/* ===== Reset & Variables ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg-dark: #0d1117;
  --bg-sidebar: #161b22;
  --bg-card: #1c2128;
  --bg-code: #0d1117;
  --accent: #f78166;
  --accent-blue: #79c0ff;
  --accent-green: #56d364;
  --accent-yellow: #e3b341;
  --easy: #3fb950;
  --medium: #d29922;
  --hard: #f85149;
  --text-primary: #e6edf3;
  --text-secondary: #7d8590;
  --text-dim: #484f58;
  --border: #30363d;
  --hover: #21262d;
  --highlight-active: #264f78;
  --highlight-found: #1a472a;
  --highlight-pointer: #3d2b00;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
  --radius: 8px;
}

html, body { height: 100%; font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; background: var(--bg-dark); color: var(--text-primary); }

.hidden { display: none !important; }

/* ===== Layout ===== */
#app {
  display: grid;
  grid-template-columns: 260px 1fr;
  height: 100vh;
  overflow: hidden;
}

/* ===== Sidebar ===== */
#sidebar {
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.sidebar-header {
  padding: 14px 14px 10px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.logo { display: flex; align-items: center; gap: 8px; margin-bottom: 2px; }
.logo-icon { font-size: 20px; }
.logo-text { font-size: 16px; font-weight: 800; color: var(--text-primary); letter-spacing: -0.5px; }
.logo-fyi  { color: var(--accent); font-weight: 400; }
.sidebar-subtitle { font-size: 10px; color: var(--text-secondary); text-transform: uppercase; letter-spacing: 1px; }

/* ── Section Nav ── */
#section-nav {
  padding: 6px 8px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.section-nav-item {
  display: flex;
  align-items: center;
  gap: 9px;
  padding: 7px 10px;
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.12s;
  margin-bottom: 1px;
}
.section-nav-item:hover { background: var(--hover); }
.section-nav-item.active { background: #162032; }

.sni-icon { font-size: 14px; flex-shrink: 0; }
.sni-name {
  flex: 1;
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  transition: color 0.12s;
}
.section-nav-item:hover .sni-name { color: var(--text-primary); }
.section-nav-item.active .sni-name { color: var(--accent-blue); }

.sni-pill {
  font-size: 9px;
  padding: 1px 6px;
  border-radius: 10px;
  background: var(--bg-dark);
  color: var(--text-dim);
  border: 1px solid var(--border);
  font-weight: 600;
  letter-spacing: 0.3px;
}

/* ── Algo Sub-nav (Patterns / LC75 / LC150) ── */
#algo-subnav {
  display: flex;
  gap: 4px;
  padding: 8px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.algo-tab {
  flex: 1;
  padding: 5px 4px;
  border: 1px solid var(--border);
  border-radius: 5px;
  background: transparent;
  color: var(--text-secondary);
  font-size: 11px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.12s;
  text-align: center;
}
.algo-tab:hover { background: var(--hover); color: var(--text-primary); }
.algo-tab.active { background: var(--accent-blue); border-color: var(--accent-blue); color: #0d1117; }

/* ── Search ── */
#sidebar-search-wrap { padding: 8px 8px 4px; flex-shrink: 0; }
#sidebar-search {
  width: 100%;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 6px 10px;
  font-size: 12px;
  color: var(--text-primary);
  outline: none;
  transition: border-color 0.15s;
}
#sidebar-search:focus { border-color: var(--accent-blue); }
#sidebar-search::placeholder { color: var(--text-dim); }

/* ── Pattern list scroll area ── */
#sidebar-body { flex: 1; overflow-y: auto; }
#sidebar-body::-webkit-scrollbar { width: 4px; }
#sidebar-body::-webkit-scrollbar-thumb { background: var(--border); border-radius: 2px; }

#pattern-list { padding: 4px 0; }

/* ── Pattern Sections ── */
.pattern-section { border-bottom: 1px solid rgba(48,54,61,0.5); }

.pattern-header {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 8px 14px;
  cursor: pointer;
  transition: background 0.12s;
  user-select: none;
}
.pattern-header:hover { background: var(--hover); }

.ph-icon  { font-size: 14px; flex-shrink: 0; }
.ph-name  { font-size: 12px; font-weight: 600; color: var(--text-secondary); flex: 1; transition: color 0.15s; }
.pattern-header:hover .ph-name,
.pattern-header.expanded .ph-name { color: var(--pcolor, var(--text-primary)); }
.ph-count { font-size: 10px; color: var(--text-dim); white-space: nowrap; }
.ph-done  { color: var(--pcolor, var(--accent-green)); font-weight: 700; }
.ph-total { color: var(--text-dim); }
.ph-chevron {
  font-size: 13px;
  color: var(--text-dim);
  transition: transform 0.2s;
  font-style: normal;
  line-height: 1;
}
.pattern-header.expanded .ph-chevron { transform: rotate(90deg); color: var(--pcolor, var(--accent-blue)); }

/* ── Pattern Question List ── */
.pattern-qlist {
  display: none;
  background: rgba(0,0,0,0.15);
}
.pattern-qlist.open { display: block; }

.pq-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 6px 14px 6px 28px;
  cursor: pointer;
  transition: background 0.12s;
  font-size: 12px;
}
.pq-item:hover { background: var(--hover); }
.pq-item.active { background: #162032; }
.pq-item.pq-soon { cursor: default; }
.pq-item.pq-soon:hover { background: transparent; }

.pq-num  { color: var(--text-dim); min-width: 32px; font-size: 10px; font-weight: 600; }
.pq-name { flex: 1; color: var(--text-primary); line-height: 1.3; }
.pq-item.pq-soon .pq-name { color: var(--text-secondary); }

.diff-badge {
  font-size: 9px;
  font-weight: 700;
  padding: 1px 5px;
  border-radius: 3px;
  text-transform: uppercase;
  letter-spacing: 0.3px;
  flex-shrink: 0;
}
.diff-badge.easy   { color: var(--easy);   background: rgba(63,185,80,0.12); }
.diff-badge.medium { color: var(--medium); background: rgba(210,153,34,0.12); }
.diff-badge.hard   { color: var(--hard);   background: rgba(248,81,73,0.12); }
.diff-badge.soon   { opacity: 0.6; }
.pq-item.pq-soon .pq-name { color: var(--text-secondary); }

/* ===== Main Content ===== */
#main {
  overflow-y: auto;
  padding: 0;
}

#main::-webkit-scrollbar { width: 6px; }
#main::-webkit-scrollbar-track { background: transparent; }
#main::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* ===== Welcome Screen ===== */
#welcome-screen {
  overflow-y: auto;
  padding: 40px 32px 60px;
}
#welcome-screen::-webkit-scrollbar { width: 6px; }
#welcome-screen::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

.welcome-hero {
  text-align: center;
  max-width: 660px;
  margin: 0 auto 48px;
  padding-top: 24px;
}
.welcome-icon { font-size: 56px; margin-bottom: 16px; }
.welcome-hero h1 { font-size: 36px; font-weight: 800; margin-bottom: 12px; color: var(--accent); }
.welcome-hero > p { color: var(--text-secondary); font-size: 15px; line-height: 1.8; margin-bottom: 28px; }

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 32px;
  flex-wrap: wrap;
}
.hero-stat span {
  display: block;
  font-size: 28px;
  font-weight: 800;
  color: var(--accent-blue);
  line-height: 1;
  margin-bottom: 4px;
}
.hero-stat label { font-size: 11px; color: var(--text-secondary); text-transform: uppercase; letter-spacing: 0.8px; }

/* Pattern cards grid */
.patterns-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
  max-width: 1100px;
  margin: 0 auto;
}

.pattern-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px 16px 14px;
  cursor: pointer;
  transition: border-color 0.15s, transform 0.15s, background 0.15s;
  position: relative;
  overflow: hidden;
}
.pattern-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: var(--pcolor, var(--accent-blue));
  opacity: 0;
  transition: opacity 0.15s;
}
.pattern-card:hover {
  border-color: var(--pcolor, var(--accent-blue));
  background: var(--hover);
  transform: translateY(-2px);
}
.pattern-card:hover::before { opacity: 1; }

.pc-icon  { font-size: 24px; margin-bottom: 8px; }
.pc-name  { font-size: 13px; font-weight: 700; color: var(--text-primary); margin-bottom: 6px; }
.pc-desc  { font-size: 11px; color: var(--text-secondary); line-height: 1.6; margin-bottom: 12px; min-height: 50px; }
.pc-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 10px;
  color: var(--text-dim);
  border-top: 1px solid var(--border);
  padding-top: 8px;
}
.pc-count { color: var(--pcolor, var(--accent-green)); font-weight: 700; }
.pc-total { color: var(--text-dim); }

/* ===== Pattern Detail View ===== */
#pattern-view {
  overflow-y: auto;
  padding: 32px;
}
#pattern-view::-webkit-scrollbar { width: 6px; }
#pattern-view::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

#pattern-header-detail {
  display: flex;
  align-items: flex-start;
  gap: 20px;
  margin-bottom: 20px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border);
}
.pattern-detail-icon {
  font-size: 48px;
  width: 72px;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  flex-shrink: 0;
}
.pattern-detail-text h2 { font-size: 24px; font-weight: 800; margin-bottom: 8px; }
#pv-description { color: var(--text-secondary); font-size: 14px; line-height: 1.7; }

.insight-box {
  background: rgba(227,179,65,0.08);
  border: 1px solid rgba(227,179,65,0.25);
  border-left: 3px solid var(--accent-yellow);
  border-radius: var(--radius);
  padding: 12px 16px;
  font-size: 13px;
  color: var(--text-primary);
  line-height: 1.6;
  margin-bottom: 28px;
}
.insight-box strong { color: var(--accent-yellow); }

.pattern-q-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
}

.pq-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
}
.pq-card:hover { border-color: var(--accent-blue); background: var(--hover); }
.pq-card-soon { cursor: default; }
.pq-card-soon:hover { border-color: var(--border); background: var(--bg-card); }

.pqc-num   { font-size: 10px; color: var(--text-dim); font-weight: 700; margin-bottom: 4px; }
.pqc-title { font-size: 13px; font-weight: 600; color: var(--text-primary); margin-bottom: 10px; line-height: 1.4; }
.pqc-footer { display: flex; justify-content: space-between; align-items: center; }
.pqc-go   { font-size: 11px; color: var(--accent-blue); font-weight: 600; }
.pqc-soon { font-size: 11px; color: var(--text-dim); }

/* ===== Question View ===== */
#question-view { padding: 0; }

#question-header {
  padding: 24px 32px 16px;
  border-bottom: 1px solid var(--border);
  background: var(--bg-sidebar);
}

.question-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}

.q-number {
  font-size: 13px;
  color: var(--text-secondary);
  font-weight: 600;
}

.question-meta h2 {
  font-size: 22px;
  font-weight: 700;
}

.badge {
  font-size: 11px;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 20px;
  text-transform: capitalize;
}
.badge.easy { color: var(--easy); background: rgba(63,185,80,0.1); border: 1px solid rgba(63,185,80,0.2); }
.badge.medium { color: var(--medium); background: rgba(210,153,34,0.1); border: 1px solid rgba(210,153,34,0.2); }
.badge.hard { color: var(--hard); background: rgba(248,81,73,0.1); border: 1px solid rgba(248,81,73,0.2); }

.tags { display: flex; gap: 8px; flex-wrap: wrap; }
.tag {
  font-size: 11px;
  padding: 3px 10px;
  border-radius: 4px;
  background: var(--hover);
  color: var(--text-secondary);
  border: 1px solid var(--border);
}

/* ===== Problem Description ===== */
#problem-section {
  padding: 24px 32px;
  border-bottom: 1px solid var(--border);
}

.description-text {
  font-size: 14px;
  line-height: 1.8;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.description-text code {
  background: var(--hover);
  padding: 1px 6px;
  border-radius: 4px;
  font-family: 'Courier New', monospace;
  font-size: 13px;
  color: var(--accent-blue);
}

.examples { display: flex; gap: 16px; flex-wrap: wrap; }

.example-box {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  font-size: 13px;
  flex: 1;
  min-width: 200px;
}

.example-box .ex-label { color: var(--text-secondary); font-size: 11px; font-weight: 600; margin-bottom: 8px; text-transform: uppercase; }
.example-box .ex-line { font-family: monospace; margin-bottom: 4px; }
.example-box .ex-line span { color: var(--text-secondary); }
.example-box .ex-val { color: var(--accent-blue); }
.example-box .ex-out { color: var(--accent-green); }

/* ===== Solutions ===== */
#solutions-section {
  padding: 24px 32px;
}

.section-title {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 16px;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
  font-size: 12px;
}

.solution-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.sol-tab {
  padding: 8px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 13px;
  font-weight: 500;
  transition: all 0.15s;
  display: flex;
  align-items: center;
  gap: 8px;
}

.sol-tab:hover { border-color: var(--accent-blue); color: var(--text-primary); }
.sol-tab.active { background: #162032; border-color: #1f6feb; color: var(--accent-blue); }

.sol-tab .tab-rank {
  font-size: 10px;
  padding: 1px 6px;
  border-radius: 3px;
  font-weight: 700;
}
.tab-rank.worst { background: rgba(248,81,73,0.2); color: var(--hard); }
.tab-rank.better { background: rgba(210,153,34,0.2); color: var(--medium); }
.tab-rank.best { background: rgba(63,185,80,0.2); color: var(--easy); }

/* ===== Solution Panel ===== */
#solution-info {
  margin-bottom: 16px;
  display: flex;
  align-items: flex-start;
  gap: 16px;
  flex-wrap: wrap;
}

.complexity-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.complexity-badge {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: var(--radius);
  font-size: 13px;
  font-weight: 600;
  border: 1px solid;
}
.complexity-badge.time { background: rgba(121,192,255,0.1); border-color: rgba(121,192,255,0.2); color: var(--accent-blue); }
.complexity-badge.space { background: rgba(247,129,102,0.1); border-color: rgba(247,129,102,0.2); color: var(--accent); }
.complexity-badge .cx-label { font-size: 10px; font-weight: 400; color: var(--text-secondary); }

.solution-explanation {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
  flex: 1;
  min-width: 200px;
}

#solution-body {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  min-height: 400px;
}

@media (max-width: 900px) {
  #solution-body { grid-template-columns: 1fr; }
}

#code-panel, #viz-panel {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.panel-header {
  padding: 10px 16px;
  background: var(--bg-sidebar);
  border-bottom: 1px solid var(--border);
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
}

#code-panel pre {
  flex: 1;
  overflow: auto;
  margin: 0;
}

#code-panel pre::-webkit-scrollbar { width: 4px; height: 4px; }
#code-panel pre::-webkit-scrollbar-thumb { background: var(--border); }

#code-panel code {
  font-size: 12.5px;
  line-height: 1.7;
  padding: 8px 0 !important;
  background: var(--bg-code) !important;
  display: block;
}

/* ── Per-line code highlighting ── */
.code-line {
  display: block;
  padding: 0 16px;
  border-left: 3px solid transparent;
  transition: background 0.2s, border-color 0.2s;
  border-radius: 0;
  white-space: pre;
}

.code-line.active {
  background: rgba(227, 179, 65, 0.12);
  border-left-color: var(--accent-yellow);
  position: relative;
}

.code-line.active::before {
  content: '▶';
  position: absolute;
  left: 4px;
  color: var(--accent-yellow);
  font-size: 8px;
  top: 50%;
  transform: translateY(-50%);
  opacity: 0.9;
}

/* ===== Visualization ===== */
#viz-container {
  flex: 1;
  padding: 20px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 180px;
  overflow: auto;
}

/* Array Visualization */
.array-viz {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  width: 100%;
}

.array-row {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
  justify-content: center;
}

.array-cell {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 700;
  border: 2px solid var(--border);
  background: var(--bg-dark);
  color: var(--text-primary);
  transition: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
}

.array-cell.highlight-i { background: #1a3a5c; border-color: var(--accent-blue); color: var(--accent-blue); transform: scale(1.1); }
.array-cell.highlight-j { background: #3d2b00; border-color: var(--accent-yellow); color: var(--accent-yellow); transform: scale(1.1); }
.array-cell.highlight-found { background: #1a472a; border-color: var(--accent-green); color: var(--accent-green); transform: scale(1.15); box-shadow: 0 0 12px rgba(86,211,100,0.3); }
.array-cell.highlight-min { background: #1a3a5c; border-color: #79c0ff; color: #79c0ff; }
.array-cell.highlight-curr { background: #3d2b00; border-color: var(--accent-yellow); color: var(--accent-yellow); transform: scale(1.1); }
.array-cell.highlight-window { background: #162032; border-color: var(--accent-blue); }
.array-cell.highlight-max { background: #1a472a; border-color: var(--accent-green); color: var(--accent-green); }
.array-cell.highlight-neg { background: rgba(248,81,73,0.15); border-color: var(--hard); color: var(--hard); }
.array-cell.highlight-char { background: #1a3a5c; border-color: var(--accent-blue); color: var(--accent-blue); }
.array-cell.highlight-match { background: #1a472a; border-color: var(--accent-green); color: var(--accent-green); }
.array-cell.highlight-mismatch { background: rgba(248,81,73,0.15); border-color: var(--hard); }
.array-cell.highlight-removed { opacity: 0.25; transform: scale(0.85); }

.array-indices {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
  justify-content: center;
}

.array-index {
  width: 44px;
  text-align: center;
  font-size: 10px;
  color: var(--text-dim);
}

.pointer-row {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
  justify-content: center;
  min-height: 20px;
}

.pointer-cell {
  width: 44px;
  text-align: center;
  font-size: 10px;
  font-weight: 700;
  color: transparent;
  transition: color 0.2s;
}

.pointer-cell.ptr-i { color: var(--accent-blue); }
.pointer-cell.ptr-j { color: var(--accent-yellow); }
.pointer-cell.ptr-min { color: #79c0ff; }
.pointer-cell.ptr-curr { color: var(--accent-yellow); }
.pointer-cell.ptr-max { color: var(--accent-green); }

/* Stack Visualization */
.stack-viz {
  display: flex;
  gap: 24px;
  align-items: flex-start;
  width: 100%;
  justify-content: center;
}

.stack-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.stack-label {
  font-size: 11px;
  color: var(--text-secondary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 4px;
}

.stack-elements {
  display: flex;
  flex-direction: column-reverse;
  gap: 3px;
  min-height: 120px;
  border: 2px dashed var(--border);
  border-radius: 6px;
  padding: 8px;
  min-width: 64px;
  align-items: center;
  justify-content: flex-start;
}

.stack-cell {
  width: 50px;
  height: 34px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 5px;
  font-size: 16px;
  font-weight: 700;
  border: 2px solid var(--border);
  background: var(--bg-dark);
  transition: all 0.3s ease;
}

.stack-cell.top { border-color: var(--accent-blue); background: #1a3a5c; color: var(--accent-blue); }
.stack-cell.matched { border-color: var(--accent-green); background: #1a472a; color: var(--accent-green); }
.stack-cell.mismatch { border-color: var(--hard); background: rgba(248,81,73,0.1); color: var(--hard); }

.string-display {
  display: flex;
  gap: 4px;
  flex-wrap: wrap;
  justify-content: center;
  margin-bottom: 8px;
}

/* Linked List Visualization */
.linked-list-viz {
  display: flex;
  flex-direction: column;
  gap: 16px;
  width: 100%;
  align-items: center;
}

.list-row {
  display: flex;
  align-items: center;
  gap: 0;
  flex-wrap: wrap;
  justify-content: center;
}

.list-node {
  display: flex;
  align-items: center;
}

.node-box {
  width: 48px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 2px solid var(--border);
  border-radius: 6px;
  background: var(--bg-dark);
  font-size: 15px;
  font-weight: 700;
  transition: all 0.35s ease;
  position: relative;
}

.node-box.highlight-prev { border-color: var(--accent); color: var(--accent); background: rgba(247,129,102,0.1); }
.node-box.highlight-curr { border-color: var(--accent-yellow); color: var(--accent-yellow); background: rgba(227,179,65,0.1); transform: scale(1.1); }
.node-box.highlight-next { border-color: var(--accent-blue); color: var(--accent-blue); background: rgba(121,192,255,0.1); }
.node-box.highlight-done { border-color: var(--accent-green); color: var(--accent-green); background: rgba(86,211,100,0.1); }

.node-arrow {
  width: 28px;
  height: 2px;
  background: var(--border);
  position: relative;
  transition: background 0.3s;
}

.node-arrow::after {
  content: '';
  position: absolute;
  right: -1px;
  top: -4px;
  border: 5px solid transparent;
  border-left: 8px solid var(--border);
}

.node-arrow.active { background: var(--accent-green); }
.node-arrow.active::after { border-left-color: var(--accent-green); }
.node-arrow.reversed { background: var(--accent-blue); }
.node-arrow.reversed::after { border-left-color: var(--accent-blue); }

.node-null {
  width: 36px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 11px;
  color: var(--text-dim);
  font-weight: 600;
}

.list-pointers {
  display: flex;
  gap: 16px;
  font-size: 12px;
}

.list-ptr {
  padding: 3px 10px;
  border-radius: 4px;
  font-weight: 600;
  font-size: 11px;
}
.list-ptr.prev { background: rgba(247,129,102,0.15); color: var(--accent); border: 1px solid var(--accent); }
.list-ptr.curr { background: rgba(227,179,65,0.15); color: var(--accent-yellow); border: 1px solid var(--accent-yellow); }
.list-ptr.nxt { background: rgba(121,192,255,0.15); color: var(--accent-blue); border: 1px solid var(--accent-blue); }

/* Hash Map Visualization */
.hashmap-viz {
  display: flex;
  flex-direction: column;
  gap: 8px;
  width: 100%;
  max-width: 300px;
}

.hashmap-label {
  font-size: 11px;
  color: var(--text-secondary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.hashmap-entries {
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
  min-height: 40px;
}

.hashmap-header {
  display: grid;
  grid-template-columns: 1fr 1fr;
  background: var(--bg-sidebar);
  padding: 6px 12px;
  font-size: 11px;
  color: var(--text-dim);
  font-weight: 600;
  border-bottom: 1px solid var(--border);
}

.hashmap-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  padding: 7px 12px;
  font-size: 13px;
  font-weight: 600;
  border-bottom: 1px solid var(--border);
  transition: all 0.3s;
}

.hashmap-row:last-child { border-bottom: none; }
.hashmap-row.new-entry { background: rgba(121,192,255,0.1); }
.hashmap-row .key { color: var(--accent-yellow); }
.hashmap-row .val { color: var(--accent-blue); }
.hashmap-empty { padding: 12px; text-align: center; color: var(--text-dim); font-size: 12px; }

/* ===== Step Info ===== */
#step-info {
  padding: 10px 16px;
  border-top: 1px solid var(--border);
  background: var(--bg-sidebar);
  min-height: 70px;
}

.step-desc {
  font-size: 13px;
  color: var(--text-primary);
  line-height: 1.5;
  margin-bottom: 8px;
}

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

.var-chip {
  font-size: 12px;
  padding: 3px 10px;
  border-radius: 4px;
  background: var(--hover);
  border: 1px solid var(--border);
  font-family: monospace;
  color: var(--text-secondary);
}

.var-chip .var-name { color: var(--accent-blue); }
.var-chip .var-val { color: var(--accent-yellow); }

/* ===== Controls ===== */
#controls {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 16px;
  border-top: 1px solid var(--border);
  background: var(--bg-dark);
}

#controls button {
  width: 36px;
  height: 36px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-card);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 14px;
  transition: all 0.15s;
  display: flex;
  align-items: center;
  justify-content: center;
}

#controls button:hover { background: var(--hover); border-color: var(--accent-blue); }
#btn-play { background: #1f6feb; border-color: #1f6feb; width: 44px; height: 36px; }
#btn-play:hover { background: #388bfd; border-color: #388bfd; }

.speed-control {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-left: auto;
}

.speed-control label {
  font-size: 11px;
  color: var(--text-secondary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

#speed-slider {
  width: 70px;
  accent-color: var(--accent-blue);
  cursor: pointer;
}

.step-counter {
  font-size: 12px;
  color: var(--text-secondary);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

/* ===== Misc Viz ===== */
.viz-note {
  font-size: 10px;
  color: var(--text-dim);
  text-align: center;
  margin-top: 4px;
}

.profit-display {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-top: 8px;
}

.profit-box {
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 13px;
  font-weight: 700;
  border: 1px solid;
}
.profit-box.min { background: rgba(121,192,255,0.1); border-color: var(--accent-blue); color: var(--accent-blue); }
.profit-box.max { background: rgba(86,211,100,0.1); border-color: var(--accent-green); color: var(--accent-green); }

.subarray-display {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-top: 8px;
}

.subarray-box {
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 13px;
  font-weight: 700;
  border: 1px solid;
}
.subarray-box.curr { background: rgba(227,179,65,0.1); border-color: var(--accent-yellow); color: var(--accent-yellow); }
.subarray-box.maxs { background: rgba(86,211,100,0.1); border-color: var(--accent-green); color: var(--accent-green); }

/* ===== Animations ===== */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

.array-cell, .stack-cell, .node-box {
  animation: none;
}

.pulse {
  animation: pulse 0.5s ease;
}

@keyframes pulse {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.2); }
}

/* ═══════════════════════════════════════
   COMING SOON PAGES
═══════════════════════════════════════ */
#coming-soon-view {
  overflow-y: auto;
  height: 100%;
}
#coming-soon-view::-webkit-scrollbar { width: 6px; }
#coming-soon-view::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

.cs-hero {
  padding: 52px 40px 40px;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(22,27,34,0.8) 0%, transparent 100%);
}
.cs-hero-sm { padding: 36px 40px 32px; }

.cs-icon {
  font-size: 56px;
  width: 88px;
  height: 88px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 20px;
  margin-bottom: 20px;
  box-shadow: 0 0 40px -10px var(--pcolor, #79c0ff);
}

.cs-lc-badge {
  width: 80px;
  height: 80px;
  border-radius: 16px;
  background: linear-gradient(135deg, #f78166, #e3b341);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  font-weight: 900;
  color: #0d1117;
  margin-bottom: 20px;
}

.cs-title {
  font-size: 28px;
  font-weight: 800;
  margin-bottom: 10px;
  line-height: 1.2;
}
.cs-tagline {
  font-size: 15px;
  color: var(--text-secondary);
  margin-bottom: 8px;
}
.cs-desc {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.8;
  max-width: 600px;
  margin-bottom: 20px;
}

.cs-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 16px;
  background: rgba(227,179,65,0.1);
  border: 1px solid rgba(227,179,65,0.3);
  border-radius: 20px;
  font-size: 12px;
  font-weight: 700;
  color: var(--accent-yellow);
  letter-spacing: 0.3px;
}

/* Body layout */
.cs-body {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  padding: 36px 40px 60px;
  max-width: 1000px;
}
@media (max-width: 700px) { .cs-body { grid-template-columns: 1fr; } }

.cs-col-title {
  font-size: 13px;
  font-weight: 700;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 14px;
}

/* Topic cards */
.cs-topics { display: flex; flex-direction: column; gap: 8px; }
.cs-topic-card {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 10px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  transition: border-color 0.15s;
}
.cs-topic-card:hover { border-color: var(--accent-blue); }
.cst-icon { font-size: 18px; flex-shrink: 0; margin-top: 1px; }
.cst-name { font-size: 13px; font-weight: 600; color: var(--text-primary); margin-bottom: 2px; }
.cst-tag  { font-size: 11px; color: var(--text-secondary); }

/* Skills */
.cs-skills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
}
.cs-skill {
  padding: 5px 12px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 20px;
  font-size: 12px;
  color: var(--text-secondary);
}

/* Notify */
.cs-notify {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px;
}
.cs-notify h4 {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 12px;
}
.cs-notify-row { display: flex; gap: 8px; }
.cs-email {
  flex: 1;
  background: var(--bg-dark);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 13px;
  color: var(--text-primary);
  outline: none;
}
.cs-email:focus { border-color: var(--accent-blue); }
.cs-email::placeholder { color: var(--text-dim); }
.cs-notify-btn {
  padding: 8px 16px;
  background: var(--accent-blue);
  border: none;
  border-radius: 6px;
  color: #0d1117;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: opacity 0.15s;
  white-space: nowrap;
}
.cs-notify-btn:hover { opacity: 0.85; }

/* LC 75 / 150 category grid */
.cs-lc-body { padding: 36px 40px 60px; }
.cs-lc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 8px;
}
.cs-lc-cat {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 7px;
  font-size: 12px;
  transition: border-color 0.15s;
}
.cs-lc-cat:hover { border-color: var(--accent-blue); }
.cs-lc-cat-name  { color: var(--text-primary); font-weight: 500; }
.cs-lc-cat-count { color: var(--accent-blue); font-weight: 700; font-size: 11px; }

/* Welcome dim-fyi */
.dim-fyi { color: var(--text-secondary); font-weight: 400; }

/* LC list sidebar summary */
.lc-summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 14px;
  margin-bottom: 4px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
}
.lc-label { font-size: 11px; font-weight: 700; color: var(--accent-blue); letter-spacing: 0.05em; text-transform: uppercase; }
.lc-meta  { font-size: 11px; color: var(--text-secondary); }

/* AI Interview embed */
#ai-embed-view {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
}
#ai-embed-view.hidden { display: none; }
#ai-iframe {
  flex: 1;
  width: 100%;
  height: 100%;
  border: none;
  background: #09090e;
}

/* ── AI: Learning Paths ─────────────────────────────── */
#ai-learning-paths-view {
  padding: 40px 32px;
  max-width: 860px;
  margin: 0 auto;
}
.lp-hero { text-align: center; margin-bottom: 40px; }
.lp-hero-icon { font-size: 40px; margin-bottom: 12px; }
.lp-hero-title { font-size: 26px; font-weight: 700; color: var(--text-primary); margin: 0 0 8px; }
.lp-hero-sub { font-size: 14px; color: var(--text-secondary); margin: 0; }

.lp-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 20px; }

.lp-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  cursor: pointer;
  transition: border-color 0.2s, transform 0.15s, box-shadow 0.2s;
}
.lp-card:not(.lp-card-soon):hover {
  border-color: var(--accent-blue);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.3);
}
.lp-card-soon { cursor: default; opacity: 0.6; }

.lp-card-icon { font-size: 32px; }
.lp-card-body { flex: 1; }
.lp-card-title { font-size: 18px; font-weight: 700; color: var(--text-primary); margin: 0 0 8px; }
.lp-card-desc  { font-size: 13px; color: var(--text-secondary); line-height: 1.6; margin: 0 0 12px; }
.lp-card-tags  { display: flex; flex-wrap: wrap; gap: 6px; }
.lp-tag {
  font-size: 11px; font-weight: 600; padding: 3px 8px;
  border-radius: 20px; background: var(--bg-tertiary);
  color: var(--text-secondary); border: 1px solid var(--border);
}
.lp-card-footer { display: flex; align-items: center; justify-content: space-between; }
.lp-live-badge  { font-size: 11px; font-weight: 700; color: #56d364; }
.lp-soon-badge  { font-size: 12px; color: var(--text-secondary); }
.lp-start-btn {
  padding: 7px 16px; border-radius: 6px; border: none;
  background: var(--accent-blue); color: #fff;
  font-size: 12px; font-weight: 600; cursor: pointer;
  transition: opacity 0.15s;
}
.lp-start-btn:hover { opacity: 0.85; }

/* ── AI: Engineer embed ─────────────────────────────── */
#ai-embed-view {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
}
#ai-embed-view.hidden { display: none; }

.ai-embed-bar {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 0 20px;
  height: 44px;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.ai-back-btn {
  background: none; border: 1px solid var(--border); color: var(--text-secondary);
  padding: 4px 12px; border-radius: 6px; font-size: 12px; cursor: pointer;
  transition: border-color 0.15s, color 0.15s;
}
.ai-back-btn:hover { border-color: var(--accent-blue); color: var(--text-primary); }
.ai-embed-title { font-size: 13px; font-weight: 600; color: var(--text-primary); flex: 1; }
.ai-embed-live  { font-size: 11px; font-weight: 700; color: #56d364; }

#ai-iframe {
  flex: 1;
  width: 100%;
  border: none;
  background: #09090e;
}