:root {
  --bg: #0d0d0f;
  --bg2: #141418;
  --bg3: #1c1c22;
  --bg4: #232329;
  --border: rgba(255,255,255,0.07);
  --border2: rgba(255,255,255,0.12);
  --text: #f0f0f2;
  --text2: #9898a8;
  --text3: #5a5a6a;
  --accent: #6c63ff;
  --accent2: #8b85ff;
  --accent-bg: rgba(108,99,255,0.12);
  --green: #22c984;
  --green-bg: rgba(34,201,132,0.1);
  --amber: #f5a623;
  --amber-bg: rgba(245,166,35,0.1);
  --red: #f06060;
  --red-bg: rgba(240,96,96,0.1);
  --blue: #4ea8de;
  --blue-bg: rgba(78,168,222,0.1);
  --radius: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --font-display: 'Syne', sans-serif;
  --font-body: 'DM Sans', sans-serif;
  --font-mono: 'DM Mono', monospace;
  --shadow: 0 2px 20px rgba(0,0,0,0.4);
}
[data-theme="light"] {
  --bg: #f7f7fb;
  --bg2: #ffffff;
  --bg3: #f0f0f5;
  --bg4: #e8e8f0;
  --border: rgba(0,0,0,0.07);
  --border2: rgba(0,0,0,0.12);
  --text: #12121a;
  --text2: #5a5a72;
  --text3: #9898b0;
  --accent: #5b52f0;
  --accent2: #7b74ff;
  --accent-bg: rgba(91,82,240,0.08);
  --green: #16a065;
  --green-bg: rgba(22,160,101,0.08);
  --amber: #c47d0a;
  --amber-bg: rgba(196,125,10,0.08);
  --red: #d04040;
  --red-bg: rgba(208,64,64,0.08);
  --blue: #2478b5;
  --blue-bg: rgba(36,120,181,0.08);
  --shadow: 0 2px 20px rgba(0,0,0,0.08);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  font-size: 14px;
  line-height: 1.6;
  transition: background 0.3s, color 0.3s;
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--bg4); border-radius: 3px; }

/* ── Layout ── */
.layout { display: flex; min-height: 100vh; }
.sidebar {
  width: 240px;
  flex-shrink: 0;
  background: var(--bg2);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0; left: 0;
  height: 100vh;
  overflow-y: auto;
  z-index: 100;
  transition: transform 0.3s;
}
.main {
  margin-left: 240px;
  flex: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
.topnav {
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  padding: 0 2rem;
  height: 60px;
  display: flex;
  align-items: center;
  gap: 16px;
  position: sticky;
  top: 0;
  z-index: 50;
}
.content { padding: 2rem; flex: 1; max-width: 1000px; }

/* ── Logo ── */
.logo {
  padding: 1.5rem 1.25rem 1rem;
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.5px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.logo-icon {
  width: 32px; height: 32px;
  background: var(--accent);
  border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  font-size: 16px;
  color: #fff;
  font-family: var(--font-mono);
  font-weight: 500;
}
.logo-text { color: var(--text); }
.logo-text span { color: var(--accent); }

/* ── Sidebar nav ── */
.nav-section { padding: 0.5rem 0; }
.nav-label {
  padding: 0.25rem 1.25rem;
  font-size: 10px;
  font-weight: 500;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--text3);
  font-family: var(--font-display);
}
.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 1.25rem;
  color: var(--text2);
  font-size: 13px;
  cursor: pointer;
  border-radius: 0;
  transition: all 0.15s;
  border-left: 2px solid transparent;
  font-family: var(--font-body);
}
.nav-item:hover { background: var(--bg3); color: var(--text); }
.nav-item.active { background: var(--accent-bg); color: var(--accent2); border-left-color: var(--accent); }
.nav-icon { font-size: 15px; width: 18px; text-align: center; }
.nav-badge {
  margin-left: auto;
  background: var(--bg4);
  color: var(--text3);
  font-size: 10px;
  padding: 1px 6px;
  border-radius: 10px;
  font-family: var(--font-mono);
}
.nav-item.active .nav-badge { background: var(--accent-bg); color: var(--accent2); }

/* ── Sidebar bottom ── */
.sidebar-bottom {
  margin-top: auto;
  padding: 1rem 1.25rem;
  border-top: 1px solid var(--border);
}
.streak-card {
  background: var(--amber-bg);
  border: 1px solid rgba(245,166,35,0.2);
  border-radius: var(--radius);
  padding: 10px 12px;
  margin-bottom: 10px;
}
.streak-top { font-size: 11px; color: var(--amber); font-weight: 500; margin-bottom: 4px; }
.streak-num { font-family: var(--font-display); font-size: 28px; font-weight: 700; color: var(--amber); line-height: 1; }
.streak-sub { font-size: 11px; color: var(--text3); margin-top: 2px; }
.streak-best { font-size: 10px; color: var(--text3); margin-top: 6px; padding-top: 6px; border-top: 1px solid rgba(245,166,35,0.15); }
.streak-best span { color: var(--amber); font-weight: 600; }
.streak-dots { display: flex; gap: 4px; margin-top: 8px; }
.streak-dot {
  width: 20px; height: 20px; border-radius: 5px;
  background: var(--bg4); border: 1px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  font-size: 8px; color: var(--text3); flex: 1;
  transition: background 0.2s;
}
.streak-dot.active { background: var(--amber); border-color: var(--amber); color: #000; font-weight: 700; }
.streak-dot.today { outline: 2px solid var(--amber); outline-offset: 1px; }
.streak-dot-label { font-size: 9px; color: var(--text3); text-align: center; margin-top: 3px; display: flex; gap: 4px; }
.streak-dot-label span { flex: 1; text-align: center; }
@keyframes streakPulse { 0%,100%{transform:scale(1)} 50%{transform:scale(1.15)} }
.streak-num.pulse { animation: streakPulse 0.4s ease; }

/* ── Top nav ── */
.search-wrap { flex: 1; position: relative; max-width: 400px; }
.search-wrap input {
  width: 100%;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 8px 12px 8px 36px;
  font-size: 13px;
  color: var(--text);
  font-family: var(--font-body);
  transition: border-color 0.2s;
}
.search-wrap input:focus { outline: none; border-color: var(--accent); }
.search-wrap input::placeholder { color: var(--text3); }
.search-icon {
  position: absolute; left: 11px; top: 50%;
  transform: translateY(-50%);
  color: var(--text3); font-size: 14px; pointer-events: none;
}
.nav-filters { display: flex; gap: 8px; }
.filter-select {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 7px 10px;
  font-size: 12px;
  color: var(--text2);
  font-family: var(--font-body);
  cursor: pointer;
}
.filter-select:focus { outline: none; border-color: var(--accent); }
.theme-toggle {
  width: 36px; height: 36px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg3);
  color: var(--text2);
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  font-size: 16px;
  transition: all 0.2s;
}
.theme-toggle:hover { border-color: var(--accent); color: var(--accent); }
.hamburger { display: none; }

/* ── Stats grid ── */
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-bottom: 2rem; }
.stat-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px 18px;
}
.stat-card-label { font-size: 11px; color: var(--text3); text-transform: uppercase; letter-spacing: 1px; font-family: var(--font-display); font-weight: 500; margin-bottom: 6px; }
.stat-card-val { font-family: var(--font-display); font-size: 28px; font-weight: 700; color: var(--text); line-height: 1; margin-bottom: 4px; }
.stat-card-sub { font-size: 11px; color: var(--text3); }
.mini-prog { height: 3px; background: var(--bg4); border-radius: 2px; margin-top: 10px; overflow: hidden; }
.mini-prog-fill { height: 100%; border-radius: 2px; background: var(--accent); transition: width 0.5s ease; }

/* ── Page header ── */
.page-header { margin-bottom: 1.5rem; }
.page-title { font-family: var(--font-display); font-size: 22px; font-weight: 600; color: var(--text); margin-bottom: 4px; }
.page-sub { font-size: 13px; color: var(--text2); }

/* ── View tabs ── */
.view-tabs { display: flex; gap: 4px; background: var(--bg3); border-radius: var(--radius-lg); padding: 4px; width: fit-content; margin-bottom: 1.5rem; }
.vtab {
  padding: 6px 16px;
  border-radius: var(--radius);
  border: none;
  background: transparent;
  color: var(--text2);
  font-size: 13px;
  cursor: pointer;
  font-family: var(--font-body);
  font-weight: 400;
  transition: all 0.2s;
}
.vtab.active { background: var(--bg2); color: var(--text); box-shadow: var(--shadow); }
.vtab:hover:not(.active) { color: var(--text); }

/* ── AI Panel ── */
.ai-panel {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
  position: relative;
  overflow: hidden;
}
.ai-panel::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--green));
}
.ai-panel-head { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.ai-indicator {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--green);
  box-shadow: 0 0 8px var(--green);
  animation: pulse 2s infinite;
}
@keyframes pulse { 0%,100%{opacity:1} 50%{opacity:0.4} }
.ai-panel-title { font-size: 13px; font-weight: 500; color: var(--text); font-family: var(--font-display); }
.ai-panel-sub { font-size: 11px; color: var(--text3); margin-left: auto; }
.ai-btns { display: flex; gap: 8px; flex-wrap: wrap; }
.ai-btn {
  padding: 6px 14px;
  border-radius: 20px;
  border: 1px solid var(--border2);
  background: var(--bg3);
  color: var(--text2);
  font-size: 12px;
  cursor: pointer;
  font-family: var(--font-body);
  transition: all 0.2s;
  display: flex; align-items: center; gap: 6px;
}
.ai-btn:hover { background: var(--accent-bg); border-color: var(--accent); color: var(--accent2); }
.ai-response {
  margin-top: 12px;
  padding: 12px;
  background: var(--bg3);
  border-radius: var(--radius);
  font-size: 13px;
  color: var(--text2);
  line-height: 1.7;
  display: none;
  border-left: 2px solid var(--accent);
}
.ai-response.visible { display: block; }
.ai-response .loading-dots { display: inline-flex; gap: 4px; }
.ai-response .loading-dots span {
  width: 5px; height: 5px; border-radius: 50%;
  background: var(--accent);
  animation: bounce 1.2s infinite;
}
.ai-response .loading-dots span:nth-child(2) { animation-delay: 0.2s; }
.ai-response .loading-dots span:nth-child(3) { animation-delay: 0.4s; }
@keyframes bounce { 0%,80%,100%{transform:translateY(0)} 40%{transform:translateY(-6px)} }
.ai-custom-row { display: flex; gap: 8px; margin-top: 10px; }
.ai-custom-input {
  flex: 1;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 8px 12px;
  font-size: 13px;
  color: var(--text);
  font-family: var(--font-body);
}
.ai-custom-input:focus { outline: none; border-color: var(--accent); }
.ai-custom-input::placeholder { color: var(--text3); }
.ai-send-btn {
  padding: 8px 16px;
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 13px;
  cursor: pointer;
  font-family: var(--font-body);
  font-weight: 500;
  transition: opacity 0.2s;
}
.ai-send-btn:hover { opacity: 0.85; }
.ai-send-btn:disabled { opacity: 0.4; cursor: not-allowed; }

/* ── Topic block ── */
.topic-block { margin-bottom: 1.25rem; }
.topic-hdr {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all 0.2s;
}
.topic-hdr:hover { border-color: var(--border2); }
.topic-hdr.open { border-radius: var(--radius-lg) var(--radius-lg) 0 0; border-bottom-color: transparent; }
.t-color-bar { width: 10px; height: 10px; border-radius: 50%; flex-shrink: 0; }
.t-name { font-family: var(--font-display); font-size: 14px; font-weight: 600; color: var(--text); flex: 1; }
.t-patterns-count {
  font-size: 11px;
  color: var(--text3);
  background: var(--bg4);
  padding: 2px 8px;
  border-radius: 10px;
  font-family: var(--font-mono);
}
.t-progress { display: flex; align-items: center; gap: 8px; }
.t-prog-bar { width: 60px; height: 3px; background: var(--bg4); border-radius: 2px; overflow: hidden; }
.t-prog-fill { height: 100%; border-radius: 2px; transition: width 0.4s; }
.t-prog-text { font-size: 11px; color: var(--text3); font-family: var(--font-mono); min-width: 32px; text-align: right; }
.t-chevron { color: var(--text3); font-size: 12px; transition: transform 0.2s; flex-shrink: 0; }
.t-chevron.open { transform: rotate(90deg); }
.topic-body {
  border: 1px solid var(--border);
  border-top: none;
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  overflow: hidden;
  display: none;
}
.topic-body.visible { display: block; }

/* ── Pattern block ── */
.pat-block { border-bottom: 1px solid var(--border); }
.pat-block:last-child { border-bottom: none; }
.pat-hdr {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 16px 10px 32px;
  background: var(--bg3);
  cursor: pointer;
  transition: background 0.15s;
}
.pat-hdr:hover { background: var(--bg4); }
.pat-dot { width: 6px; height: 6px; border-radius: 50%; flex-shrink: 0; }
.pat-name-wrap { flex: 1; display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.pat-name { font-size: 13px; font-weight: 500; color: var(--text); font-family: var(--font-display); }
.pat-desc { font-size: 11px; color: var(--text3); }
.pat-count { font-size: 11px; color: var(--text3); font-family: var(--font-mono); }
.pat-chevron { color: var(--text3); font-size: 11px; transition: transform 0.2s; }
.pat-chevron.open { transform: rotate(90deg); }
.pat-body { padding: 6px 8px; display: none; background: var(--bg2); }
.pat-body.visible { display: grid; gap: 4px; }

/* ── Question row ── */
.qrow {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 12px;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background 0.15s;
  border: 1px solid transparent;
}
.qrow:hover { background: var(--bg3); border-color: var(--border); }
.qrow.solved { opacity: 0.45; }
.qidx { font-size: 11px; color: var(--text3); min-width: 26px; font-family: var(--font-mono); }
.qtitle { font-size: 13px; color: var(--text); flex: 1; }
.qtags { display: flex; gap: 6px; align-items: center; flex-shrink: 0; flex-wrap: wrap; }
.co-tag {
  padding: 2px 7px; border-radius: 20px;
  font-size: 10px; background: var(--blue-bg);
  color: var(--blue); border: 1px solid rgba(78,168,222,0.2);
  font-family: var(--font-mono);
}
.pat-tag {
  padding: 2px 7px; border-radius: 20px; font-size: 10px;
  background: var(--accent-bg); color: var(--accent2);
  border: 1px solid rgba(108,99,255,0.2);
}
.diff {
  padding: 2px 8px; border-radius: 20px; font-size: 10px; font-weight: 500;
  font-family: var(--font-mono);
}
.diff.Easy { background: var(--green-bg); color: var(--green); }
.diff.Medium { background: var(--amber-bg); color: var(--amber); }
.diff.Hard { background: var(--red-bg); color: var(--red); }
.chk {
  width: 18px; height: 18px; border-radius: 50%;
  border: 1.5px solid var(--border2);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0; font-size: 10px; cursor: pointer;
  transition: all 0.2s;
}
.chk:hover { border-color: var(--green); }
.chk.done { background: var(--green); border-color: var(--green); color: #fff; }

.lc-btn {
  display: inline-flex; align-items: center; gap: 4px;
  padding: 2px 8px; border-radius: 20px;
  font-size: 10px; font-weight: 500;
  background: rgba(255,161,22,0.1);
  color: #ffa116;
  border: 1px solid rgba(255,161,22,0.25);
  text-decoration: none;
  font-family: var(--font-mono);
  transition: all 0.15s;
  cursor: pointer;
  white-space: nowrap;
}
.lc-btn:hover { background: rgba(255,161,22,0.2); border-color: rgba(255,161,22,0.5); }
.lc-btn svg { width: 10px; height: 10px; fill: #ffa116; }

/* ── Pattern-only view ── */
.pat-only-block {
  margin-bottom: 1rem;
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}
.pat-only-hdr {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 16px;
  cursor: pointer;
  transition: background 0.15s;
}
.pat-only-hdr:hover { background: var(--bg3); }
.pat-only-name { font-family: var(--font-display); font-size: 14px; font-weight: 600; color: var(--text); flex: 1; }
.pat-only-meta { font-size: 11px; color: var(--text3); font-family: var(--font-mono); }
.pat-only-body { padding: 6px 8px; border-top: 1px solid var(--border); display: none; }
.pat-only-body.visible { display: grid; gap: 4px; }

/* ── Roadmap view ── */
.roadmap-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 12px; }
.rm-card {
  background: var(--bg2);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s;
  position: relative;
  overflow: hidden;
}
.rm-card:hover { border-color: var(--border2); transform: translateY(-1px); }
.rm-num {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text3);
  margin-bottom: 8px;
  display: flex; align-items: center; gap: 6px;
}
.rm-step {
  width: 20px; height: 20px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 10px; font-weight: 500; color: #fff;
}
.rm-name { font-family: var(--font-display); font-size: 14px; font-weight: 600; color: var(--text); margin-bottom: 4px; }
.rm-patterns { font-size: 11px; color: var(--text3); margin-bottom: 12px; }
.rm-prog-wrap { display: flex; align-items: center; gap: 8px; }
.rm-prog-bar { flex: 1; height: 3px; background: var(--bg4); border-radius: 2px; overflow: hidden; }
.rm-prog-fill { height: 100%; border-radius: 2px; }
.rm-prog-pct { font-size: 10px; color: var(--text3); font-family: var(--font-mono); min-width: 28px; text-align: right; }

/* ── Company chips ── */
.co-chips { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 1rem; }
.co-chip {
  padding: 6px 14px;
  border-radius: 20px;
  border: 1px solid var(--border2);
  background: var(--bg3);
  color: var(--text2);
  font-size: 12px;
  cursor: pointer;
  font-family: var(--font-body);
  transition: all 0.2s;
}
.co-chip:hover { color: var(--text); border-color: var(--border2); }
.co-chip.active { background: var(--accent-bg); border-color: var(--accent); color: var(--accent2); }

/* ── Empty state ── */
.empty {
  text-align: center;
  padding: 4rem 2rem;
  color: var(--text3);
  font-size: 14px;
}
.empty-icon { font-size: 40px; margin-bottom: 12px; }

/* ── Mobile ── */
@media (max-width: 768px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); }
  .main { margin-left: 0; }
  .hamburger { display: flex; align-items: center; justify-content: center; width: 36px; height: 36px; background: var(--bg3); border: 1px solid var(--border); border-radius: var(--radius); cursor: pointer; font-size: 18px; color: var(--text2); }
  .stats-grid { grid-template-columns: repeat(2,1fr); }
  .content { padding: 1rem; }
  .roadmap-grid { grid-template-columns: 1fr 1fr; }
}

/* ── Animations ── */
@keyframes fadeIn { from{opacity:0;transform:translateY(8px)} to{opacity:1;transform:translateY(0)} }
.topic-block, .pat-only-block, .rm-card { animation: fadeIn 0.3s ease both; }

/* ── Page sections ── */
.page { display: none; }
.page.active { display: block; }