:root {
  --bg-color: #0d1117;
  --surface-color: #161b22;
  --surface-hover: #1f242c;
  --border-color: #30363d;
  --border-subtle: rgba(48, 54, 61, 0.6);
  --table-header-bg: rgba(0, 0, 0, 0.25);
  --text-main: #f0f6fc;
  --text-muted: #8b949e;
  --accent-color: #58a6ff;
  --accent-hover: #79b8ff;
  --accent-bg: rgba(56, 139, 253, 0.15);
  
  --dot-lc: #ffa116;
  --dot-cf: #318ce7;
  --dot-hr: #00ea64;
  --dot-cc: #f59e0b;

  --badge-lang-bg: #21262d;
  --badge-lang-text: #c9d1d9;
  --count-bg: rgba(255, 255, 255, 0.08);
  --card-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
  
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-full: 9999px;
  
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

[data-theme="light"] {
  --bg-color: #f6f8fa;
  --surface-color: #ffffff;
  --surface-hover: #f3f4f6;
  --border-color: #d0d7de;
  --border-subtle: #eaeef2;
  --table-header-bg: #f6f8fa;
  --text-main: #1f2328;
  --text-muted: #656d76;
  --accent-color: #0969da;
  --accent-hover: #0550ae;
  --accent-bg: rgba(9, 105, 218, 0.1);
  
  --badge-lang-bg: #eaeef2;
  --badge-lang-text: #24292f;
  --count-bg: rgba(0, 0, 0, 0.06);
  --card-shadow: 0 1px 3px rgba(31, 35, 40, 0.08), 0 6px 16px rgba(66, 74, 83, 0.06);
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.5;
  min-height: 100vh;
  padding: 1.5rem 1rem;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
}

/* Header */
.header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.header h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-main);
}

.subtitle {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-top: 0.25rem;
}

.subtitle a {
  color: var(--accent-color);
  text-decoration: none;
  font-weight: 500;
}

.subtitle a:hover {
  text-decoration: underline;
}

.header-links {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

/* Instant Theme Toggle Button */
.theme-toggle-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  background-color: var(--surface-color);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  cursor: pointer;
}

.theme-toggle-btn:hover {
  background-color: var(--surface-hover);
  border-color: #8b949e;
}

.theme-icon {
  display: none;
}

/* Instant icon display based on theme attribute */
[data-theme="dark"] .theme-icon.moon {
  display: block;
}

[data-theme="light"] .theme-icon.sun {
  display: block;
}

.github-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background-color: var(--surface-color);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.5rem 0.9rem;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
  text-decoration: none;
}

.github-btn:hover {
  background-color: var(--surface-hover);
  border-color: #8b949e;
}

/* Controls Card */
.controls-card {
  background-color: var(--surface-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.25rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--card-shadow);
}

.search-box-wrap {
  position: relative;
  display: flex;
  align-items: center;
  margin-bottom: 1rem;
}

.search-icon {
  position: absolute;
  left: 0.85rem;
  color: var(--text-muted);
  pointer-events: none;
}

#searchInput {
  width: 100%;
  padding: 0.75rem 2.25rem 0.75rem 2.6rem;
  font-size: 1rem;
  font-family: inherit;
  background-color: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-main);
}

#searchInput:focus {
  outline: none;
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px var(--accent-bg);
}

#searchInput::-webkit-search-cancel-button {
  display: none;
}

.clear-btn {
  position: absolute;
  right: 0.75rem;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.25rem;
  cursor: pointer;
  display: none;
  line-height: 1;
  padding: 0.25rem;
}

.clear-btn:hover {
  color: var(--text-main);
}

/* Filters Row */
.filters-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.filter-group {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.filter-label {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
}

.pill-group {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
}

.pill {
  background-color: var(--bg-color);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-full);
  font-size: 0.825rem;
  font-weight: 500;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
}

.pill:hover {
  background-color: var(--surface-hover);
  color: var(--text-main);
}

.pill.active {
  background-color: var(--accent-bg);
  border-color: var(--accent-color);
  color: var(--accent-color);
  font-weight: 600;
}

.pill .count {
  font-size: 0.725rem;
  background-color: var(--count-bg);
  padding: 0.05rem 0.4rem;
  border-radius: var(--radius-full);
}

.pill-platform-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
}

.dot-lc { background-color: var(--dot-lc); }
.dot-cf { background-color: var(--dot-cf); }
.dot-hr { background-color: var(--dot-hr); }
.dot-cc { background-color: var(--dot-cc); }

.select-input {
  background-color: var(--bg-color);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  font-family: inherit;
  cursor: pointer;
}

.select-input:focus {
  outline: none;
  border-color: var(--accent-color);
}

/* Subfilters Row */
.subfilters-row {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px dashed var(--border-color);
  flex-wrap: wrap;
}

.subfilters-row.hidden {
  display: none !important;
}

.subfilter-pill {
  font-size: 0.775rem;
  padding: 0.25rem 0.65rem;
}

/* Results summary */
.results-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
  padding: 0 0.25rem;
}

.results-count {
  font-size: 0.875rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* Problem Table */
.table-container {
  background-color: var(--surface-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow-x: auto;
  box-shadow: var(--card-shadow);
}

.problem-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.9rem;
}

.problem-table th {
  background-color: var(--table-header-bg);
  padding: 0.75rem 1rem;
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border-color);
  white-space: nowrap;
}

.problem-table td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-subtle);
  vertical-align: middle;
}

.problem-table tr:last-child td {
  border-bottom: none;
}

.problem-table tbody tr:hover {
  background-color: var(--surface-hover);
}

.col-num {
  width: 50px;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.8rem;
}

.col-title {
  min-width: 320px;
}

.platform-icon-wrap {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-right: 0.5rem;
  vertical-align: middle;
  flex-shrink: 0;
}

.platform-icon {
  display: inline-block;
  vertical-align: middle;
}

.problem-title-link {
  color: var(--text-main);
  text-decoration: none;
  font-weight: 500;
  display: inline-flex;
  align-items: center;
}

.problem-title-link:hover {
  color: var(--accent-color);
}

.problem-title-link:hover span {
  text-decoration: underline;
}

.problem-title-plain {
  color: var(--text-main);
  font-weight: 500;
  display: inline-flex;
  align-items: center;
}

.external-arrow {
  font-size: 0.75rem;
  opacity: 0.6;
  margin-left: 0.35rem;
  text-decoration: none !important;
}

.col-cat {
  color: var(--text-muted);
  font-size: 0.85rem;
  white-space: nowrap;
}

.col-lang {
  width: 90px;
  white-space: nowrap;
}

.lang-badge {
  display: inline-block;
  background: var(--badge-lang-bg);
  color: var(--badge-lang-text);
  font-size: 0.75rem;
  font-family: var(--font-mono);
  padding: 0.15rem 0.45rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
}

.col-links {
  width: 100px;
  text-align: right;
  white-space: nowrap;
}

.solution-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  color: var(--accent-color);
  font-size: 0.825rem;
  font-weight: 500;
  text-decoration: none;
  padding: 0.25rem 0.5rem;
  border-radius: var(--radius-sm);
  background: var(--accent-bg);
}

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

/* Empty & Loading States */
.empty-state, .loading-state {
  text-align: center;
  padding: 3.5rem 1.5rem;
  background-color: var(--surface-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  margin-top: 1rem;
}

.empty-state.hidden, .loading-state.hidden {
  display: none !important;
}

.empty-icon {
  font-size: 2.5rem;
  margin-bottom: 0.75rem;
}

.empty-state h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.empty-state p {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 1.25rem;
}

.reset-btn {
  background-color: var(--surface-hover);
  color: var(--text-main);
  border: 1px solid var(--border-color);
  padding: 0.45rem 1rem;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
}

.reset-btn:hover {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
  color: #fff;
}

.spinner {
  width: 32px;
  height: 32px;
  border: 3px solid var(--border-color);
  border-top-color: var(--accent-color);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin: 0 auto 1rem;
}

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

/* Responsive adjustments */
@media (max-width: 768px) {
  .header h1 {
    font-size: 1.6rem;
  }
  
  .controls-card {
    padding: 1rem;
  }
  
  .filters-row {
    flex-direction: column;
    align-items: stretch;
  }
  
  .filter-group {
    width: 100%;
    justify-content: flex-start;
  }
  
  .select-input {
    width: 100%;
  }
}