:root {
  font-family: ui-monospace, 'SF Mono', Menlo, Monaco, 'Cascadia Mono',
    'Roboto Mono', Consolas, monospace;
  color-scheme: dark;
  --bg: #050507;
  --fg: #e5e5e5;
  --muted: #888;
  --dim: #555;
  --border: #1a1a1f;
  --border-hover: #2a2a33;
  --accent: #4ade80;
  --danger: #f87171;
  --warn: #facc15;
  --blue: #60a5fa;
  --panel: #0a0a10;
  --panel-lighter: #0d0d14;
  --editor-bg: #0b0b12;
  --code: #11111a;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; }

body {
  background: radial-gradient(ellipse at top, #0a0a14 0%, var(--bg) 70%);
  color: var(--fg);
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 1rem 1rem 0.75rem;
  gap: 0.85rem;
}

/* ---------- header ---------- */
header {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: 1rem;
  flex-wrap: wrap;
  flex-shrink: 0;
}

.brand h1 {
  font-size: clamp(1.6rem, 5vw, 2.1rem);
  font-weight: 600;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, #fff, #888);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.brand h1::before {
  content: '> ';
  color: var(--accent);
  -webkit-text-fill-color: var(--accent);
}
.home-link {
  text-decoration: none;
  display: inline-block;
  transition: opacity 0.15s;
}
.home-link:hover { opacity: 0.75; }
.tagline {
  color: var(--muted);
  font-size: 0.8rem;
  margin-top: 0.15rem;
}

.lang-tabs { display: flex; gap: 0.25rem; }
.lang-tab {
  font-family: inherit;
  font-size: 0.8rem;
  background: transparent;
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.45rem 1rem;
  cursor: pointer;
  transition: all 0.15s;
  text-transform: none;
  letter-spacing: 0;
  font-weight: 400;
}
.lang-tab:hover:not(:disabled) {
  color: var(--fg);
  border-color: var(--border-hover);
}
.lang-tab.active {
  color: var(--accent);
  border-color: var(--accent);
  background: rgba(74, 222, 128, 0.05);
}
.lang-tab:disabled { opacity: 0.4; cursor: not-allowed; }

/* ---------- layout ---------- */
.layout {
  flex: 1;
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 0.75rem;
  min-height: 0;
}

/* ---------- sidebar ---------- */
.sidebar {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  min-height: 0;
}
.sidebar-head {
  padding: 0.75rem 0.95rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.7rem;
  color: var(--dim);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #08080c;
  flex-shrink: 0;
}
.sidebar-head .progress {
  color: var(--accent);
  font-weight: 600;
}
.lesson-list {
  list-style: none;
  padding: 0.35rem 0;
  margin: 0;
  overflow-y: auto;
  flex: 1;
}
.lesson-list li {
  padding: 0.55rem 0.95rem;
  font-size: 0.82rem;
  cursor: pointer;
  color: var(--muted);
  border-left: 2px solid transparent;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: all 0.12s;
}
.lesson-list li:hover {
  color: var(--fg);
  background: rgba(255, 255, 255, 0.02);
}
.lesson-list li.active {
  color: var(--accent);
  border-left-color: var(--accent);
  background: rgba(74, 222, 128, 0.05);
}
.lesson-list li .check {
  width: 14px;
  flex-shrink: 0;
  text-align: center;
  color: var(--dim);
  font-size: 0.75rem;
}
.lesson-list li.done .check { color: var(--accent); }
.lesson-list li.done {
  text-decoration: none;
}
.lesson-list li .title { flex: 1; }

.sidebar-foot {
  padding: 0.55rem 0.75rem;
  border-top: 1px solid var(--border);
  flex-shrink: 0;
}

/* ---------- workspace ---------- */
.workspace {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  min-height: 0;
  min-width: 0;
}

/* ---------- lesson panel ---------- */
.lesson-panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  max-height: 42%;
  flex-shrink: 0;
}
.lesson-panel[hidden] { display: none; }

.lesson-head {
  padding: 0.65rem 0.95rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  background: #08080c;
  flex-shrink: 0;
}
.lesson-meta {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  min-width: 0;
}
.lesson-index {
  font-size: 0.7rem;
  color: var(--dim);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.lesson-title {
  font-size: 0.95rem;
  color: var(--fg);
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.lesson-actions {
  display: flex;
  gap: 0.4rem;
  flex-shrink: 0;
}

.lesson-content {
  overflow-y: auto;
  padding: 1rem 1.25rem 1.25rem;
  font-family: -apple-system, system-ui, 'Segoe UI', sans-serif;
  font-size: 0.88rem;
  line-height: 1.65;
  color: var(--fg);
}

.lesson-content h1,
.lesson-content h2,
.lesson-content h3 {
  margin: 1.2em 0 0.4em;
  line-height: 1.25;
  color: #fff;
  font-weight: 600;
}
.lesson-content h1:first-child,
.lesson-content h2:first-child { margin-top: 0; }
.lesson-content h1 { font-size: 1.35rem; }
.lesson-content h2 { font-size: 1.1rem; color: var(--accent); }
.lesson-content h3 { font-size: 0.98rem; }
.lesson-content p { margin: 0.55em 0; }
.lesson-content ul, .lesson-content ol {
  margin: 0.55em 0 0.55em 1.4em;
}
.lesson-content li { margin: 0.18em 0; }
.lesson-content strong { color: #fff; }

.lesson-content code {
  font-family: ui-monospace, Menlo, monospace;
  background: var(--code);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 0.06em 0.35em;
  font-size: 0.85em;
  color: var(--accent);
}
.lesson-content pre {
  background: var(--code);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.8em 1em;
  overflow-x: auto;
  margin: 0.7em 0;
}
.lesson-content pre code {
  background: transparent;
  border: none;
  padding: 0;
  font-size: 0.82rem;
  color: var(--fg);
}

/* ---------- editor row ---------- */
.editor-row {
  flex: 1;
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 0.75rem;
  min-height: 0;
}

.pane {
  display: flex;
  flex-direction: column;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  min-height: 0;
}

.pane-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.55rem 0.85rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.7rem;
  color: var(--dim);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  background: #08080c;
  flex-shrink: 0;
}

.pane-actions {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.pane-header .hint,
.pane-header .meta {
  font-size: 0.68rem;
  color: var(--muted);
  text-transform: none;
  letter-spacing: 0;
}

.pane-header .meta.loading { color: var(--warn); }
.pane-header .meta.ready { color: var(--accent); }
.pane-header .meta.error { color: var(--danger); }

/* ---------- buttons ---------- */
button {
  font-family: inherit;
  font-size: 0.72rem;
  background: var(--accent);
  color: #061a0c;
  border: 1px solid var(--accent);
  border-radius: 4px;
  padding: 0.35rem 0.85rem;
  cursor: pointer;
  font-weight: 600;
  transition: opacity 0.15s;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
button:hover:not(:disabled) { opacity: 0.85; }
button:disabled { opacity: 0.4; cursor: not-allowed; }

button.ghost {
  background: transparent;
  color: var(--muted);
  border: 1px solid var(--border);
  font-weight: 400;
  text-transform: none;
  letter-spacing: 0;
}
button.ghost:hover:not(:disabled) {
  color: var(--fg);
  border-color: var(--border-hover);
  opacity: 1;
}
button.ghost.small {
  font-size: 0.68rem;
  padding: 0.3rem 0.65rem;
  width: 100%;
}
button.ghost.icon {
  padding: 0.2rem 0.55rem;
  font-size: 1rem;
  line-height: 1;
}

/* ---------- editor + output ---------- */
#editor {
  flex: 1;
  min-height: 0;
  font-family: inherit !important;
}

.output {
  flex: 1;
  overflow-y: auto;
  padding: 1rem 1.1rem;
  font-size: 0.85rem;
  line-height: 1.6;
  white-space: pre-wrap;
  word-break: break-word;
  color: var(--fg);
  margin: 0;
}

.output .run-sep {
  color: var(--dim);
  border-top: 1px dashed var(--border);
  margin: 0.5rem 0;
  padding-top: 0.5rem;
  display: block;
  font-size: 0.75rem;
}
.output .run-sep:first-child {
  border-top: none;
  margin-top: 0;
  padding-top: 0;
}

.output .err { color: var(--danger); }
.output .result { color: var(--accent); }
.output .info { color: var(--muted); font-style: italic; }

/* SQL result tables */
.sql-result {
  margin: 0.4rem 0 0.8rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: auto;
  max-width: 100%;
}
.sql-result table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.8rem;
  font-family: ui-monospace, Menlo, monospace;
}
.sql-result th {
  background: #08080c;
  color: var(--accent);
  text-align: left;
  padding: 0.45rem 0.75rem;
  border-bottom: 1px solid var(--border);
  font-weight: 600;
  position: sticky;
  top: 0;
  white-space: nowrap;
}
.sql-result td {
  padding: 0.4rem 0.75rem;
  border-bottom: 1px solid var(--border);
  color: var(--fg);
  white-space: nowrap;
}
.sql-result tr:last-child td { border-bottom: none; }
.sql-result tr:nth-child(even) td { background: rgba(255, 255, 255, 0.015); }
.sql-result td.null { color: var(--dim); font-style: italic; }
.sql-meta {
  font-size: 0.72rem;
  color: var(--muted);
  margin-bottom: 0.25rem;
  font-style: italic;
}

/* Ace editor overrides */
.ace_editor {
  background: var(--editor-bg) !important;
  font-family: ui-monospace, 'SF Mono', Menlo, monospace !important;
  font-size: 13px !important;
}
.ace_gutter {
  background: #08080c !important;
  color: var(--dim) !important;
}

footer {
  text-align: center;
  padding: 0.15rem 0 0.25rem;
  flex-shrink: 0;
}
footer a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.8rem;
}
footer a:hover { color: var(--accent); }

/* ---------- responsive ---------- */
@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    max-height: 180px;
  }
  .editor-row { grid-template-columns: 1fr; }
  .pane { min-height: 35vh; }
  .lesson-panel { max-height: 50vh; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation: none !important;
    transition: none !important;
  }
}