom Navigation (Mobile) */
.bottom-nav {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: 64px;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-color);
  z-index: 40;
  justify-content: space-around;
  align-items: center;
}

.bottom-nav-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 600;
  text-decoration: none;
}

.bottom-nav-item.active {
  color: var(--primary);
}

.bottom-nav-item svg {
  width: 22px;
  height: 22px;
}

/* Empty States */
.empty-state {
  text-align: center;
  padding: 48px 24px;
}

.empty-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 16px;
  color: var(--text-light);
}

.empty-title {
  font-size: 16px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 6px;
}

.empty-desc {
  font-size: 14px;
  color: var(--text-muted);
  max-width: 320px;
  margin: 0 auto 20px;
}

/* Auth Pages Centering */
.auth-wrapper {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  background: var(--bg-primary);
}

.auth-card {
  max-width: 440px;
  width: 100%;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 36px;
  box-shadow: var(--shadow-md);
}

.auth-header {
  text-align: center;
  margin-bottom: 28px;
}

.auth-title {
  font-size: 24px;
  font-weight: 800;
  color: var(--text-main);
  margin-bottom: 6px;
}

.auth-subtitle {
  font-size: 14px;
  color: var(--text-muted);
}

/* Responsive Media Queries */
@media (max-width: 768px) {
  .app-sidebar {
    display: none;
  }
  .app-main {
    margin-left: 0;
    padding-bottom: 74px;
  }
  .bottom-nav {
    display: flex;
  }
  .fab-btn {
    display: flex;
  }
  .content-wrapper {
    padding: 16px;
  }
  .top-navbar {
    padding: 0 16px;
  }
  .balance-hero {
    grid-template-columns: 1fr;
  }
  .otp-box {
    width: 48px;
    height: 56px;
    font-size: 24px;
  }
}