/* ===================================================
   LeetCode Solutions Archive — Premium Dark Mode UI
   =================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

/* ── Reset & Variables ── */
:root {
  --bg:           #0d1117;
  --bg-card:      #161b22;
  --bg-hover:     #1c2128;
  --border:       #30363d;
  --border-subtle:#21262d;
  --text-primary: #e6edf3;
  --text-muted:   #8b949e;
  --text-link:    #58a6ff;
  --accent:       #FFA116;  /* LeetCode orange */
  --accent-glow:  rgba(255,161,22,0.15);

  --easy:         #00b8a9;
  --easy-bg:      rgba(0,184,169,0.12);
  --medium:       #ffc01e;
  --medium-bg:    rgba(255,192,30,0.12);
  --hard:         #ff375f;
  --hard-bg:      rgba(255,55,95,0.12);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.4);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 20px rgba(255,161,22,0.08);

  --transition: 0.2s ease;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}

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

/* ── Layout ── */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px 60px;
}

/* ── Header / Hero ── */
.hero {
  background: linear-gradient(135deg, #0d1117 0%, #161b22 50%, #0d1117 100%);
  border-bottom: 1px solid var(--border);
  padding: 40px 20px 30px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: 50%;
  transform: translateX(-50%);
  width: 600px;
  height: 300px;
  background: radial-gradient(ellipse, rgba(255,161,22,0.06) 0%, transparent 70%);
  pointer-events: none;
}

.hero-logo {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
}

.hero-logo svg {
  width: 42px;
  height: 42px;
  filter: drop-shadow(0 0 8px var(--accent));
}

.hero-title {
  font-size: clamp(1.6rem, 4vw, 2.4rem);
  font-weight: 800;
  background: linear-gradient(135deg, #FFA116 30%, #ffcc75 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.5px;
}

.hero-subtitle {
  color: var(--text-muted);
  font-size: 0.95rem;
  margin-top: 6px;
  margin-bottom: 20px;
}

.social-links {
  display: flex;
  justify-content: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.social-btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 7px 16px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 20px;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-primary);
  transition: var(--transition);
}

.social-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
  text-decoration: none;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(255,161,22,0.2);
}

.social-btn svg { width: 15px; height: 15px; fill: currentColor; }

/* ── Stats Cards ── */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 14px;
  margin: 28px 0;
}

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 18px 20px;
  text-align: center;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}

.stat-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  border-radius: var(--radius-md) var(--radius-md) 0 0;
}

.stat-card.total::before  { background: linear-gradient(90deg, #58a6ff, #79c0ff); }
.stat-card.easy-card::before   { background: linear-gradient(90deg, var(--easy), #00e0d0); }
.stat-card.medium-card::before { background: linear-gradient(90deg, var(--medium), #ffe066); }
.stat-card.hard-card::before   { background: linear-gradient(90deg, var(--hard), #ff6a8a); }

.stat-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: #444c56;
}

.stat-icon {
  font-size: 1.5rem;
  margin-bottom: 6px;
  display: block;
}

.stat-value {
  font-size: 2rem;
  font-weight: 800;
  line-height: 1;
  color: var(--text-primary);
}

.stat-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.8px;
  margin-top: 4px;
}

/* ── Controls Bar ── */
.controls-bar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(13, 17, 23, 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  padding: 12px 20px;
  margin: 0 -20px 20px;
}

.controls-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  gap: 10px;
  align-items: center;
  flex-wrap: wrap;
}

.search-wrapper {
  flex: 1;
  min-width: 180px;
  position: relative;
}

.search-wrapper svg {
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  width: 16px;
  height: 16px;
  fill: var(--text-muted);
  pointer-events: none;
}

.search-input {
  width: 100%;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: inherit;
  font-size: 0.88rem;
  padding: 9px 12px 9px 36px;
  outline: none;
  transition: var(--transition);
}

.search-input::placeholder { color: var(--text-muted); }
.search-input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-glow); }

.filter-row {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-muted);
  font-size: 0.82rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  transition: var(--transition);
}

.filter-btn:hover { color: var(--text-primary); border-color: #555; }
.filter-btn.active { font-weight: 600; }
.filter-btn.active.all    { border-color: #58a6ff; color: #58a6ff; background: rgba(88,166,255,0.1); }
.filter-btn.active.easy   { border-color: var(--easy); color: var(--easy); background: var(--easy-bg); }
.filter-btn.active.medium { border-color: var(--medium); color: var(--medium); background: var(--medium-bg); }
.filter-btn.active.hard   { border-color: var(--hard); color: var(--hard); background: var(--hard-bg); }

.result-count {
  margin-left: auto;
  font-size: 0.8rem;
  color: var(--text-muted);
  white-space: nowrap;
}

/* ── Table ── */
.table-wrapper {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.solutions-table {
  width: 100%;
  border-collapse: collapse;
  min-width: 560px;
  display: table;
}

.solutions-table th {
  background: var(--bg-hover);
  padding: 12px 16px;
  text-align: left;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.6px;
  border-bottom: 1px solid var(--border);
  user-select: none;
  white-space: nowrap;
  cursor: pointer;
  transition: var(--transition);
}

.solutions-table th:hover { color: var(--text-primary); }

.solutions-table th .sort-icon { margin-left: 4px; opacity: 0.4; }
.solutions-table th.sorted .sort-icon { opacity: 1; color: var(--accent); }

.solutions-table td {
  padding: 11px 16px;
  border-bottom: 1px solid var(--border-subtle);
  font-size: 0.88rem;
  vertical-align: middle;
}

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

.solutions-table tbody tr {
  transition: background var(--transition);
}

.solutions-table tbody tr:hover {
  background: var(--bg-hover);
}

/* ID cell */
.prob-id {
  font-weight: 600;
  color: var(--text-muted);
  font-size: 0.82rem;
  width: 60px;
}

/* Name cell */
.prob-name {
  font-weight: 500;
  color: var(--text-primary);
}

/* Difficulty badge */
.diff-badge {
  display: inline-block;
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.3px;
  white-space: nowrap;
}

.diff-easy   { background: var(--easy-bg);   color: var(--easy);   border: 1px solid rgba(0,184,169,0.3); }
.diff-medium { background: var(--medium-bg); color: var(--medium); border: 1px solid rgba(255,192,30,0.3); }
.diff-hard   { background: var(--hard-bg);   color: var(--hard);   border: 1px solid rgba(255,55,95,0.3); }
.diff-unknown { background: rgba(139,148,158,0.1); color: var(--text-muted); border: 1px solid var(--border); }

/* Language badge */
.lang-badge {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.73rem;
  font-weight: 600;
  background: rgba(88,166,255,0.1);
  color: #79c0ff;
  border: 1px solid rgba(88,166,255,0.2);
}

/* Action buttons */
.action-cell { display: flex; gap: 7px; align-items: center; }

.btn-action {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 5px 11px;
  border-radius: var(--radius-sm);
  font-size: 0.76rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  border: none;
  text-decoration: none;
  transition: var(--transition);
  white-space: nowrap;
}

.btn-problem {
  background: rgba(139,148,158,0.1);
  color: var(--text-muted);
  border: 1px solid var(--border);
}

.btn-problem:hover {
  background: rgba(139,148,158,0.2);
  color: var(--text-primary);
  text-decoration: none;
}

.btn-solution {
  background: rgba(255,161,22,0.15);
  color: var(--accent);
  border: 1px solid rgba(255,161,22,0.3);
}

.btn-solution:hover {
  background: rgba(255,161,22,0.25);
  text-decoration: none;
  box-shadow: 0 0 12px rgba(255,161,22,0.15);
}

.btn-action svg { width: 13px; height: 13px; fill: currentColor; flex-shrink: 0; }

/* ── Empty / Loading states ── */
.state-msg {
  text-align: center;
  padding: 48px 24px;
  color: var(--text-muted);
  font-size: 0.92rem;
}

.state-msg .icon { font-size: 2.5rem; margin-bottom: 12px; display: block; }

/* ── Footer ── */
.footer {
  text-align: center;
  padding: 32px 20px 16px;
  color: var(--text-muted);
  font-size: 0.8rem;
  border-top: 1px solid var(--border-subtle);
  margin-top: 40px;
}

.footer a { color: var(--accent); }
.footer a:hover { text-decoration: underline; }

/* ── Scroll to top button ── */
#scroll-top {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 40px;
  height: 40px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 50%;
  display: none;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
  z-index: 999;
  color: var(--text-muted);
}

#scroll-top:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

#scroll-top.visible { display: flex; }
#scroll-top svg { width: 18px; height: 18px; fill: currentColor; }

/* ── Responsive ── */
@media (max-width: 768px) {
  .hero { padding: 28px 16px 24px; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .controls-inner { gap: 8px; }
  .table-wrapper { overflow-x: auto; }
  .action-cell { flex-direction: column; gap: 5px; }
}

@media (max-width: 480px) {
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .filter-row { gap: 6px; }
  .filter-btn { padding: 6px 12px; font-size: 0.78rem; }
}