:root {
  --primary:        #1a56db;
  --primary-light:  #eff6ff;
  --primary-dark:   #1140a6;
  --accent:         #e74c3c;
  --surface:        #f8fafc;
  --card:           #ffffff;
  --border:         #e2e8f0;
  --text-main:      #1e293b;
  --text-muted:     #64748b;
  --text-faint:     #94a3b8;
  --radius-sm:      6px;
  --radius-md:      10px;
  --radius-lg:      14px;
  --shadow-sm:      0 1px 3px rgba(0,0,0,.07), 0 1px 2px rgba(0,0,0,.05);
  --shadow-md:      0 4px 12px rgba(0,0,0,.08), 0 2px 4px rgba(0,0,0,.05);
  --shadow-lg:      0 10px 30px rgba(0,0,0,.1);
  --transition:     0.2s ease;
}

/* ── Reset / base ──────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: 'IBM Plex Sans', sans-serif; background: var(--surface); }

/* Scrollbar hide utility */
.scrollbar-hide::-webkit-scrollbar { display: none; }
.scrollbar-hide { -ms-overflow-style: none; scrollbar-width: none; }

/* ── Header ────────────────────────────────────────────── */
.site-header {
  background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary) 60%, #2d74f0 100%);
  box-shadow: 0 2px 12px rgba(26,86,219,.35);
}

.header-icon {
  width: 44px; height: 44px;
  background: rgba(255,255,255,.15);
  border-radius: var(--radius-md);
  display: flex; align-items: center; justify-content: center;
  color: white;
  flex-shrink: 0;
}

/* ── Year tab bar ───────────────────────────────────────── */
.year-tab-bar {
  background: var(--card);
  border-bottom: 2px solid var(--border);
  box-shadow: var(--shadow-sm);
  position: sticky; top: 0; z-index: 20;
}

.year-tab {
  flex-shrink: 0;
  padding: 10px 16px;
  font-family: 'DM Sans', sans-serif;
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--text-muted);
  border-radius: var(--radius-sm) var(--radius-sm) 0 0;
  border: none;
  background: transparent;
  cursor: pointer;
  transition: color var(--transition), background var(--transition);
  white-space: nowrap;
  position: relative;
}

.year-tab::after {
  content: '';
  position: absolute;
  bottom: -2px; left: 0; right: 0;
  height: 2px;
  background: var(--primary);
  transform: scaleX(0);
  transition: transform var(--transition);
  border-radius: 2px 2px 0 0;
}

.year-tab:hover { color: var(--primary); background: var(--primary-light); }

.year-tab.active {
  color: var(--primary);
  background: var(--primary-light);
}
.year-tab.active::after { transform: scaleX(1); }

/* ── Sidebar ────────────────────────────────────────────── */
.sidebar {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 8px;
  box-shadow: var(--shadow-sm);
  align-self: flex-start;
  position: sticky;
  top: 64px;
}

.sidebar-item {
  display: block;
  width: 100%;
  text-align: left;
  padding: 10px 14px;
  font-family: 'DM Sans', sans-serif;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  border: none;
  background: transparent;
  cursor: pointer;
  transition: all var(--transition);
  line-height: 1.4;
  margin-bottom: 2px;
}

.sidebar-item:hover {
  background: var(--primary-light);
  color: var(--primary);
}

.sidebar-item.active {
  background: var(--primary);
  color: white;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(26,86,219,.3);
}

/* ── Content header ─────────────────────────────────────── */
.content-header h2 {
  font-family: 'DM Sans', sans-serif;
  position: relative;
  padding-left: 14px;
}
.content-header h2::before {
  content: '';
  position: absolute;
  left: 0; top: 2px; bottom: 2px;
  width: 4px;
  background: var(--primary);
  border-radius: 4px;
}

/* ── Accordion card ─────────────────────────────────────── */
.accordion-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition);
}
.accordion-card:hover { box-shadow: var(--shadow-md); }

.acc-header {
  background: transparent;
  border: none;
  cursor: pointer;
  transition: background var(--transition);
  border-bottom: 1px solid transparent;
}
.acc-header:hover { background: var(--primary-light); }

.acc-chevron { transition: transform 0.3s ease; }

/* ── Folder label ───────────────────────────────────────── */
.folder-label {
  background: var(--primary-light);
  border-radius: var(--radius-sm);
  padding: 8px 12px;
  font-family: 'DM Sans', sans-serif;
}

/* ── View controls ──────────────────────────────────────── */
.view-btn, .size-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 5px 10px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text-muted);
  cursor: pointer;
  font-family: 'DM Sans', sans-serif;
  font-size: 0.78rem;
  font-weight: 600;
  transition: all var(--transition);
}
.view-btn:hover, .size-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-light);
}
.view-btn.active, .size-btn.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

/* ── File Grid ──────────────────────────────────────────── */
.file-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(calc(var(--icon-size, 72px) + 52px), 1fr));
  gap: 14px;
}

.file-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 14px 10px 10px;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition);
  box-shadow: var(--shadow-sm);
}
.file-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--primary);
  transform: translateY(-2px);
  background: white;
}

.file-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 8px;
  filter: drop-shadow(0 2px 6px rgba(220,38,38,.15));
  transition: filter var(--transition);
}
.file-card:hover .file-icon {
  filter: drop-shadow(0 4px 10px rgba(220,38,38,.25));
}

.file-name {
  font-family: 'DM Sans', sans-serif;
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--text-main);
  word-break: break-word;
  line-height: 1.35;
  max-width: 100%;
  margin-bottom: 2px;
}

.file-size {
  font-size: 0.68rem;
  color: var(--text-faint);
  margin-bottom: 4px;
}

/* ── File List ──────────────────────────────────────────── */
.file-list { list-style: none; display: flex; flex-direction: column; gap: 6px; }

.file-list-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}
.file-list-item:hover {
  background: var(--card);
  border-color: var(--primary);
  box-shadow: var(--shadow-sm);
}

/* ── Download button ────────────────────────────────────── */
.dl-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  padding: 5px 12px;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: var(--radius-sm);
  font-family: 'DM Sans', sans-serif;
  font-size: 0.72rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
  flex-shrink: 0;
}
.dl-btn:hover {
  background: var(--primary-dark);
  box-shadow: 0 3px 10px rgba(26,86,219,.35);
  transform: translateY(-1px);
}
.dl-btn:active { transform: translateY(0); }

/* ── Animations ─────────────────────────────────────────── */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

.accordion-card {
  animation: fadeInUp 0.25s ease both;
}
.accordion-card:nth-child(2) { animation-delay: 0.05s; }
.accordion-card:nth-child(3) { animation-delay: 0.10s; }
.accordion-card:nth-child(4) { animation-delay: 0.15s; }

/* ── Responsive ─────────────────────────────────────────── */
@media (max-width: 768px) {
  #mainContent { flex-direction: column; }
  .sidebar {
    width: 100% !important;
    position: static;
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
  }
  .sidebar-item { flex: 1 0 auto; text-align: center; font-size: 0.72rem; }
}