/* ============================================================
   LEETCODE RECOMMENDER — styles.css
   Theme: Neon Yellow × Jet Black × Glassmorphism
   ============================================================ */

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

/* ── CSS Variables ────────────────────────────────────────── */
:root {
  --neon:      #e8ff00;
  --neon-dim:  #b8cc00;
  --neon-glow: rgba(232,255,0,0.25);
  --neon-soft: rgba(232,255,0,0.08);
  --black:     #050505;
  --surface:   #0d0d0d;
  --card:      rgba(18,18,18,0.85);
  --border:    rgba(232,255,0,0.15);
  --border-hi: rgba(232,255,0,0.45);
  --muted:     #555;
  --text:      #d0d0d0;
  --white:     #f0f0f0;
  --easy:      #00e676;
  --medium:    #ffa726;
  --hard:      #ef5350;
  --radius:    12px;
  --radius-lg: 20px;
  --font-mono: 'JetBrains Mono', monospace;
  --font-body: 'Space Grotesk', sans-serif;
  --font-disp: 'Syne', sans-serif;
  --transition: 0.28s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ── Reset ────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; font-size: 16px; }

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

/* ── Scrollbar ────────────────────────────────────────────── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--black); }
::-webkit-scrollbar-thumb { background: var(--neon-dim); border-radius: 3px; }

/* ── Background mesh ──────────────────────────────────────── */
#bg-canvas {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  opacity: 0.35;
}

/* ── Noise overlay ────────────────────────────────────────── */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  z-index: 1;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='0.04'/%3E%3C/svg%3E");
  pointer-events: none;
  opacity: 0.4;
}

/* ── Layout wrapper ───────────────────────────────────────── */
.app { position: relative; z-index: 2; }

/* ── Navbar ───────────────────────────────────────────────── */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 2rem;
  height: 64px;
  background: rgba(5,5,5,0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  transition: var(--transition);
}
.navbar.scrolled {
  border-bottom-color: var(--border-hi);
  box-shadow: 0 4px 40px rgba(232,255,0,0.08);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  font-family: var(--font-disp);
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--neon);
  letter-spacing: -0.03em;
}
.nav-logo .logo-icon {
  width: 36px;
  height: 36px;
  background: var(--neon);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  color: var(--black);
  box-shadow: 0 0 16px var(--neon-glow);
  animation: logoPulse 3s ease-in-out infinite;
}
@keyframes logoPulse {
  0%,100% { box-shadow: 0 0 16px var(--neon-glow); }
  50%      { box-shadow: 0 0 32px rgba(232,255,0,0.5); }
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  list-style: none;
}
.nav-links a {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 8px;
  text-decoration: none;
  color: var(--text);
  font-size: 0.875rem;
  font-weight: 500;
  transition: var(--transition);
  position: relative;
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--neon);
  background: var(--neon-soft);
}
.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 50%;
  transform: translateX(-50%);
  width: 20px;
  height: 2px;
  background: var(--neon);
  border-radius: 2px;
}

.nav-hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 8px;
  border-radius: 8px;
  transition: var(--transition);
}
.nav-hamburger:hover { background: var(--neon-soft); }
.nav-hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--neon);
  border-radius: 2px;
  transition: var(--transition);
}

/* ── Section tabs ─────────────────────────────────────────── */
.section { display: none; padding: 2rem 2rem 4rem; max-width: 1400px; margin: 0 auto; }
.section.active { display: block; }

/* ── Page Header ──────────────────────────────────────────── */
.page-header {
  text-align: center;
  margin-bottom: 3rem;
  padding-top: 1rem;
}
.page-header .eyebrow {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.2em;
  color: var(--neon);
  text-transform: uppercase;
  margin-bottom: 0.75rem;
  opacity: 0;
}
.page-header h1 {
  font-family: var(--font-disp);
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 800;
  color: var(--white);
  line-height: 1.1;
  letter-spacing: -0.03em;
  opacity: 0;
  transform: translateY(20px);
}
.page-header h1 span { color: var(--neon); }
.page-header p {
  font-size: 1rem;
  color: var(--muted);
  margin-top: 0.75rem;
  max-width: 500px;
  margin-inline: auto;
  opacity: 0;
}

/* ── Stats grid ───────────────────────────────────────────── */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1rem;
  margin-bottom: 2.5rem;
}

.stat-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  text-align: center;
  backdrop-filter: blur(10px);
  transition: var(--transition);
  opacity: 0;
  transform: translateY(30px);
  cursor: default;
  position: relative;
  overflow: hidden;
}
.stat-card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, var(--neon-soft) 0%, transparent 60%);
  opacity: 0;
  transition: var(--transition);
}
.stat-card:hover {
  border-color: var(--border-hi);
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(232,255,0,0.12);
}
.stat-card:hover::before { opacity: 1; }

.stat-icon {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
  display: block;
  filter: drop-shadow(0 0 8px var(--neon-glow));
}
.stat-value {
  font-family: var(--font-mono);
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--neon);
  display: block;
  line-height: 1;
}
.stat-label {
  font-size: 0.75rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-top: 0.25rem;
  display: block;
}

/* ── Top tabs ─────────────────────────────────────────────── */
.tabs-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 1.5rem;
}
.tab-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--muted);
  padding: 7px 16px;
  border-radius: 8px;
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}
.tab-btn:hover {
  color: var(--white);
  border-color: var(--muted);
}
.tab-btn.active {
  background: var(--neon);
  border-color: var(--neon);
  color: var(--black);
  font-weight: 700;
}

/* ── Problem cards ────────────────────────────────────────── */
.problems-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1rem;
}

.problem-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  backdrop-filter: blur(12px);
  transition: var(--transition);
  opacity: 0;
  transform: translateY(20px);
  cursor: pointer;
  position: relative;
  overflow: hidden;
  text-decoration: none;
  display: block;
}
.problem-card::after {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg, var(--neon-soft), transparent 50%);
  opacity: 0;
  transition: var(--transition);
}
.problem-card:hover {
  border-color: var(--border-hi);
  transform: translateY(-6px);
  box-shadow: 0 20px 60px rgba(232,255,0,0.12);
}
.problem-card:hover::after { opacity: 1; }

.card-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
  position: relative;
  z-index: 1;
}
.card-num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--muted);
  padding: 2px 8px;
  background: rgba(255,255,255,0.05);
  border-radius: 4px;
  white-space: nowrap;
}
.card-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--white);
  line-height: 1.4;
  flex: 1;
  transition: var(--transition);
}
.problem-card:hover .card-title { color: var(--neon); }

.difficulty-badge {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 20px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  white-space: nowrap;
}
.difficulty-badge.Easy   { background: rgba(0,230,118,0.12); color: var(--easy);   border: 1px solid rgba(0,230,118,0.3); }
.difficulty-badge.Medium { background: rgba(255,167,38,0.12); color: var(--medium); border: 1px solid rgba(255,167,38,0.3); }
.difficulty-badge.Hard   { background: rgba(239,83,80,0.12);  color: var(--hard);   border: 1px solid rgba(239,83,80,0.3); }

.card-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
  font-size: 0.78rem;
  color: var(--muted);
  margin-bottom: 0.75rem;
  position: relative;
  z-index: 1;
}
.card-meta span { display: flex; align-items: center; gap: 4px; }

.card-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  position: relative;
  z-index: 1;
}
.tag {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  padding: 2px 9px;
  background: rgba(232,255,0,0.06);
  border: 1px solid rgba(232,255,0,0.12);
  color: var(--neon-dim);
  border-radius: 4px;
  transition: var(--transition);
}
.problem-card:hover .tag {
  background: rgba(232,255,0,0.1);
  border-color: rgba(232,255,0,0.25);
}

.faang-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.68rem;
  font-family: var(--font-mono);
  color: var(--neon);
  background: var(--neon-soft);
  border: 1px solid var(--border-hi);
  padding: 2px 8px;
  border-radius: 4px;
}

/* ── Search & filters ─────────────────────────────────────── */
.search-bar-wrap {
  position: relative;
  max-width: 640px;
  margin: 0 auto 1.5rem;
}
.search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--muted);
  font-size: 1rem;
  pointer-events: none;
}
.search-input {
  width: 100%;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 50px;
  padding: 14px 20px 14px 46px;
  font-family: var(--font-body);
  font-size: 0.95rem;
  color: var(--white);
  outline: none;
  transition: var(--transition);
  backdrop-filter: blur(10px);
}
.search-input::placeholder { color: var(--muted); }
.search-input:focus {
  border-color: var(--neon);
  box-shadow: 0 0 0 3px var(--neon-glow);
}

.autocomplete-dropdown {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  right: 0;
  background: rgba(15,15,15,0.97);
  border: 1px solid var(--border-hi);
  border-radius: var(--radius);
  backdrop-filter: blur(20px);
  z-index: 200;
  max-height: 260px;
  overflow-y: auto;
  box-shadow: 0 20px 60px rgba(0,0,0,0.7);
  display: none;
}
.autocomplete-dropdown.show { display: block; }
.autocomplete-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 16px;
  cursor: pointer;
  transition: var(--transition);
  font-size: 0.875rem;
}
.autocomplete-item:hover {
  background: var(--neon-soft);
  color: var(--neon);
}
.autocomplete-item .ac-title { flex: 1; }
.autocomplete-item .ac-diff { font-family: var(--font-mono); font-size: 0.7rem; }

.filters-row {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-bottom: 1.5rem;
  align-items: center;
}
.filter-select {
  background: var(--card);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 8px 14px;
  border-radius: 8px;
  font-family: var(--font-body);
  font-size: 0.85rem;
  outline: none;
  cursor: pointer;
  transition: var(--transition);
  backdrop-filter: blur(10px);
}
.filter-select:focus { border-color: var(--neon); }

.filter-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 14px;
  cursor: pointer;
  font-size: 0.85rem;
  color: var(--muted);
  transition: var(--transition);
  backdrop-filter: blur(10px);
  user-select: none;
}
.filter-toggle.active {
  border-color: var(--neon);
  color: var(--neon);
  background: var(--neon-soft);
}
.filter-toggle input { display: none; }

/* ── Pagination ───────────────────────────────────────────── */
.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 2.5rem;
  flex-wrap: wrap;
}
.page-btn {
  background: var(--card);
  border: 1px solid var(--border);
  color: var(--text);
  width: 38px;
  height: 38px;
  border-radius: 8px;
  cursor: pointer;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
  backdrop-filter: blur(10px);
}
.page-btn:hover:not(:disabled) {
  border-color: var(--neon);
  color: var(--neon);
}
.page-btn.active {
  background: var(--neon);
  border-color: var(--neon);
  color: var(--black);
  font-weight: 700;
}
.page-btn:disabled {
  opacity: 0.3;
  cursor: default;
}
.page-info {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--muted);
  padding: 0 0.75rem;
}

/* ── Recommend section ────────────────────────────────────── */
.recommend-search-wrap {
  max-width: 600px;
  margin: 0 auto 2rem;
  text-align: center;
}
.recommend-search-wrap h2 {
  font-family: var(--font-disp);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--white);
  margin-bottom: 1rem;
}
.recommend-search-wrap h2 span { color: var(--neon); }

.rec-source-card {
  background: linear-gradient(135deg, rgba(232,255,0,0.08), rgba(232,255,0,0.02));
  border: 1px solid var(--border-hi);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  margin-bottom: 2rem;
  text-align: center;
}
.rec-source-card .source-label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--neon);
  margin-bottom: 0.5rem;
}
.rec-source-card .source-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--white);
}

.recs-header {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--muted);
  margin-bottom: 1rem;
  padding-left: 4px;
}

.rec-card {
  display: flex;
  align-items: center;
  gap: 1rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.25rem;
  margin-bottom: 0.75rem;
  transition: var(--transition);
  opacity: 0;
  transform: translateX(-20px);
  cursor: pointer;
  backdrop-filter: blur(10px);
}
.rec-card:hover {
  border-color: var(--border-hi);
  transform: translateX(0) scale(1.01);
  box-shadow: 0 8px 30px rgba(232,255,0,0.1);
}
.rec-rank {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--neon);
  width: 28px;
  text-align: center;
  flex-shrink: 0;
}
.rec-body { flex: 1; min-width: 0; }
.rec-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--white);
  margin-bottom: 0.3rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.rec-meta { display: flex; align-items: center; gap: 0.75rem; font-size: 0.75rem; color: var(--muted); }
.sim-score {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--neon-dim);
  background: var(--neon-soft);
  border: 1px solid var(--border);
  padding: 2px 8px;
  border-radius: 4px;
  flex-shrink: 0;
}

/* ── Modal ────────────────────────────────────────────────── */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 1000;
  background: rgba(5,5,5,0.85);
  backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s;
}
.modal-overlay.show { opacity: 1; pointer-events: all; }

.modal {
  background: #0e0e0e;
  border: 1px solid var(--border-hi);
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 740px;
  max-height: 88vh;
  overflow-y: auto;
  padding: 2rem;
  position: relative;
  transform: scale(0.92) translateY(20px);
  transition: transform 0.35s cubic-bezier(0.34,1.56,0.64,1);
  box-shadow: 0 40px 100px rgba(0,0,0,0.8), 0 0 60px rgba(232,255,0,0.08);
}
.modal-overlay.show .modal { transform: scale(1) translateY(0); }

.modal-close {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--border);
  color: var(--muted);
  width: 32px;
  height: 32px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1rem;
  transition: var(--transition);
}
.modal-close:hover { background: var(--neon-soft); color: var(--neon); border-color: var(--neon); }

.modal-title {
  font-family: var(--font-disp);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--white);
  margin-bottom: 0.5rem;
  padding-right: 2.5rem;
  line-height: 1.3;
}
.modal-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
  margin-bottom: 1.25rem;
}
.modal-desc {
  font-size: 0.875rem;
  color: var(--text);
  line-height: 1.7;
  background: rgba(255,255,255,0.02);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1.25rem;
  margin-bottom: 1.25rem;
  max-height: 200px;
  overflow-y: auto;
  font-family: var(--font-mono);
  white-space: pre-wrap;
  word-break: break-word;
}
.modal-section-title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--neon);
  margin-bottom: 0.6rem;
}
.modal-tags { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 1.25rem; }
.modal-companies { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 1.5rem; }
.company-chip {
  font-size: 0.75rem;
  padding: 3px 10px;
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 5px;
  color: var(--text);
  transition: var(--transition);
}
.company-chip:hover {
  background: var(--neon-soft);
  border-color: var(--border-hi);
  color: var(--neon);
}
.modal-actions { display: flex; gap: 0.75rem; flex-wrap: wrap; }
.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  background: var(--neon);
  color: var(--black);
  border: none;
  border-radius: 8px;
  font-family: var(--font-body);
  font-weight: 700;
  font-size: 0.875rem;
  cursor: pointer;
  text-decoration: none;
  transition: var(--transition);
  box-shadow: 0 4px 20px rgba(232,255,0,0.3);
}
.btn-primary:hover {
  background: var(--white);
  box-shadow: 0 8px 30px rgba(232,255,0,0.4);
  transform: translateY(-2px);
}
.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  background: transparent;
  color: var(--neon);
  border: 1px solid var(--neon);
  border-radius: 8px;
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.875rem;
  cursor: pointer;
  text-decoration: none;
  transition: var(--transition);
}
.btn-secondary:hover {
  background: var(--neon-soft);
  box-shadow: 0 4px 20px rgba(232,255,0,0.15);
  transform: translateY(-2px);
}

/* ── Toaster ──────────────────────────────────────────────── */
#toaster {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 2000;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  pointer-events: none;
}
.toast {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 18px;
  background: rgba(15,15,15,0.96);
  border: 1px solid var(--border-hi);
  border-radius: 10px;
  backdrop-filter: blur(20px);
  box-shadow: 0 8px 32px rgba(0,0,0,0.6);
  font-size: 0.875rem;
  color: var(--white);
  pointer-events: all;
  transform: translateX(120%);
  transition: transform 0.4s cubic-bezier(0.34,1.56,0.64,1);
  max-width: 320px;
  min-width: 220px;
}
.toast.show { transform: translateX(0); }
.toast.hide { transform: translateX(120%); }
.toast-icon { font-size: 1.1rem; flex-shrink: 0; }
.toast-msg { flex: 1; line-height: 1.4; }
.toast.success { border-color: rgba(0,230,118,0.5); }
.toast.success .toast-icon { color: var(--easy); }
.toast.error   { border-color: rgba(239,83,80,0.5); }
.toast.error   .toast-icon { color: var(--hard); }
.toast.info    { border-color: var(--border-hi); }
.toast.info    .toast-icon { color: var(--neon); }

/* ── Loading spinner ──────────────────────────────────────── */
.spinner-wrap {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 4rem;
}
.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border);
  border-top-color: var(--neon);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Empty state ──────────────────────────────────────────── */
.empty-state {
  text-align: center;
  padding: 4rem 2rem;
  color: var(--muted);
}
.empty-state .empty-icon { font-size: 3rem; margin-bottom: 1rem; filter: grayscale(1); opacity: 0.5; }
.empty-state p { font-size: 0.9rem; }

/* ── Topic bars (chart) ───────────────────────────────────── */
.topic-bars { display: flex; flex-direction: column; gap: 10px; }
.topic-bar-item {
  display: flex;
  align-items: center;
  gap: 10px;
  opacity: 0;
}
.topic-bar-label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text);
  width: 180px;
  flex-shrink: 0;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.topic-bar-track {
  flex: 1;
  height: 6px;
  background: rgba(255,255,255,0.05);
  border-radius: 3px;
  overflow: hidden;
}
.topic-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--neon-dim), var(--neon));
  border-radius: 3px;
  width: 0%;
  transition: width 1s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 0 8px var(--neon-glow);
}
.topic-bar-count {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--neon);
  width: 36px;
  text-align: right;
  flex-shrink: 0;
}

/* ── Section titles ───────────────────────────────────────── */
.section-title {
  font-family: var(--font-disp);
  font-size: 1.4rem;
  font-weight: 800;
  color: var(--white);
  margin-bottom: 1.25rem;
  display: flex;
  align-items: center;
  gap: 10px;
}
.section-title .title-line {
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--border-hi), transparent);
}

/* ── Dashboard grid ───────────────────────────────────────── */
.dashboard-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 2rem;
}
.dashboard-panel {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  backdrop-filter: blur(10px);
}
@media (max-width: 768px) {
  .dashboard-grid { grid-template-columns: 1fr; }
}

/* ── Glow borders (animated) ──────────────────────────────── */
.glow-border {
  position: relative;
}
.glow-border::before {
  content: '';
  position: absolute;
  inset: -1px;
  border-radius: inherit;
  background: linear-gradient(135deg, var(--neon), transparent, var(--neon-dim));
  z-index: -1;
  opacity: 0;
  transition: opacity 0.3s;
  animation: borderGlow 3s linear infinite;
  background-size: 200% 200%;
}
.glow-border:hover::before { opacity: 1; }
@keyframes borderGlow {
  0%   { background-position: 0% 50%; }
  50%  { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

/* ── Rank indicator ───────────────────────────────────────── */
.rank-indicator {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  flex-shrink: 0;
}
.rank-1 { background: var(--neon); color: var(--black); }
.rank-2 { background: rgba(232,255,0,0.5); color: var(--black); }
.rank-3 { background: rgba(232,255,0,0.25); color: var(--neon); }
.rank-n { background: rgba(255,255,255,0.05); color: var(--muted); }

/* ── Animated gradient text ───────────────────────────────── */
.grad-text {
  background: linear-gradient(90deg, var(--neon), #fff, var(--neon));
  background-size: 200% auto;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  animation: gradientShift 4s linear infinite;
}
@keyframes gradientShift {
  0%   { background-position: 0% center; }
  100% { background-position: 200% center; }
}

/* ── Progress ring for stats ──────────────────────────────── */
.progress-ring-wrap {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.5rem;
  flex-wrap: wrap;
  margin: 1rem 0;
}
.ring-item { text-align: center; }
.ring-label { font-size: 0.75rem; color: var(--muted); margin-top: 0.5rem; text-transform: uppercase; letter-spacing: 0.08em; font-family: var(--font-mono); }
.ring-val   { font-family: var(--font-mono); font-size: 0.85rem; font-weight: 700; }
.ring-val.easy   { color: var(--easy); }
.ring-val.medium { color: var(--medium); }
.ring-val.hard   { color: var(--hard); }

/* ── Responsive ───────────────────────────────────────────── */
@media (max-width: 900px) {
  .section { padding: 1.5rem 1rem 3rem; }
  .navbar { padding: 0 1rem; }
  .nav-links { display: none; }
  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: rgba(5,5,5,0.97);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    padding: 1rem;
    gap: 0.25rem;
    z-index: 99;
  }
  .nav-hamburger { display: flex; }
  .problems-grid { grid-template-columns: 1fr; }
  .stats-grid { grid-template-columns: repeat(2,1fr); }
  .topic-bar-label { width: 110px; }
}

@media (max-width: 480px) {
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .modal { padding: 1.25rem; }
  .tabs-row { gap: 0.35rem; }
  .tab-btn { padding: 5px 12px; font-size: 0.8rem; }
}

/* ── Code block style for description ─────────────────────── */
.modal-desc code {
  background: rgba(232,255,0,0.08);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 5px;
  font-family: var(--font-mono);
  font-size: 0.85em;
  color: var(--neon);
}

/* ── Skeleton loading ─────────────────────────────────────── */
.skeleton {
  background: linear-gradient(90deg, rgba(255,255,255,0.04) 25%, rgba(255,255,255,0.08) 50%, rgba(255,255,255,0.04) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: 6px;
}
@keyframes shimmer {
  0%   { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ── Scroll reveal class ──────────────────────────────────── */
.reveal { opacity: 0; transform: translateY(24px); }
.reveal.revealed { opacity: 1; transform: none; transition: opacity 0.6s ease, transform 0.6s ease; }