/* ═══════════════════════════════════════════════
   Engineering Library – Public Stylesheet v2
   ═══════════════════════════════════════════════ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');
@import url('https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.5.0/css/all.min.css');

:root {
  --el-primary:        #6c3fc5;
  --el-primary-dark:   #5530a8;
  --el-primary-light:  #f0ebff;
  --el-primary-mid:    #e0d4fc;
  --el-accent:         #8b5cf6;
  --el-green:          #059669;
  --el-green-bg:       #d1fae5;
  --el-surface:        #ffffff;
  --el-bg:             #f7f5ff;
  --el-bg2:            #ede9fa;
  --el-border:         #ddd6f3;
  --el-text:           #1a1030;
  --el-text-muted:     #6b5f8a;
  --el-shadow-sm:      0 1px 4px rgba(108,63,197,.07), 0 1px 2px rgba(0,0,0,.04);
  --el-shadow-md:      0 4px 16px rgba(108,63,197,.10), 0 2px 6px rgba(0,0,0,.05);
  --el-shadow-lg:      0 12px 36px rgba(108,63,197,.15), 0 4px 12px rgba(0,0,0,.06);
  --el-radius:         14px;
  --el-radius-sm:      8px;
  --el-transition:     .2s ease;
  --el-font:           'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* ── Reset ── */
.el-library-root *, .el-library-root *::before, .el-library-root *::after {
  box-sizing: border-box; margin: 0; padding: 0;
}
.el-library-root {
  font-family: var(--el-font);
  color: var(--el-text);
  background: transparent;
}

/* ═══════════════════════════════════
   HERO  – full width, light purple
   ═══════════════════════════════════ */
.el-hero {
  width: 100%;
  background: linear-gradient(140deg, #ede9fa 0%, #ddd4f8 40%, #e8e0fb 100%);
  padding: 72px 32px 64px;
  text-align: center;
  position: relative;
  overflow: hidden;
  border-bottom: 1px solid var(--el-border);
}
.el-hero::before {
  content: '';
  position: absolute; inset: 0;
  background-image: radial-gradient(circle at 20% 50%, rgba(108,63,197,.08) 0%, transparent 60%),
                    radial-gradient(circle at 80% 20%, rgba(139,92,246,.06) 0%, transparent 50%);
  pointer-events: none;
}
.el-hero-inner { position: relative; max-width: 640px; margin: 0 auto; }
.el-hero-icon {
  width: 72px; height: 72px;
  background: var(--el-primary);
  border-radius: 20px;
  display: flex; align-items: center; justify-content: center;
  margin: 0 auto 20px;
  box-shadow: 0 8px 24px rgba(108,63,197,.3);
}
.el-hero-icon i { font-size: 1.8rem; color: #fff; }
.el-hero-title {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  color: var(--el-primary-dark);
  letter-spacing: -.5px;
  margin-bottom: 10px;
  line-height: 1.15;
}
.el-hero-sub {
  display: none; /* removed as requested */
}

/* ═══════════════════════════════════
   SEARCH + FILTER TRIGGER  (not sticky)
   ═══════════════════════════════════ */
.el-search-bar-wrap {
  background: var(--el-surface);
  border-bottom: 1px solid var(--el-border);
  padding: 18px 0;
  width: 100%;
}
.el-search-bar-inner {
  width: 85%;
  max-width: 1400px;
  margin: 0 auto;
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}
@media (max-width: 900px) { .el-search-bar-inner { width: 95%; } }
@media (max-width: 600px) { .el-search-bar-inner { width: 100%; padding: 0 16px; } }

.el-search-group {
  position: relative;
  flex: 1 1 260px;
  min-width: 200px;
}
.el-search-group i.el-search-icon {
    display: none !important;
  position: absolute;
  right: 14px; top: 50%;
  transform: translateY(-50%);
  color: var(--el-text-muted);
  font-size: .9rem;
  pointer-events: none;
  z-index: 1;
}
.el-search-input {
  width: 100%;
  padding: 11px 40px 11px 52px;
  border: 2px solid var(--el-border);
  border-radius: var(--el-radius-sm);
  font-size: .95rem;
  font-family: var(--el-font);
  background: var(--el-bg);
  color: var(--el-text);
  transition: border-color var(--el-transition), box-shadow var(--el-transition);
  outline: none;
}
.el-search-input:focus {
  border-color: var(--el-primary);
  box-shadow: 0 0 0 3px rgba(108,63,197,.12);
  background: #fff;
}
.el-search-input::placeholder { color: var(--el-text-muted); }
.el-clear-search {
  position: absolute;
  right: 10px; top: 50%;
  transform: translateY(-50%);
  background: none; border: none; cursor: pointer;
  color: var(--el-text-muted);
  width: 24px; height: 24px;
  display: flex; align-items: center; justify-content: center;
  border-radius: 50%;
  transition: background var(--el-transition);
  visibility: hidden;
}
.el-clear-search.visible { visibility: visible; }
.el-clear-search:hover { background: var(--el-bg2); color: var(--el-primary); }

.el-filter-trigger {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  background: var(--el-primary-light);
  border: 2px solid var(--el-primary-mid);
  border-radius: var(--el-radius-sm);
  color: var(--el-primary);
  font-size: .9rem;
  font-weight: 600;
  font-family: var(--el-font);
  cursor: pointer;
  transition: all var(--el-transition);
  white-space: nowrap;
  flex-shrink: 0;
}
.el-filter-trigger:hover, .el-filter-trigger.active {
  background: var(--el-primary);
  border-color: var(--el-primary);
  color: #fff;
}
.el-filter-badge {
  background: var(--el-primary);
  color: #fff;
  font-size: .7rem;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: 10px;
  min-width: 18px;
  text-align: center;
  display: none;
}
.el-filter-trigger.active .el-filter-badge,
.el-filter-trigger .el-filter-badge.visible { display: inline-block; }
.el-filter-trigger.active .el-filter-badge { background: rgba(255,255,255,.3); }

/* Active filters pills */
.el-active-filters {
  width: 85%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 10px 0 0;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.el-active-filters:empty { display: none; }
@media (max-width: 900px) { .el-active-filters { width: 95%; } }
@media (max-width: 600px) { .el-active-filters { width: 100%; padding: 10px 16px 0; } }
.el-filter-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--el-primary-light);
  border: 1px solid var(--el-primary-mid);
  color: var(--el-primary);
  font-size: .8rem;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 20px;
  cursor: pointer;
  transition: all var(--el-transition);
}
.el-filter-pill:hover { background: var(--el-primary); color: #fff; }
.el-filter-pill i { font-size: .7rem; }

/* ═══════════════════════════════════
   FILTER SIDEBAR  (slide-in panel)
   ═══════════════════════════════════ */
.el-sidebar-overlay {
  display: none;
  position: fixed; inset: 0;
  background: rgba(26,16,48,.45);
  backdrop-filter: blur(3px);
  z-index: 9000;
}
.el-sidebar-overlay.open { display: block; }

.el-filter-sidebar {
  position: fixed;
  top: 0; right: -360px;
  width: 340px; max-width: 100vw;
  height: 100%;
  background: var(--el-surface);
  z-index: 9001;
  box-shadow: -8px 0 40px rgba(108,63,197,.18);
  transition: right .3s cubic-bezier(.4,0,.2,1);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.el-filter-sidebar.open { right: 0; }

.el-sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 22px;
  border-bottom: 1px solid var(--el-border);
  background: var(--el-primary-light);
  flex-shrink: 0;
}
.el-sidebar-header h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--el-primary-dark);
  display: flex; align-items: center; gap: 8px;
}
.el-sidebar-close {
  width: 32px; height: 32px;
  background: none; border: none; cursor: pointer;
  color: var(--el-primary);
  font-size: 1rem;
  display: flex; align-items: center; justify-content: center;
  border-radius: 50%;
  transition: background var(--el-transition);
}
.el-sidebar-close:hover { background: var(--el-primary-mid); }

.el-sidebar-body {
  flex: 1;
  overflow-y: auto;
  padding: 20px;
}
.el-sidebar-body::-webkit-scrollbar { width: 5px; }
.el-sidebar-body::-webkit-scrollbar-thumb { background: var(--el-primary-mid); border-radius: 4px; }

.el-filter-group {
  margin-bottom: 28px;
}
.el-filter-group-title {
  font-size: .8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .7px;
  color: var(--el-primary);
  margin-bottom: 12px;
  display: flex; align-items: center; gap: 6px;
}
.el-checkbox-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.el-checkbox-item {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 8px 10px;
  border-radius: var(--el-radius-sm);
  cursor: pointer;
  transition: background var(--el-transition);
  user-select: none;
}
.el-checkbox-item:hover { background: var(--el-bg); }
.el-checkbox-item input[type="checkbox"] {
  width: 16px; height: 16px;
  accent-color: var(--el-primary);
  flex-shrink: 0;
  margin-top: 2px;
  cursor: pointer;
}
.el-checkbox-label {
  font-size: .85rem;
  color: var(--el-text);
  line-height: 1.4;
  flex: 1;
}
.el-checkbox-count {
  font-size: .75rem;
  color: var(--el-text-muted);
  margin-left: auto;
  flex-shrink: 0;
  background: var(--el-bg2);
  padding: 1px 7px;
  border-radius: 10px;
}

/* Collapsible groups */
.el-filter-group-toggle {
  background: none; border: none; cursor: pointer;
  display: flex; align-items: center; justify-content: space-between;
  width: 100%; padding: 0;
}
.el-filter-group-toggle:hover { background: none; }
.el-filter-group-toggle .toggle-arrow { transition: transform .2s; color: var(--el-text-muted); font-size: .8rem; }
.el-filter-group-toggle.collapsed .toggle-arrow { transform: rotate(-90deg); }
.el-filter-group-content { overflow: hidden; }
.el-filter-group-content.collapsed { display: none; }

/* Author/publisher search inside sidebar */
.el-sidebar-search {
  padding: 7px 11px;
  border: 1.5px solid var(--el-border);
  border-radius: 6px;
  font-size: .83rem;
  font-family: var(--el-font);
  width: 100%;
  margin-bottom: 10px;
  outline: none;
  transition: border-color .2s;
  color: var(--el-text);
}
.el-sidebar-search:focus { border-color: var(--el-primary); }

.el-sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--el-border);
  display: flex;
  gap: 10px;
  flex-shrink: 0;
}
.el-btn-clear-all {
  flex: 1;
  padding: 10px;
  background: none;
  border: 2px solid var(--el-border);
  border-radius: var(--el-radius-sm);
  font-size: .88rem;
  font-weight: 600;
  font-family: var(--el-font);
  color: var(--el-text-muted);
  cursor: pointer;
  transition: all var(--el-transition);
}
.el-btn-clear-all:hover { border-color: var(--el-primary); color: var(--el-primary); }
.el-btn-apply-filters {
  flex: 1;
  padding: 10px;
  background: var(--el-primary);
  border: 2px solid var(--el-primary);
  border-radius: var(--el-radius-sm);
  font-size: .88rem;
  font-weight: 700;
  font-family: var(--el-font);
  color: #fff;
  cursor: pointer;
  transition: all var(--el-transition);
}
.el-btn-apply-filters:hover { background: var(--el-primary-dark); }

/* ═══════════════════════════════════
   MAIN CONTENT LAYOUT
   ═══════════════════════════════════ */
.el-page-body {
  width: 85%;
  max-width: 1400px;
  margin: 0 auto;
  padding: 40px 0 60px;
}
@media (max-width: 900px) { .el-page-body { width: 95%; } }
@media (max-width: 600px) { .el-page-body { width: 100%; padding: 24px 0 40px; } }

/* ── No Results ── */
.el-no-results {
  text-align: center;
  padding: 80px 24px;
  color: var(--el-text-muted);
  display: none;
}
.el-no-results.visible { display: block; }
.el-no-results i { font-size: 2.8rem; color: var(--el-primary-mid); margin-bottom: 16px; display: block; }
.el-no-results p { font-size: 1.05rem; }

/* ═══════════════════════════════════
   TOPIC SECTIONS
   ═══════════════════════════════════ */
.el-topic-section {
  margin-bottom: 56px;
  scroll-margin-top: 24px;
}
.el-topic-section[data-hidden="true"] { display: none; }

.el-section-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--el-primary-mid);
}
.el-section-title-wrap {
  display: flex;
  align-items: flex-start;
  gap: 12px;
}
.el-section-dot {
  width: 10px; height: 10px;
  background: var(--el-primary);
  border-radius: 50%;
  flex-shrink: 0;
  margin-top: 7px; /* aligns top with first line of text */
}
.el-section-title {
  font-size: 1.4rem;
  font-weight: 800;
  color: var(--el-primary-dark);
  line-height: 1.3;
}
.el-section-count {
  background: var(--el-primary-light);
  color: var(--el-primary);
  font-size: .75rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 20px;
  white-space: nowrap;
  margin-top: 4px;
  flex-shrink: 0;
}

/* ═══════════════════════════════════
   BOOKS GRID
   ═══════════════════════════════════ */
.el-books-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

/* ── Book Card ── */
.el-book-card {
  border-radius: var(--el-radius);
  border: 1px solid var(--el-border);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform var(--el-transition), box-shadow var(--el-transition), border-color var(--el-transition);
}
.el-book-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--el-shadow-lg);
  border-color: var(--el-primary-mid);
}
.el-book-card.el-book-hidden { display: none; }
.el-book-card[data-filtered-out="true"] { display: none; }

.el-card-cover-wrap {
  position: relative;
  padding: 0 44px;
  background: var(--el-bg2);
  flex-shrink: 0;
  overflow: hidden;
}
.el-card-cover {
  width: 100%;
  aspect-ratio: 3/4;
  object-fit: cover;
  display: block;
  transition: transform .4s ease;
}
.el-book-card:hover .el-card-cover { transform: scale(1.04); }

.el-card-body {
  padding: 14px 16px 10px;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 7px;
}
.el-card-title {
  font-size: .92rem;
  font-weight: 700;
  color: var(--el-text);
  line-height: 1.45;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.el-card-meta {
  font-size: .78rem;
  color: var(--el-text-muted);
  display: flex;
  align-items: flex-start;
  gap: 7px;
  line-height: 1.4;
}
.el-card-meta i { display: none; }
.el-meta-label {
  font-weight: 600;
  color: var(--el-primary);
  font-size: .7rem;
  text-transform: uppercase;
  letter-spacing: .4px;
}

.el-card-actions {
  padding: 0 14px 14px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}
.el-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 9px 6px;
  border-radius: var(--el-radius-sm);
  font-size: .8rem;
  font-weight: 700;
  font-family: var(--el-font);
  text-decoration: none;
  transition: all var(--el-transition);
  border: 2px solid transparent;
  cursor: pointer;
}
.el-btn i { font-size: .8rem; }
.el-btn-preview {
  background: var(--el-primary-light);
  color: var(--el-primary);
  border-color: var(--el-primary-mid);
}
.el-btn-preview:hover {
  background: var(--el-primary);
  color: #fff;
  border-color: var(--el-primary);
}
.el-btn-download {
  background: var(--el-green-bg);
  color: var(--el-green);
  border-color: #a7f3d0;
}
.el-btn-download:hover {
  background: var(--el-green);
  color: #fff;
  border-color: var(--el-green);
}

/* ── See More ── */
.el-see-more-wrap { text-align: center; margin-top: 30px; }
.el-see-more-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 32px;
  background: var(--el-surface);
  border: 2px solid var(--el-primary);
  border-radius: 30px;
  color: var(--el-primary);
  font-size: .9rem;
  font-weight: 700;
  font-family: var(--el-font);
  cursor: pointer;
  transition: all var(--el-transition);
}
.el-see-more-btn:hover { background: var(--el-primary); color: #fff; }
.el-see-more-arrow { transition: transform var(--el-transition); font-size: .85rem; }
.el-see-more-btn.expanded .el-see-more-arrow { transform: rotate(180deg); }

/* ═══════════════════════════════════
   MOBILE  ≤ 600px
   ═══════════════════════════════════ */
@media (max-width: 600px) {
  .el-hero { padding: 48px 20px 40px; }
  .el-hero-title { font-size: 1.7rem; }
  .el-hero-icon { width: 58px; height: 58px; border-radius: 16px; }
  .el-hero-icon i { font-size: 1.4rem; }

  .el-page-body { padding: 20px 0 32px; }

  /* Single column, same vertical card layout as desktop */
  .el-books-grid {
    grid-template-columns: 1fr;
    gap: 18px;
    padding: 0 5%;
  }
  .el-book-card {
    flex-direction: column;
    border-radius: var(--el-radius);
  }
  .el-card-cover-wrap {
    padding: 0 80px ;
    aspect-ratio: unset;
    width: 100%;
  }
  .el-card-cover {
    width: 100%;
    aspect-ratio: 3/4;
  }

  .el-topic-section { margin-bottom: 36px; }
  .el-section-title { font-size: 1.15rem; }
  .el-section-header { padding: 0 5% 14px; }

  /* See more */
  .el-see-more-wrap { padding: 0 5%; }
  .el-see-more-btn { width: 100%; justify-content: center; }

  /* Filter sidebar full width on mobile */
  .el-filter-sidebar { width: 100%; right: -100%; }
  .el-filter-sidebar.open { right: 0; }
}

@media (min-width: 601px) and (max-width: 900px) {
  .el-books-grid { grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 18px; }
}

/* ═══════════════════════════════════
   SCROLLBAR
   ═══════════════════════════════════ */
.el-library-root ::-webkit-scrollbar { width: 6px; }
.el-library-root ::-webkit-scrollbar-track { background: var(--el-bg); }
.el-library-root ::-webkit-scrollbar-thumb { background: var(--el-primary-mid); border-radius: 4px; }