:root {
  --bg: #0b0f16;
  --panel: #0f1623;
  --muted: #8aa0b5;
  --text: #e7eef7;
  --accent: #6ee7ff;
  --accent2: #a78bfa;
  --green: #34d399;
  --orange: #fbbf24;
  --red: #f87171;
  --line: #26364a;
  --surface: rgba(15, 22, 35, 0.7);
  --radius: 14px;
  --radius-lg: 18px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: linear-gradient(180deg, #070a10 0%, #0b0f16 40%, #070a10 100%);
  color: var(--text);
  min-height: 100vh;
}

/* ===== Header ===== */

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 20px;
  border-bottom: 1px solid #111a28;
  background: rgba(10, 14, 22, 0.75);
  backdrop-filter: blur(12px);
  position: sticky;
  top: 0;
  z-index: 10;
}

.brand { display: flex; align-items: center; gap: 12px; }

.logo {
  width: 36px; height: 36px;
  border-radius: 12px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, rgba(110, 231, 255, 0.2), rgba(110, 231, 255, 0.05));
  border: 1px solid rgba(110, 231, 255, 0.25);
  font-weight: 800;
  letter-spacing: -0.03em;
  color: var(--accent);
  font-size: 16px;
}

.title { font-weight: 800; letter-spacing: -0.02em; font-size: 18px; }
.subtitle { font-size: 12px; color: var(--muted); margin-top: 2px; }

.header-right { display: flex; align-items: center; gap: 12px; }

.kbd-hint {
  font-size: 11px;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 4px;
}

kbd {
  display: inline-block;
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid #2a3a52;
  background: rgba(20, 30, 50, 0.6);
  font-family: inherit;
  font-size: 10px;
  color: var(--text);
}

.status {
  font-size: 12px;
  color: var(--muted);
  padding: 5px 12px;
  border: 1px solid #1b2a40;
  border-radius: 999px;
  white-space: nowrap;
  transition: all 0.3s;
}

/* ===== Tabs ===== */

main { padding: 16px 20px; }

.tabs {
  display: flex;
  gap: 6px;
  margin-bottom: 16px;
  overflow-x: auto;
  padding-bottom: 12px;
  border-bottom: 1px solid #162338;
  scrollbar-width: none;
}
.tabs::-webkit-scrollbar { display: none; }

.tab {
  flex: none;
  cursor: pointer;
  border: 1px solid #1b2a40;
  background: rgba(15, 22, 35, 0.5);
  color: var(--muted);
  border-radius: 10px 10px 0 0;
  padding: 8px 18px;
  font-weight: 600;
  font-size: 13px;
  transition: all 0.2s;
  white-space: nowrap;
}
.tab:hover { border-color: rgba(110, 231, 255, 0.25); color: var(--text); }
.tab.active {
  border-color: rgba(110, 231, 255, 0.4);
  background: linear-gradient(135deg, rgba(110, 231, 255, 0.15), rgba(110, 231, 255, 0.05));
  color: var(--accent);
  border-bottom-color: transparent;
}

.demo-content { display: none; }

.demo-content.active { display: block; }

/* ===== Panel ===== */

.panel {
  background: var(--surface);
  border: 1px solid #162338;
  border-radius: var(--radius-lg);
  padding: 18px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}
.panel.full-width { max-width: 1200px; }

.panel h2 { margin: 0 0 6px 0; letter-spacing: -0.02em; font-size: 20px; }
.lead { color: var(--muted); margin: 0 0 14px 0; line-height: 1.4; font-size: 14px; }
.lead code {
  background: rgba(110, 231, 255, 0.1);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--accent);
  font-size: 13px;
}

/* ===== Controls ===== */

.controls {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin: 10px 0 14px 0;
}

label {
  display: flex;
  flex-direction: column;
  gap: 5px;
  font-size: 12px;
  color: var(--muted);
  border: 1px solid #152235;
  border-radius: var(--radius);
  padding: 10px;
  background: rgba(10, 15, 24, 0.55);
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
}
.val { font-size: 13px; color: var(--text); font-weight: 600; }

/* ===== Buttons ===== */

.buttons {
  grid-column: 1 / -1;
  display: flex;
  gap: 10px;
}

button {
  cursor: pointer;
  border: 1px solid #1b2a40;
  background: rgba(15, 22, 35, 0.6);
  color: var(--text);
  border-radius: var(--radius);
  padding: 10px 16px;
  font-weight: 600;
  font-size: 13px;
  transition: all 0.2s;
}
button:hover { border-color: rgba(110, 231, 255, 0.3); background: rgba(110, 231, 255, 0.08); }
button:active { transform: scale(0.97); }

.btn-run {
  border: 1px solid rgba(110, 231, 255, 0.3);
  background: linear-gradient(135deg, rgba(110, 231, 255, 0.2), rgba(110, 231, 255, 0.06));
  color: var(--accent);
  font-weight: 700;
}
.btn-run:hover { border-color: rgba(110, 231, 255, 0.5); background: linear-gradient(135deg, rgba(110, 231, 255, 0.3), rgba(110, 231, 255, 0.1)); }

.btn-sm {
  padding: 6px 12px;
  font-size: 12px;
  border-radius: 8px;
}

/* ===== Stats cards ===== */

.stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 10px;
}

.stat {
  border: 1px solid #152235;
  border-radius: var(--radius);
  padding: 10px;
  background: rgba(10, 15, 24, 0.55);
}
.k { font-size: 11px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.04em; }
.v { font-size: 20px; font-weight: 800; margin-top: 4px; letter-spacing: -0.02em; }

/* ===== Output / Console ===== */

.out {
  margin: 8px 0 0 0;
  max-height: 120px;
  overflow: auto;
  border-radius: 10px;
  background: rgba(0, 0, 0, 0.3);
  padding: 10px;
  font-size: 12px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  border: 1px solid rgba(255, 255, 255, 0.06);
  color: var(--text);
  line-height: 1.5;
  white-space: pre-wrap;
  word-break: break-word;
}
.out.tall { max-height: 260px; }

/* ===== Code editor ===== */

.codebox { margin-top: 14px; }
.codebox summary {
  cursor: pointer;
  color: var(--muted);
  font-weight: 700;
  font-size: 13px;
  margin-bottom: 8px;
}

textarea {
  width: 100%;
  min-height: 220px;
  border-radius: 12px;
  border: 1px solid #1b2a40;
  background: rgba(0, 0, 0, 0.3);
  color: var(--text);
  padding: 14px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 13px;
  line-height: 1.45;
  resize: vertical;
  tab-size: 2;
  transition: border-color 0.2s;
}
textarea:focus {
  outline: none;
  border-color: rgba(110, 231, 255, 0.35);
  box-shadow: 0 0 0 3px rgba(110, 231, 255, 0.08);
}

.hint { margin-top: 8px; font-size: 12px; color: var(--muted); }
.hint kbd { margin: 0 2px; }

/* ===== Viz ===== */

.viz {
  background: var(--surface);
  border: 1px solid #162338;
  border-radius: var(--radius-lg);
  padding: 14px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
  overflow: hidden;
}
.viz.compact { margin-top: 12px; }
.viz.wide { flex: 1; }

.viz svg {
  width: 100%;
  height: auto;
  border-radius: 10px;
  background: rgba(0, 0, 0, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.04);
}

.foot { margin-top: 8px; color: var(--muted); font-size: 12px; }

/* ===== Layouts ===== */

/* Regression: side-by-side panel + chart */
#demo-regression.active {
  display: grid;
  grid-template-columns: 440px 1fr;
  gap: 16px;
}

/* Split layout for stats, dataframe, strings */
.split-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 14px;
}

/* Time series layout */
.ts-layout {
  display: flex;
  gap: 16px;
  margin-top: 14px;
}
.ts-stats {
  min-width: 180px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.ts-stat-card {
  border: 1px solid #152235;
  border-radius: var(--radius);
  padding: 10px 12px;
  background: rgba(10, 15, 24, 0.55);
}
.ts-stat-card .k { font-size: 10px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.05em; }
.ts-stat-card .v { font-size: 18px; font-weight: 700; margin-top: 2px; }

/* ===== Playground ===== */

.playground-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid #162338;
  border-radius: var(--radius-lg);
  overflow: hidden;
  min-height: 520px;
  background: var(--surface);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.play-editor {
  display: flex;
  flex-direction: column;
  border-right: 1px solid #162338;
}

.editor-header, .output-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  border-bottom: 1px solid #162338;
  background: rgba(10, 14, 20, 0.5);
}

.editor-title {
  font-weight: 700;
  font-size: 13px;
  color: var(--muted);
}
.editor-actions { display: flex; gap: 8px; }

.editor-wrap { flex: 1; display: flex; }
.editor-wrap textarea {
  flex: 1;
  border: none;
  border-radius: 0;
  min-height: unset;
  resize: none;
  padding: 16px;
  background: transparent;
}
.editor-wrap textarea:focus {
  box-shadow: none;
  border: none;
}

.play-output {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.output-header {
  gap: 0;
  justify-content: flex-start;
}

.output-tab {
  padding: 4px 14px;
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  cursor: pointer;
  border-radius: 6px;
  transition: all 0.2s;
}
.output-tab:hover { color: var(--text); }
.output-tab.active {
  color: var(--accent);
  background: rgba(110, 231, 255, 0.1);
}

.exec-time {
  margin-left: auto;
  font-size: 11px;
  color: var(--muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}

.play-console {
  display: none;
  flex: 1;
  margin: 0;
  padding: 16px;
  overflow: auto;
  font-size: 13px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  line-height: 1.5;
  color: var(--text);
  white-space: pre-wrap;
  word-break: break-word;
  background: transparent;
  border: none;
}
.play-console.active { display: block; }
.play-console.error { color: var(--red); }

/* ===== Data Frame Table ===== */

.df-table-wrap {
  margin-top: 12px;
  overflow-x: auto;
  border-radius: var(--radius);
  border: 1px solid #152235;
}

.df-table-wrap table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
}
.df-table-wrap th {
  text-align: left;
  padding: 8px 12px;
  background: rgba(110, 231, 255, 0.08);
  color: var(--accent);
  font-weight: 700;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  border-bottom: 1px solid #1b2a40;
}
.df-table-wrap td {
  padding: 7px 12px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.04);
  color: var(--text);
}
.df-table-wrap tr:hover td {
  background: rgba(110, 231, 255, 0.04);
}
.df-table-wrap .bool-true { color: var(--green); font-weight: 600; }
.df-table-wrap .bool-false { color: var(--red); font-weight: 600; }
.df-table-wrap .num { color: var(--orange); font-family: ui-monospace, monospace; }

/* ===== Footer ===== */

footer {
  padding: 16px 20px 24px 20px;
  color: var(--muted);
  font-size: 12px;
  text-align: center;
}
footer a { text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* ===== Tooltip ===== */

.tooltip {
  position: fixed;
  pointer-events: none;
  opacity: 0;
  padding: 8px 12px;
  border-radius: 10px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  background: rgba(10, 14, 22, 0.85);
  backdrop-filter: blur(10px);
  font: 12px ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  color: white;
  transition: opacity 0.15s;
  z-index: 100;
  line-height: 1.5;
}

/* ===== Responsive ===== */

@media (max-width: 1100px) {
  #demo-regression.active { grid-template-columns: 1fr; }
  .split-layout { grid-template-columns: 1fr; }
  .playground-layout { grid-template-columns: 1fr; }
  .play-editor { border-right: none; border-bottom: 1px solid #162338; }
  .editor-wrap textarea { min-height: 300px; }
  .ts-layout { flex-direction: column; }
}

@media (max-width: 640px) {
  header { flex-direction: column; gap: 8px; }
  .kbd-hint { display: none; }
  .tabs { gap: 4px; }
  .tab { padding: 6px 12px; font-size: 12px; }
  .controls { grid-template-columns: 1fr; }
  main { padding: 10px 12px; }
}

/* ===== Animations ===== */

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

.demo-content.active {
  animation: fadeIn 0.25s ease-out;
}

.stat .v, .ts-stat-card .v {
  transition: all 0.3s;
}