:root {
  color-scheme: light dark;

  /* Green theme */
  --accent: #22c55e;        /* green */
  --accent-strong: #16a34a; /* darker green */
  --accent-wash: rgba(34, 197, 94, 0.12);

  /* Light defaults */
  --bg: #f7f7f8;
  --fg: #0f172a;
  --muted: rgba(15, 23, 42, 0.70);
  --card-bg: rgba(255, 255, 255, 0.85);
  --border: rgba(15, 23, 42, 0.12);
  --hover: rgba(15, 23, 42, 0.05);
  --topbar-bg: rgba(247, 247, 248, 0.92);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b0f14;
    --fg: rgba(255, 255, 255, 0.92);
    --muted: rgba(255, 255, 255, 0.68);
    --card-bg: rgba(255, 255, 255, 0.06);
    --border: rgba(255, 255, 255, 0.14);
    --hover: rgba(255, 255, 255, 0.06);
    --topbar-bg: rgba(11, 15, 20, 0.92);
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial;
  background: var(--bg);
  color: var(--fg);
}

.container { max-width: 1000px; margin: 0 auto; padding: 24px; }

.card {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  background: var(--card-bg);
}

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

input, button {
  font: inherit;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--fg);
}

button { cursor: pointer; }

a { color: inherit; }
.small { color: var(--muted); font-size: 13px; }
.list { display: grid; gap: 10px; }

.item {
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border);
  text-decoration: none;
  display: block;
}

.item:hover { background: var(--accent-wash); border-color: rgba(34, 197, 94, 0.35); }

/* Topbar + layout */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 16px;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: var(--topbar-bg);
  backdrop-filter: blur(10px);
  z-index: 10;
}

.topbar__title { font-weight: 700; letter-spacing: 0.2px; }

.layout {
  display: grid;
  grid-template-columns: 320px 1fr;
  min-height: calc(100vh - 56px);
}

@media (max-width: 900px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar { border-right: none; border-bottom: 1px solid var(--border); }
}

.sidebar { border-right: 1px solid var(--border); padding: 12px; }
.sidebar__header { padding: 6px 6px 10px 6px; }
.content { padding: 16px; }
.muted { color: var(--muted); }

/* Buttons */
.btn {
  border: 1px solid rgba(34, 197, 94, 0.35);
  background: rgba(34, 197, 94, 0.10);
  color: var(--fg);
  padding: 8px 10px;
  border-radius: 10px;
  cursor: pointer;
}

.btn:hover { background: rgba(34, 197, 94, 0.16); }

.btn--ghost {
  background: transparent;
  border-color: var(--border);
}

.btn--ghost:hover { background: var(--hover); }

/* Pills + tree */
.pill {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  border-radius: 999px;
  font-size: 12px;
  color: var(--muted);
  border: 1px solid var(--border);
}

.pill--subtle { opacity: 0.85; }

.tree { display: grid; gap: 8px; }

.tree__node {
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
  background: var(--card-bg);
}

.tree__summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 10px 12px;
}

.tree__summary::-webkit-details-marker { display: none; }

.tree__summary:hover {
  background: var(--accent-wash);
}

.tree__title { font-weight: 600; }

.tree__children {
  padding: 6px 10px 10px 10px;
  display: grid;
  gap: 6px;
}

.tree__videos { padding-top: 4px; }

.tree__link {
  display: block;
  padding: 8px 10px;
  border-radius: 10px;
  text-decoration: none;
  color: var(--fg);
  border: 1px solid var(--border);
  background: transparent;
}

.tree__link:hover {
  background: var(--accent-wash);
  border-color: rgba(34, 197, 94, 0.35);
}