/* ============================================
   LeetCode Explorer — Premium Dark Design
   ============================================ */

:root {
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-card: rgba(255, 255, 255, 0.03);
  --bg-card-hover: rgba(255, 255, 255, 0.07);
  --bg-glass: rgba(255, 255, 255, 0.04);
  --border-glass: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(255, 255, 255, 0.15);

  --text-primary: #f0f0f5;
  --text-secondary: #8e8ea0;
  --text-muted: #5a5a6e;

  --accent: #6c5ce7;
  --accent-glow: rgba(108, 92, 231, 0.25);
  --accent-light: #a29bfe;

  --easy: #00b894;
  --easy-bg: rgba(0, 184, 148, 0.12);
  --medium: #fdcb6e;
  --medium-bg: rgba(253, 203, 110, 0.12);
  --hard: #e17055;
  --hard-bg: rgba(225, 112, 85, 0.12);

  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;

  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 40px rgba(108, 92, 231, 0.15);

  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-med: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);

  --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font);
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  line-height: 1.6;
}

/* ---- Ambient blobs ---- */
.bg-blob {
  position: fixed;
  border-radius: 50%;
  filter: blur(120px);
  pointer-events: none;
  z-index: 0;
  opacity: 0.4;
}
.bg-blob-1 {
  width: 600px; height: 600px;
  background: radial-gradient(circle, rgba(108,92,231,0.35), transparent 70%);
  top: -200px; left: -100px;
}
.bg-blob-2 {
  width: 500px; height: 500px;
  background: radial-gradient(circle, rgba(0,184,148,0.2), transparent 70%);
  top: 40%; right: -150px;
}
.bg-blob-3 {
  width: 400px; height: 400px;
  background: radial-gradient(circle, rgba(253,203,110,0.15), transparent 70%);
  bottom: -100px; left: 30%;
}

/* ---- Header ---- */
header {
  position: relative;
  z-index: 2;
  text-align: center;
  padding: 56px 24px 24px;
}
.header-inner {
  max-width: 800px;
  margin: 0 auto;
}
.logo {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  cursor: pointer;
  transition: transform var(--transition-fast);
}
.logo:hover { transform: scale(1.03); }
.logo-icon {
  font-size: 2.4rem;
  animation: pulse 2s infinite;
}
@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.15); }
}
.logo h1 {
  font-size: 2.2rem;
  font-weight: 800;
  letter-spacing: -1px;
  background: linear-gradient(135deg, var(--text-primary) 0%, var(--accent-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.accent { font-weight: 900; }
.subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-top: 8px;
  font-weight: 400;
}

/* ---- Search ---- */
#search-section {
  position: sticky;
  top: 0;
  z-index: 10;
  padding: 16px 24px 12px;
  background: rgba(10, 10, 15, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}
.search-container {
  max-width: 640px;
  margin: 0 auto;
  position: relative;
}
.search-icon {
  position: absolute;
  left: 18px; top: 50%;
  transform: translateY(-50%);
  width: 20px; height: 20px;
  color: var(--text-muted);
  pointer-events: none;
}
#search-input {
  width: 100%;
  padding: 14px 90px 14px 50px;
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-xl);
  background: var(--bg-glass);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: var(--font);
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
#search-input::placeholder { color: var(--text-muted); }
#search-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-glow);
}
.search-count {
  position: absolute;
  right: 18px; top: 50%;
  transform: translateY(-50%);
  font-size: 0.8rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* ---- Company Grid ---- */
#company-grid-view {
  position: relative;
  z-index: 1;
  padding: 24px;
  max-width: 1400px;
  margin: 0 auto;
}
.company-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
}
.company-card {
  position: relative;
  background: var(--bg-card);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  padding: 20px;
  cursor: pointer;
  transition: all var(--transition-med);
  overflow: hidden;
}
.company-card::before {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--accent-glow), transparent 60%);
  opacity: 0;
  transition: opacity var(--transition-med);
}
.company-card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-card), var(--shadow-glow);
}
.company-card:hover::before { opacity: 1; }
.company-card-content {
  position: relative;
  z-index: 1;
}
.company-name {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.company-meta {
  display: flex;
  align-items: center;
  gap: 8px;
}
.problem-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--accent-light);
  background: rgba(108,92,231,0.1);
  padding: 3px 10px;
  border-radius: 20px;
}
.company-initial {
  width: 40px; height: 40px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  font-weight: 700;
  color: #fff;
  margin-bottom: 12px;
  flex-shrink: 0;
}

/* ---- Company Detail View ---- */
#company-detail-view {
  position: relative;
  z-index: 1;
  padding: 24px;
  max-width: 1200px;
  margin: 0 auto;
}
#company-detail-view.hidden { display: none; }

.detail-header {
  margin-bottom: 24px;
}
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.88rem;
  padding: 8px 16px;
  cursor: pointer;
  font-family: var(--font);
  transition: all var(--transition-fast);
}
.back-btn svg { width: 16px; height: 16px; }
.back-btn:hover {
  color: var(--text-primary);
  border-color: var(--border-hover);
  background: var(--bg-card-hover);
}
.detail-title-row {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-top: 16px;
  flex-wrap: wrap;
}
#detail-company-name {
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, #fff, var(--accent-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.problem-count-badge {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-light);
  background: rgba(108,92,231,0.15);
  padding: 4px 14px;
  border-radius: 20px;
}

/* Tabs */
.tabs-wrapper {
  overflow-x: auto;
  margin-bottom: 16px;
  -webkit-overflow-scrolling: touch;
}
.tabs {
  display: flex;
  gap: 6px;
  padding: 4px;
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  width: fit-content;
  min-width: 100%;
}
.tab {
  flex: 1;
  padding: 10px 18px;
  border: none;
  border-radius: 10px;
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}
.tab:hover {
  color: var(--text-primary);
  background: rgba(255,255,255,0.04);
}
.tab.active {
  background: var(--accent);
  color: #fff;
  font-weight: 600;
  box-shadow: 0 2px 12px var(--accent-glow);
}

/* Filters row */
.filters-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.difficulty-filters {
  display: flex;
  gap: 6px;
}
.diff-filter {
  padding: 6px 16px;
  border: 1px solid var(--border-glass);
  border-radius: 20px;
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
}
.diff-filter:hover { border-color: var(--border-hover); color: var(--text-primary); }
.diff-filter.active { color: #fff; }
.diff-filter.active[data-diff="all"] { background: var(--accent); border-color: var(--accent); }
.diff-filter.active[data-diff="EASY"] { background: var(--easy); border-color: var(--easy); color: #000; }
.diff-filter.active[data-diff="MEDIUM"] { background: var(--medium); border-color: var(--medium); color: #000; }
.diff-filter.active[data-diff="HARD"] { background: var(--hard); border-color: var(--hard); }

.stats-bar {
  display: flex;
  gap: 12px;
  font-size: 0.82rem;
  font-weight: 500;
}
.stat { color: var(--text-muted); }
.stat.easy { color: var(--easy); }
.stat.medium { color: var(--medium); }
.stat.hard { color: var(--hard); }

/* Table */
.table-container {
  background: var(--bg-glass);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  overflow: hidden;
}
#problem-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.88rem;
}
#problem-table thead {
  background: rgba(255,255,255,0.03);
  position: sticky;
  top: 0;
  z-index: 2;
}
#problem-table th {
  padding: 14px 16px;
  text-align: left;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-bottom: 1px solid var(--border-glass);
  user-select: none;
}
.sortable {
  cursor: pointer;
  transition: color var(--transition-fast);
}
.sortable:hover { color: var(--accent-light); }
.sort-arrow { font-size: 0.7rem; margin-left: 4px; }

#problem-table td {
  padding: 12px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.03);
  vertical-align: middle;
}
#problem-table tbody tr {
  transition: background var(--transition-fast);
}
#problem-table tbody tr:hover {
  background: rgba(108, 92, 231, 0.06);
}

.th-num { width: 50px; text-align: center; }
.th-diff { width: 100px; }
.th-freq { width: 110px; }
.th-acc { width: 110px; }

td:first-child { text-align: center; color: var(--text-muted); font-weight: 500; }

/* Difficulty badges */
.diff-badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 6px;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}
.diff-badge.easy { background: var(--easy-bg); color: var(--easy); }
.diff-badge.medium { background: var(--medium-bg); color: var(--medium); }
.diff-badge.hard { background: var(--hard-bg); color: var(--hard); }

/* Problem title link */
.problem-link {
  color: var(--text-primary);
  text-decoration: none;
  font-weight: 500;
  transition: color var(--transition-fast);
}
.problem-link:hover { color: var(--accent-light); text-decoration: underline; }

/* Frequency bar */
.freq-cell {
  display: flex;
  align-items: center;
  gap: 8px;
}
.freq-bar-bg {
  width: 60px;
  height: 5px;
  border-radius: 3px;
  background: rgba(255,255,255,0.06);
  overflow: hidden;
}
.freq-bar-fill {
  height: 100%;
  border-radius: 3px;
  background: linear-gradient(90deg, var(--accent), var(--accent-light));
  transition: width var(--transition-med);
}

/* Topic pills */
.topic-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
}
.topic-pill {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.68rem;
  font-weight: 500;
  background: rgba(255,255,255,0.05);
  color: var(--text-secondary);
  white-space: nowrap;
}

/* Empty state */
.empty-state {
  text-align: center;
  padding: 60px 24px;
  color: var(--text-muted);
}
.empty-state.hidden { display: none; }
.empty-icon { font-size: 3rem; display: block; margin-bottom: 12px; }

/* Footer */
footer {
  text-align: center;
  padding: 40px 24px;
  color: var(--text-muted);
  font-size: 0.82rem;
  position: relative;
  z-index: 1;
}
footer a { color: var(--accent-light); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* ---- Animations ---- */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}
.fade-in-up {
  animation: fadeInUp var(--transition-slow) both;
}
.company-card { animation: fadeInUp 0.4s both; }

/* Stagger cards */
.company-card:nth-child(4n+1) { animation-delay: 0s; }
.company-card:nth-child(4n+2) { animation-delay: 0.03s; }
.company-card:nth-child(4n+3) { animation-delay: 0.06s; }
.company-card:nth-child(4n+4) { animation-delay: 0.09s; }

/* Acceptance */
.acc-val { font-variant-numeric: tabular-nums; }

/* ---- Loading skeleton ---- */
.skeleton-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 16px;
}
.skeleton-card {
  height: 90px;
  border-radius: var(--radius-md);
  background: linear-gradient(90deg, var(--bg-card) 25%, rgba(255,255,255,0.06) 50%, var(--bg-card) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
}
@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ---- Responsive ---- */
@media (max-width: 768px) {
  .logo h1 { font-size: 1.6rem; }
  .company-grid { grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 10px; }
  .company-card { padding: 14px; }
  #detail-company-name { font-size: 1.5rem; }
  .tabs { gap: 4px; }
  .tab { padding: 8px 12px; font-size: 0.78rem; }
  #problem-table { font-size: 0.8rem; }
  #problem-table th, #problem-table td { padding: 10px 10px; }
  .th-topics { display: none; }
  .td-topics { display: none; }
  .filters-row { flex-direction: column; align-items: flex-start; }
}

@media (max-width: 480px) {
  header { padding: 36px 16px 16px; }
  .company-grid { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); }
  .th-freq, .td-freq { display: none; }
}

/* Scrollbar */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: rgba(255,255,255,0.2); }