/* ============================
   CSS Variables & Reset
   ============================ */
:root {
  --primary: #3B5BDB;
  --primary-dark: #2f4ac4;
  --primary-light: #e8edff;
  --danger: #e03131;
  --danger-light: #fff5f5;
  --success: #2f9e44;
  --success-light: #ebfbee;
  --warning: #e67700;
  --warning-light: #fff9db;
  --gray-50: #f8f9fa;
  --gray-100: #f1f3f5;
  --gray-200: #e9ecef;
  --gray-300: #dee2e6;
  --gray-400: #ced4da;
  --gray-500: #adb5bd;
  --gray-600: #868e96;
  --gray-700: #495057;
  --gray-800: #343a40;
  --gray-900: #212529;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius: 8px;
  --radius-lg: 12px;
  --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --nav-height: 60px;
}

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

html { font-size: 16px; }

body {
  font-family: var(--font);
  background: var(--gray-50);
  color: var(--gray-900);
  min-height: 100vh;
}

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

/* ============================
   Navbar
   ============================ */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-height);
  background: #fff;
  border-bottom: 1px solid var(--gray-200);
  display: flex;
  align-items: center;
  padding: 0 24px;
  gap: 24px;
  box-shadow: var(--shadow-sm);
}

.navbar-brand {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 8px;
}

.navbar-brand .logo-icon {
  font-size: 1.4rem;
}

.navbar-nav {
  display: flex;
  align-items: center;
  gap: 4px;
  flex: 1;
}

.navbar-nav a {
  padding: 6px 14px;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--gray-700);
  text-decoration: none;
  transition: background 0.15s, color 0.15s;
}

.navbar-nav a:hover { background: var(--gray-100); color: var(--gray-900); }
.navbar-nav a.active { background: var(--primary-light); color: var(--primary); }

.navbar-end {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-left: auto;
}

.navbar-user {
  font-size: 0.875rem;
  color: var(--gray-600);
}

.navbar-user strong { color: var(--gray-800); }

/* ============================
   Buttons
   ============================ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 8px 16px;
  border: none;
  border-radius: var(--radius);
  font-family: var(--font);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, opacity 0.15s, transform 0.1s;
  white-space: nowrap;
}

.btn:active { transform: scale(0.97); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }

.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--primary-dark); }

.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover:not(:disabled) { background: #c02020; }

.btn-success { background: var(--success); color: #fff; }
.btn-success:hover:not(:disabled) { background: #267a38; }

.btn-outline {
  background: transparent;
  color: var(--gray-700);
  border: 1px solid var(--gray-300);
}
.btn-outline:hover:not(:disabled) { background: var(--gray-100); }

.btn-sm { padding: 5px 10px; font-size: 0.8rem; }
.btn-lg { padding: 12px 24px; font-size: 1rem; }
.btn-full { width: 100%; }

/* ============================
   Forms
   ============================ */
.form-group { display: flex; flex-direction: column; gap: 6px; }

.form-label {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--gray-700);
}

.form-control {
  width: 100%;
  padding: 9px 12px;
  border: 1px solid var(--gray-300);
  border-radius: var(--radius);
  font-family: var(--font);
  font-size: 0.9rem;
  color: var(--gray-900);
  background: #fff;
  transition: border-color 0.15s, box-shadow 0.15s;
}

.form-control:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(59, 91, 219, 0.15);
}

.form-control::placeholder { color: var(--gray-500); }

select.form-control { cursor: pointer; }

/* ============================
   Alerts / Messages
   ============================ */
.alert {
  padding: 12px 16px;
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-weight: 500;
  border: 1px solid transparent;
}

.alert-error {
  background: var(--danger-light);
  color: var(--danger);
  border-color: #ffc9c9;
}

.alert-success {
  background: var(--success-light);
  color: var(--success);
  border-color: #b2f2bb;
}

.alert-warning {
  background: var(--warning-light);
  color: var(--warning);
  border-color: #ffe066;
}

.alert { display: none; }
.alert.visible { display: block; }

/* ============================
   Cards
   ============================ */
.card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}

/* ============================
   Page container
   ============================ */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

.page-header {
  padding: 32px 0 24px;
}

.page-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--gray-900);
}

.page-subtitle {
  font-size: 0.9rem;
  color: var(--gray-600);
  margin-top: 4px;
}

/* ============================
   Badge
   ============================ */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  border-radius: 99px;
  font-size: 0.75rem;
  font-weight: 600;
}

.badge-primary { background: var(--primary-light); color: var(--primary); }
.badge-success { background: var(--success-light); color: var(--success); }
.badge-danger { background: var(--danger-light); color: var(--danger); }
.badge-warning { background: var(--warning-light); color: var(--warning); }
.badge-gray { background: var(--gray-100); color: var(--gray-600); }

/* ============================
   Loading spinner
   ============================ */
.spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid var(--gray-300);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}

.spinner-lg {
  width: 40px;
  height: 40px;
  border-width: 3px;
}

@keyframes spin { to { transform: rotate(360deg); } }

.loading-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 60px 24px;
  color: var(--gray-500);
  font-size: 0.9rem;
}

/* ============================
   Empty state
   ============================ */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 60px 24px;
  text-align: center;
}

.empty-icon { font-size: 3rem; opacity: 0.4; }
.empty-title { font-size: 1.1rem; font-weight: 600; color: var(--gray-700); }
.empty-desc { font-size: 0.875rem; color: var(--gray-500); }

/* ============================
   Login page
   ============================ */
.login-page {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background: linear-gradient(135deg, #e8edff 0%, #f8f9fa 100%);
}

.login-card {
  width: 100%;
  max-width: 400px;
  padding: 40px;
  background: #fff;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
}

.login-logo {
  text-align: center;
  margin-bottom: 32px;
}

.login-logo .logo-icon { font-size: 3rem; }
.login-logo h1 { font-size: 1.5rem; font-weight: 700; color: var(--primary); margin-top: 8px; }
.login-logo p { font-size: 0.875rem; color: var(--gray-500); margin-top: 4px; }

.login-form { display: flex; flex-direction: column; gap: 20px; }

.login-hint {
  margin-top: 24px;
  padding: 12px;
  background: var(--gray-50);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  font-size: 0.8rem;
  color: var(--gray-600);
}

.login-hint strong { display: block; margin-bottom: 6px; color: var(--gray-700); }
.login-hint table { width: 100%; border-collapse: collapse; }
.login-hint td { padding: 2px 4px; }
.login-hint code {
  background: var(--gray-200);
  border-radius: 3px;
  padding: 1px 4px;
  font-size: 0.78rem;
}

/* ============================
   Book catalog
   ============================ */
.toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  padding: 16px 0 20px;
}

.search-group {
  display: flex;
  gap: 6px;
  flex: 1;
  min-width: 220px;
}

.search-group .form-control { flex: 1; }

.books-meta {
  font-size: 0.875rem;
  color: var(--gray-500);
  padding: 0 0 16px;
}

.books-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 20px;
  padding-bottom: 48px;
}

/* Book card */
.book-card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  transition: box-shadow 0.2s, transform 0.2s;
}

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

.book-cover {
  height: 140px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

.book-cover-icon {
  font-size: 3rem;
  opacity: 0.7;
}

.book-cover-img img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  position: absolute;
  top: 0;
  left: 0;
  border-radius: inherit;
}

.book-body {
  padding: 14px;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.book-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--gray-900);
  line-height: 1.3;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.book-author {
  font-size: 0.8rem;
  color: var(--gray-600);
}

.book-meta {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-top: 4px;
}

.book-copies {
  font-size: 0.78rem;
  color: var(--gray-500);
  margin-left: auto;
}

.book-copies.none { color: var(--danger); }

.book-footer {
  padding: 10px 14px;
  border-top: 1px solid var(--gray-100);
}

/* ============================
   My Books page
   ============================ */
.loans-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
  padding-bottom: 48px;
}

.loan-card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  padding: 18px 20px;
  display: flex;
  align-items: center;
  gap: 16px;
  box-shadow: var(--shadow-sm);
}

.loan-cover {
  width: 50px;
  height: 70px;
  border-radius: 4px;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}

.loan-info { flex: 1; min-width: 0; }
.loan-title { font-weight: 600; font-size: 1rem; color: var(--gray-900); }
.loan-author { font-size: 0.875rem; color: var(--gray-600); margin-top: 2px; }

.loan-dates {
  display: flex;
  gap: 20px;
  margin-top: 8px;
  font-size: 0.8rem;
  color: var(--gray-500);
}

.loan-dates .due-date.overdue { color: var(--danger); font-weight: 600; }
.loan-actions { flex-shrink: 0; }

/* ============================
   Admin panel
   ============================ */
.tabs {
  display: flex;
  gap: 4px;
  border-bottom: 2px solid var(--gray-200);
  margin-bottom: 24px;
}

.tab-btn {
  padding: 10px 20px;
  border: none;
  background: transparent;
  font-family: var(--font);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--gray-600);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: color 0.15s;
}

.tab-btn:hover { color: var(--gray-900); }
.tab-btn.active { color: var(--primary); border-bottom-color: var(--primary); }

.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* Table */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
}

.data-table th {
  text-align: left;
  padding: 10px 14px;
  font-weight: 600;
  color: var(--gray-700);
  background: var(--gray-50);
  border-bottom: 2px solid var(--gray-200);
  white-space: nowrap;
}

.data-table td {
  padding: 12px 14px;
  border-bottom: 1px solid var(--gray-100);
  color: var(--gray-800);
  vertical-align: middle;
}

.data-table tbody tr:hover { background: var(--gray-50); }

.data-table .actions { display: flex; gap: 6px; }

/* Add book form */
.add-form {
  background: var(--gray-50);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  padding: 24px;
  margin-bottom: 24px;
}

.add-form h3 { font-size: 1rem; font-weight: 600; margin-bottom: 18px; }

.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
}

.form-grid .form-group.full { grid-column: 1 / -1; }
.form-actions { display: flex; gap: 10px; margin-top: 20px; }

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 200;
  display: none;
}

.modal-overlay.visible { display: flex; }

.modal {
  background: #fff;
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 24px;
  border-bottom: 1px solid var(--gray-200);
}

.modal-title { font-size: 1.1rem; font-weight: 600; }

.modal-close {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.4rem;
  color: var(--gray-500);
  line-height: 1;
  padding: 2px 6px;
  border-radius: var(--radius);
}

.modal-close:hover { background: var(--gray-100); color: var(--gray-900); }
.modal-body { padding: 24px; }
.modal-footer { padding: 16px 24px; border-top: 1px solid var(--gray-200); display: flex; gap: 10px; justify-content: flex-end; }

/* ============================
   Responsive
   ============================ */
@media (max-width: 600px) {
  .navbar { padding: 0 16px; gap: 12px; }
  .container { padding: 0 16px; }
  .books-grid { grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 14px; }
  .toolbar { flex-direction: column; align-items: stretch; }
  .loan-card { flex-direction: column; align-items: flex-start; }
  .loan-actions { align-self: stretch; }
  .loan-actions .btn { width: 100%; }
}