/* ---------- reset & base ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* ---------- theme variables ---------- */
:root {
  color-scheme: dark;
  --bg: #0a0e1a;
  --bg-secondary: #111827;
  --card: rgba(17, 24, 39, 0.8);
  --card-border: rgba(255, 255, 255, 0.06);
  --card-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
  --text: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #1e293b;
  --input-bg: rgba(15, 23, 42, 0.6);
  --input-border: #334155;
  --input-focus: #6366f1;
  --accent: #6366f1;
  --accent-hover: #4f46e5;
  --accent-glow: rgba(99, 102, 241, 0.2);
  --link: #818cf8;
  --table-header: #1e1b4b;
  --table-row-even: rgba(255, 255, 255, 0.02);
  --table-row-hover: rgba(99, 102, 241, 0.06);
  --table-border: rgba(255, 255, 255, 0.05);
  --error-bg: rgba(239, 68, 68, 0.1);
  --error-text: #fca5a5;
  --error-border: rgba(239, 68, 68, 0.2);
  --toolbar-btn-bg: rgba(30, 41, 59, 0.8);
  --toolbar-btn-border: #334155;
  --toolbar-btn-text: #e2e8f0;
  --toolbar-btn-hover: rgba(99, 102, 241, 0.1);
  --note-bg: rgba(234, 179, 8, 0.06);
  --note-border: rgba(234, 179, 8, 0.2);
  --note-text: #fbbf24;
  --stats-bg: rgba(17, 24, 39, 0.8);
  --stats-border: rgba(255, 255, 255, 0.06);
  --success: #10b981;
  --toast-bg: rgba(17, 24, 39, 0.95);
}

.light {
  color-scheme: light;
  --bg: #f8fafc;
  --bg-secondary: #f1f5f9;
  --card: rgba(255, 255, 255, 0.9);
  --card-border: rgba(0, 0, 0, 0.06);
  --card-shadow: 0 8px 32px rgba(0, 0, 0, 0.08);
  --text: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --input-bg: #ffffff;
  --input-border: #d1d5db;
  --input-focus: #6366f1;
  --accent: #6366f1;
  --accent-hover: #4f46e5;
  --accent-glow: rgba(99, 102, 241, 0.12);
  --link: #4f46e5;
  --table-header: #1e1b4b;
  --table-row-even: rgba(0, 0, 0, 0.015);
  --table-row-hover: rgba(99, 102, 241, 0.04);
  --table-border: #f1f5f9;
  --error-bg: rgba(239, 68, 68, 0.06);
  --error-text: #dc2626;
  --error-border: rgba(239, 68, 68, 0.15);
  --toolbar-btn-bg: #ffffff;
  --toolbar-btn-border: #e2e8f0;
  --toolbar-btn-text: #374151;
  --toolbar-btn-hover: rgba(99, 102, 241, 0.06);
  --note-bg: rgba(234, 179, 8, 0.06);
  --note-border: rgba(234, 179, 8, 0.2);
  --note-text: #92400e;
  --stats-bg: rgba(255, 255, 255, 0.9);
  --stats-border: rgba(0, 0, 0, 0.06);
  --success: #059669;
  --toast-bg: rgba(255, 255, 255, 0.95);
}

/* ---------- body ---------- */
body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  transition: background 0.4s ease, color 0.3s ease;
  overflow-x: hidden;
  position: relative;
}

/* ---------- background decoration ---------- */
.bg-decoration {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  overflow: hidden;
}

.blob {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.15;
  animation: blobFloat 20s ease-in-out infinite;
}

.light .blob { opacity: 0.08; }

.blob-1 {
  width: 600px;
  height: 600px;
  background: #6366f1;
  top: -200px;
  right: -100px;
}

.blob-2 {
  width: 400px;
  height: 400px;
  background: #ec4899;
  bottom: -100px;
  left: -100px;
  animation-delay: -7s;
}

.blob-3 {
  width: 300px;
  height: 300px;
  background: #06b6d4;
  top: 50%;
  left: 50%;
  animation-delay: -14s;
}

@keyframes blobFloat {
  0%, 100% { transform: translate(0, 0) scale(1); }
  33% { transform: translate(30px, -20px) scale(1.05); }
  66% { transform: translate(-20px, 20px) scale(0.95); }
}

/* ---------- container ---------- */
.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 40px 24px 60px;
  position: relative;
  z-index: 1;
}

/* ---------- header ---------- */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 36px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 14px;
}

.logo-icon {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, var(--accent), #a855f7);
  border-radius: 14px;
  color: #fff;
  flex-shrink: 0;
}

.logo-text h1 {
  font-size: 1.5rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--text), var(--text-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.tagline {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-top: 2px;
}

/* ---------- theme toggle ---------- */
.theme-toggle {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--card);
  border: 1px solid var(--card-border);
  color: var(--text-secondary);
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.2s ease;
  backdrop-filter: blur(12px);
}

.theme-toggle:hover {
  background: var(--toolbar-btn-hover);
  color: var(--accent);
  border-color: var(--accent);
  transform: scale(1.05);
}

.icon-moon { display: none; }
.light .icon-sun { display: none; }
.light .icon-moon { display: block; }

/* ---------- form card ---------- */
.form-card {
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 20px;
  padding: 32px;
  box-shadow: var(--card-shadow);
  margin-bottom: 28px;
  backdrop-filter: blur(12px);
  animation: slideUp 0.5s ease;
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

.form-section {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 20px;
}

.form-group {
  display: flex;
  flex-direction: column;
}

.form-group label {
  font-weight: 500;
  margin-bottom: 8px;
  font-size: 0.82rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  display: flex;
  align-items: center;
  gap: 6px;
}

.form-group label svg {
  opacity: 0.6;
}

.form-group input,
.form-group select {
  padding: 12px 16px;
  border: 1px solid var(--input-border);
  border-radius: 12px;
  font-size: 0.92rem;
  font-family: inherit;
  transition: all 0.2s ease;
  background: var(--input-bg);
  color: var(--text);
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--input-focus);
  box-shadow: 0 0 0 4px var(--accent-glow);
}

.form-group input::placeholder {
  color: var(--text-muted);
}

/* ---------- platform buttons ---------- */
.platform-select {
  display: flex;
  gap: 8px;
}

.platform-btn {
  flex: 1;
  padding: 10px 12px;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 10px;
  color: var(--text-secondary);
  font-size: 0.82rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
}

.platform-btn:hover {
  border-color: var(--text-muted);
  color: var(--text);
}

.platform-btn.active {
  background: var(--accent-glow);
  border-color: var(--accent);
  color: var(--accent);
  font-weight: 600;
}

.light .platform-btn.active {
  background: rgba(99, 102, 241, 0.08);
}

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

.platform-dot.lc { background: #f59e0b; }
.platform-dot.cf { background: #3b82f6; }
.platform-dot.ac { background: #10b981; }

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

/* ---------- info note ---------- */
.info-note {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  background: var(--note-bg);
  border: 1px solid var(--note-border);
  color: var(--note-text);
  border-radius: 12px;
  padding: 12px 16px;
  margin-bottom: 20px;
  font-size: 0.82rem;
  line-height: 1.5;
}

.info-note svg {
  flex-shrink: 0;
  margin-top: 1px;
}

/* ---------- primary button ---------- */
.btn-primary {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  width: 100%;
  padding: 14px 20px;
  background: linear-gradient(135deg, var(--accent), #7c3aed);
  color: #fff;
  border: none;
  border-radius: 12px;
  font-size: 0.95rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
  overflow: hidden;
}

.btn-primary::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.1), transparent);
  opacity: 0;
  transition: opacity 0.2s;
}

.btn-primary:hover::before { opacity: 1; }
.btn-primary:hover { transform: translateY(-1px); box-shadow: 0 8px 24px var(--accent-glow); }
.btn-primary:active { transform: translateY(0); }
.btn-primary:disabled { opacity: 0.5; cursor: not-allowed; transform: none; box-shadow: none; }

/* ---------- loader ---------- */
.loader {
  text-align: center;
  padding: 40px 0;
  color: var(--text-secondary);
  font-size: 0.9rem;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin: 0 auto 14px;
}

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

/* ---------- error ---------- */
.error-box {
  display: flex;
  align-items: center;
  gap: 10px;
  background: var(--error-bg);
  color: var(--error-text);
  border: 1px solid var(--error-border);
  border-radius: 12px;
  padding: 14px 18px;
  margin-bottom: 20px;
  font-size: 0.88rem;
  animation: shakeIn 0.4s ease;
}

@keyframes shakeIn {
  0% { transform: translateX(-8px); opacity: 0; }
  50% { transform: translateX(4px); }
  100% { transform: translateX(0); opacity: 1; }
}

/* ---------- stats bar ---------- */
.stats-bar {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px;
  margin-bottom: 20px;
  animation: slideUp 0.4s ease;
}

.stat-card {
  background: var(--stats-bg);
  border: 1px solid var(--stats-border);
  border-radius: 14px;
  padding: 16px 18px;
  text-align: center;
  backdrop-filter: blur(12px);
  transition: transform 0.2s ease;
}

.stat-card:hover { transform: translateY(-2px); }

.stat-card .stat-value {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 2px;
}

.stat-card .stat-label {
  font-size: 0.72rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

.stat-total .stat-value { color: var(--accent); }
.stat-easy .stat-value { color: #10b981; }
.stat-medium .stat-value { color: #f59e0b; }
.stat-hard .stat-value { color: #ef4444; }

/* ---------- toolbar ---------- */
.toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 16px;
}

#resultCount {
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.toolbar-buttons { display: flex; gap: 8px; }

.btn-tool {
  padding: 8px 14px;
  background: var(--toolbar-btn-bg);
  border: 1px solid var(--toolbar-btn-border);
  color: var(--toolbar-btn-text);
  border-radius: 10px;
  font-size: 0.82rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.2s ease;
  backdrop-filter: blur(8px);
}

.btn-tool:hover {
  background: var(--toolbar-btn-hover);
  border-color: var(--accent);
  color: var(--accent);
}

/* ---------- table ---------- */
.table-wrap {
  overflow-x: auto;
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 16px;
  box-shadow: var(--card-shadow);
  backdrop-filter: blur(12px);
  animation: slideUp 0.5s ease;
}

table {
  width: 100%;
  border-collapse: collapse;
  min-width: 750px;
  font-size: 0.85rem;
}

thead th {
  background: var(--table-header);
  color: #e0e7ff;
  text-align: left;
  padding: 14px 16px;
  font-weight: 600;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  white-space: nowrap;
  position: sticky;
  top: 0;
  z-index: 1;
}

thead th:first-child { border-radius: 16px 0 0 0; }
thead th:last-child { border-radius: 0 16px 0 0; }

tbody td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--table-border);
  vertical-align: middle;
}

tbody tr { transition: background 0.15s ease; }
tbody tr:nth-child(even) { background: var(--table-row-even); }
tbody tr:hover { background: var(--table-row-hover); }
tbody tr:last-child td { border-bottom: none; }

td a {
  color: var(--link);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}

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

/* ---------- badges ---------- */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 10px;
  border-radius: 6px;
  font-size: 0.72rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.badge-easy { background: rgba(16, 185, 129, 0.12); color: #10b981; }
.badge-medium { background: rgba(245, 158, 11, 0.12); color: #f59e0b; }
.badge-hard { background: rgba(239, 68, 68, 0.12); color: #ef4444; }
.badge-unknown { background: rgba(148, 163, 184, 0.12); color: #94a3b8; }

.light .badge-easy { background: rgba(16, 185, 129, 0.08); color: #059669; }
.light .badge-medium { background: rgba(245, 158, 11, 0.08); color: #d97706; }
.light .badge-hard { background: rgba(239, 68, 68, 0.08); color: #dc2626; }

/* ---------- platform tag ---------- */
.platform-tag {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 0.8rem;
  font-weight: 500;
}

.platform-tag::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
}

.platform-tag.tag-leetcode::before { background: #f59e0b; }
.platform-tag.tag-codeforces::before { background: #3b82f6; }
.platform-tag.tag-atcoder::before { background: #10b981; }

/* ---------- toast ---------- */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: var(--toast-bg);
  border: 1px solid var(--card-border);
  color: var(--text);
  padding: 12px 24px;
  border-radius: 12px;
  font-size: 0.85rem;
  font-weight: 500;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
  backdrop-filter: blur(16px);
  z-index: 1000;
  opacity: 0;
  transition: all 0.3s ease;
}

.toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* ---------- footer ---------- */
.app-footer {
  text-align: center;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.78rem;
}

/* ---------- utility ---------- */
.hidden { display: none !important; }

/* ---------- responsive ---------- */
@media (max-width: 640px) {
  .container { padding: 24px 16px 40px; }
  .app-header { flex-wrap: wrap; gap: 12px; }
  .logo-text h1 { font-size: 1.2rem; }
  .form-card { padding: 24px 20px; border-radius: 16px; }
  .form-section { grid-template-columns: 1fr; gap: 16px; }
  .platform-select { flex-direction: column; }
  .toolbar { flex-direction: column; align-items: flex-start; }
  .toolbar-buttons { flex-wrap: wrap; }
  .stats-bar { grid-template-columns: repeat(2, 1fr); }
  .blob-1 { width: 300px; height: 300px; }
  .blob-2 { width: 200px; height: 200px; }
  .blob-3 { display: none; }
}