/* ==========================================================================
   ROOT / THEME
   ========================================================================== */
:root {
  --bg-plasma: #020205;
  --glass-base: rgba(255, 255, 255, 0.04);
  --glass-surface: rgba(4, 6, 14, 0.75);
  --glass-border: rgba(255, 255, 255, 0.18);

  --accent-neon-cyan: #00f5ff;
  --accent-neon-magenta: #ff0055;
  --text-ultra-bright: #ffffff;
  --text-neon-glow: #00ffaa;
  --text-secondary: #a2a9bc;
  --text-dark: #6b7180;

  --font-future: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --sidebar-width: 340px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  letter-spacing: -0.01em;
}

html, body {
  width: 100%;
  min-height: 100%;
  background-color: var(--bg-plasma);
  color: var(--text-ultra-bright);
  font-family: var(--font-future);
  -webkit-font-smoothing: antialiased;
}

body {
  display: flex;
  flex-direction: column;
  height: 100vh;
  overflow: hidden;
  position: relative;
}

body::before {
  content: "";
  position: fixed;
  top: -50%; left: -50%; right: -50%; bottom: -50%;
  z-index: -1;
  background:
    radial-gradient(circle at 20% 20%, rgba(0, 245, 255, 0.16) 0%, transparent 35%),
    radial-gradient(circle at 80% 80%, rgba(255, 0, 85, 0.18) 0%, transparent 40%),
    radial-gradient(circle at 50% 50%, #020205 0%, #060711 100%);
  animation: fluidMesh 24s ease infinite alternate;
}

@keyframes fluidMesh {
  0% { transform: rotate(0deg) scale(1); }
  100% { transform: rotate(10deg) scale(1.08); }
}

a { color: inherit; text-decoration: none; }
button { font-family: var(--font-future); }

/* ==========================================================================
   HEADER
   ========================================================================== */
.app-header {
  background: linear-gradient(180deg, rgba(4, 6, 14, 0.85) 0%, rgba(2, 2, 5, 0.4) 100%);
  border-bottom: 1px solid var(--glass-border);
  backdrop-filter: blur(25px) saturate(180%);
  -webkit-backdrop-filter: blur(25px) saturate(180%);
  padding: 16px 28px;
  flex-shrink: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 18px;
}

.menu-toggle {
  background: var(--glass-base);
  border: 1px solid var(--glass-border);
  color: var(--text-ultra-bright);
  width: 42px;
  height: 42px;
  border-radius: 12px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: all 0.25s ease;
}
.menu-toggle:hover { border-color: var(--accent-neon-cyan); box-shadow: 0 0 15px rgba(0,245,255,0.25); }
.menu-toggle svg { width: 20px; height: 20px; stroke: currentColor; }

.header-titles { display: flex; flex-direction: column; gap: 2px; min-width: 0; }

.app-header h1 {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  background: linear-gradient(90deg, #ffffff 0%, var(--accent-neon-cyan) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.subtitle {
  color: var(--accent-neon-magenta);
  font-size: 0.7rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  text-shadow: 0 0 12px rgba(255, 0, 85, 0.6);
}

.header-progress {
  margin-left: auto;
  font-size: 0.75rem;
  color: var(--text-dark);
  font-weight: 600;
  letter-spacing: 0.08em;
  white-space: nowrap;
  padding-left: 12px;
}

/* ==========================================================================
   LAYOUT SHELL
   ========================================================================== */
.app-body {
  flex: 1;
  display: flex;
  min-height: 0;
  position: relative;
}

/* ==========================================================================
   SIDEBAR
   ========================================================================== */
.topic-sidebar {
  width: var(--sidebar-width);
  flex-shrink: 0;
  background: rgba(3, 4, 10, 0.82);
  border-right: 1px solid var(--glass-border);
  backdrop-filter: blur(30px) saturate(200%);
  -webkit-backdrop-filter: blur(30px) saturate(200%);
  display: flex;
  flex-direction: column;
  min-height: 0;
  transition: margin-left 0.35s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.35s ease;
  z-index: 90;
}

.topic-sidebar.collapsed {
  margin-left: calc(-1 * var(--sidebar-width));
}

.sidebar-search-wrap {
  padding: 18px 18px 12px 18px;
  flex-shrink: 0;
  border-bottom: 1px solid rgba(255,255,255,0.06);
}

.sidebar-search-wrap input {
  width: 100%;
  background: var(--glass-base);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  padding: 10px 14px;
  color: var(--text-ultra-bright);
  font-size: 0.88rem;
  font-family: var(--font-future);
  outline: none;
  transition: border-color 0.25s ease, box-shadow 0.25s ease;
}
.sidebar-search-wrap input::placeholder { color: var(--text-dark); }
.sidebar-search-wrap input:focus {
  border-color: var(--accent-neon-cyan);
  box-shadow: 0 0 15px rgba(0, 245, 255, 0.15);
}

.sidebar-scroll {
  overflow-y: auto;
  padding: 14px 14px 30px 14px;
  flex: 1;
}
.sidebar-scroll::-webkit-scrollbar { width: 8px; }
.sidebar-scroll::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 8px; }
.sidebar-scroll::-webkit-scrollbar-track { background: transparent; }

/* Tree */
.tree-node { margin-bottom: 4px; }

.tree-node > summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 10px;
  border-radius: 10px;
  color: var(--text-secondary);
  font-size: 0.86rem;
  font-weight: 600;
  transition: all 0.2s ease;
}
.tree-node > summary::-webkit-details-marker { display: none; }
.tree-node > summary:hover { background: rgba(255,255,255,0.06); color: var(--text-ultra-bright); }

.tree-node > summary .chevron {
  width: 14px; height: 14px; flex-shrink: 0;
  transition: transform 0.25s ease;
  stroke: var(--text-dark);
}
.tree-node[open] > summary .chevron { transform: rotate(90deg); stroke: var(--accent-neon-cyan); }

.tree-node .node-label { flex: 1; min-width: 0; overflow-wrap: anywhere; }

.tree-children { padding-left: 16px; border-left: 1px solid rgba(255,255,255,0.06); margin-left: 16px; margin-top: 2px; }

.depth-1 > summary { font-size: 0.92rem; font-weight: 700; color: var(--text-ultra-bright); }
.depth-1 { margin-bottom: 8px; }

.leaf-btn {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 10px;
  border-radius: 10px;
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-secondary);
  font-size: 0.84rem;
  text-align: left;
  cursor: pointer;
  transition: all 0.2s ease;
  margin-bottom: 2px;
}
.leaf-btn::before {
  content: "";
  width: 5px; height: 5px; border-radius: 50%;
  background: var(--text-dark);
  flex-shrink: 0;
  transition: all 0.2s ease;
}
.leaf-btn:hover { background: rgba(255,255,255,0.06); color: var(--text-ultra-bright); }
.leaf-btn:hover::before { background: var(--accent-neon-cyan); }

.leaf-btn.active {
  color: #ffffff;
  background: linear-gradient(135deg, rgba(0, 245, 255, 0.2) 0%, rgba(255, 0, 85, 0.08) 100%);
  border-color: rgba(0, 245, 255, 0.4);
  font-weight: 700;
  box-shadow: 0 0 18px rgba(0, 245, 255, 0.15);
}
.leaf-btn.active::before { background: var(--accent-neon-cyan); box-shadow: 0 0 8px var(--accent-neon-cyan); }

.leaf-btn.has-content::after {
  content: "";
}

.tree-empty-msg {
  color: var(--text-dark);
  font-size: 0.82rem;
  padding: 20px 10px;
  text-align: center;
}

.search-highlight {
  background: rgba(255, 0, 85, 0.25);
  color: #fff;
  border-radius: 3px;
  padding: 0 2px;
}

/* ==========================================================================
   CONTENT VIEWPORT
   ========================================================================== */
.content-viewport {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  padding: 30px 40px;
}

.breadcrumb {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  font-size: 0.78rem;
  color: var(--text-dark);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 700;
  margin-bottom: 18px;
  flex-shrink: 0;
  max-width: 880px;
  margin-left: auto;
  margin-right: auto;
  width: 100%;
}
.breadcrumb .crumb { cursor: pointer; transition: color 0.2s ease; }
.breadcrumb .crumb:hover { color: var(--accent-neon-cyan); }
.breadcrumb .crumb.current { color: var(--text-secondary); cursor: default; }
.breadcrumb .sep { color: rgba(255,255,255,0.15); }

.content-card-viewport {
  flex: 1;
  overflow-y: auto;
  max-width: 880px;
  margin: 0 auto;
  width: 100%;
  padding-bottom: 20px;
}
.content-card-viewport::-webkit-scrollbar { width: 8px; }
.content-card-viewport::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 8px; }

.content-page-view {
  display: flex;
  flex-direction: column;
  opacity: 1;
  transform: translateY(0px);
  transition: opacity 0.3s ease, transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}
.content-page-view.fade-out { opacity: 0; transform: translateY(10px); }

.content-card-viewport h2 {
  font-size: 2rem;
  font-weight: 800;
  background: linear-gradient(135deg, #ffffff 40%, var(--accent-neon-cyan) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
  line-height: 1.2;
}

.summary-text {
  font-size: 1.08rem;
  color: var(--text-secondary);
  line-height: 1.55;
  margin-bottom: 30px;
  max-width: 780px;
}

.blocks-container-area { display: flex; flex-direction: column; gap: 28px; }

.section-block h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-neon-glow);
  text-shadow: 0 0 10px rgba(0, 255, 170, 0.25);
}
.section-block p { color: var(--text-secondary); font-size: 1rem; line-height: 1.65; }
.section-block ul { list-style-type: none; display: flex; flex-direction: column; gap: 12px; }
.section-block li {
  font-size: 1rem; line-height: 1.5; color: var(--text-secondary);
  position: relative; padding-left: 26px;
}
.section-block li strong { color: var(--text-ultra-bright); font-weight: 600; }
.section-block li::before {
  content: ""; position: absolute; left: 4px; top: 8px;
  width: 7px; height: 7px; border-radius: 50%;
  background: var(--accent-neon-magenta);
  box-shadow: 0 0 10px var(--accent-neon-magenta);
}

.table-responsive {
  width: 100%; margin-top: 6px;
  background: var(--glass-surface);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
  border-radius: 16px; overflow: hidden auto;
  box-shadow: 0 20px 40px rgba(0,0,0,0.4);
}
table { width: 100%; border-collapse: collapse; text-align: left; font-size: 0.9rem; }
th {
  color: #ffffff; background: rgba(255, 255, 255, 0.05);
  font-weight: 700; padding: 13px 18px;
  border-bottom: 1px solid var(--glass-border);
  text-transform: uppercase; letter-spacing: 0.05em;
  white-space: nowrap;
}
td { padding: 13px 18px; border-bottom: 1px solid rgba(255, 255, 255, 0.06); color: var(--text-secondary); line-height: 1.5; }
tr:last-child td { border-bottom: none; }

/* Hub / overview grid (non-leaf nodes) */
.hub-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 16px;
}
.hub-card {
  background: var(--glass-base);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
  padding: 18px 18px;
  cursor: pointer;
  text-align: left;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.hub-card:hover {
  border-color: var(--accent-neon-cyan);
  background: rgba(255,255,255,0.07);
  transform: translateY(-3px);
  box-shadow: 0 15px 30px rgba(0, 245, 255, 0.1);
}
.hub-card .hub-card-index {
  font-size: 0.7rem; font-weight: 800; color: var(--accent-neon-cyan);
  letter-spacing: 0.1em; text-transform: uppercase;
}
.hub-card .hub-card-title { font-size: 1rem; font-weight: 700; color: var(--text-ultra-bright); line-height: 1.35; }
.hub-card .hub-card-meta { font-size: 0.78rem; color: var(--text-dark); }

/* Placeholder for topics without content yet */
.content-placeholder {
  border: 1px dashed rgba(255,255,255,0.18);
  border-radius: 16px;
  padding: 26px;
  color: var(--text-dark);
  font-size: 0.92rem;
  line-height: 1.6;
}
.content-placeholder code {
  background: rgba(255,255,255,0.06);
  padding: 2px 6px;
  border-radius: 6px;
  color: var(--accent-neon-cyan);
  font-size: 0.85em;
}

/* ==========================================================================
   PAGINATION FOOTER
   ========================================================================== */
.pagination-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 880px;
  margin: 0 auto;
  width: 100%;
  padding-top: 18px;
  margin-top: 12px;
  border-top: 1px solid var(--glass-border);
  flex-shrink: 0;
}

.page-indicator {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-dark);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.nav-cluster { display: flex; gap: 16px; }

.nav-btn {
  background: var(--glass-base);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(15px); -webkit-backdrop-filter: blur(15px);
  color: var(--text-ultra-bright);
  padding: 10px 22px;
  border-radius: 12px;
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  cursor: pointer;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}
.nav-btn:hover:not(:disabled) {
  background: rgba(255, 255, 255, 0.08);
  border-color: var(--accent-neon-cyan);
  box-shadow: 0 0 20px rgba(0, 245, 255, 0.2);
  transform: translateY(-2px);
}
.nav-btn:disabled {
  border-color: rgba(255, 255, 255, 0.02);
  background: rgba(255, 255, 255, 0.01);
  color: var(--text-dark);
  cursor: not-allowed;
}

/* ==========================================================================
   LOADING / ERROR STATES
   ========================================================================== */
.boot-screen {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 14px;
  text-align: center;
  padding: 40px;
}
.boot-screen h2 { font-size: 1.3rem; color: var(--text-ultra-bright); }
.boot-screen p { color: var(--text-secondary); max-width: 520px; line-height: 1.6; font-size: 0.95rem; }
.boot-screen code {
  background: rgba(255,255,255,0.06);
  padding: 3px 8px;
  border-radius: 6px;
  color: var(--accent-neon-cyan);
  font-size: 0.88em;
  display: inline-block;
  margin: 3px 0;
}
.boot-retry {
  margin-top: 8px;
  background: var(--glass-base);
  border: 1px solid var(--accent-neon-cyan);
  color: var(--text-ultra-bright);
  padding: 10px 26px;
  border-radius: 12px;
  font-weight: 700;
  cursor: pointer;
}

/* ==========================================================================
   RESPONSIVE
   ========================================================================== */
@media (max-width: 900px) {
  :root { --sidebar-width: 86vw; }
  .topic-sidebar { position: fixed; top: 0; bottom: 0; left: 0; height: 100%; box-shadow: 40px 0 60px rgba(0,0,0,0.5); }
  .topic-sidebar.collapsed { margin-left: calc(-1 * var(--sidebar-width)); }
  .content-viewport { padding: 24px 18px; }
  .header-progress { display: none; }
}

.sidebar-scrim {
  display: none;
}
@media (max-width: 900px) {
  .sidebar-scrim.show {
    display: block;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    z-index: 80;
  }
}