:root {
  --bg: #0b0d10;
  --surface: #111318;
  --surface-2: #1a1d24;
  --surface-3: #21262e;
  --text: #c9d0dc;
  --heading: #e8eef5;
  --accent: #6aa8ff;
  --accent-2: #4e9a06;
  --accent-3: #ff9f43;
  --border: #272b35;
  --code-bg: #0d0f13;
  --term-bg: #050608;
  --why-bg: rgba(106, 168, 255, 0.08);
  --warn-bg: rgba(255, 159, 67, 0.1);
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; background: var(--bg); color: var(--text); font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; }

#app { display: flex; height: 100vh; overflow: hidden; }

#sidebar {
  width: 320px;
  background: var(--surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  padding: 1rem;
  overflow-y: auto;
}

#sidebar h1 { font-size: 1.25rem; color: var(--heading); margin: 0 0 0.5rem; }
#progress { font-size: 0.8rem; color: var(--accent); margin-bottom: 0.8rem; }

#search {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.5rem;
  border-radius: 4px;
  margin-bottom: 0.8rem;
  width: 100%;
}

#search:focus { outline: none; border-color: var(--accent); }

#nav .group { margin-bottom: 1rem; }
#nav .group-title {
  text-transform: uppercase;
  font-size: 0.7rem;
  letter-spacing: 0.05em;
  color: #8a93a5;
  margin: 0.5rem 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
}
#nav .group-title:hover { color: var(--accent); }
#nav .group-title .toggle { font-size: 0.65rem; }
#nav .group.collapsed .items { display: none; }

#nav a {
  display: block;
  padding: 0.4rem 0.6rem;
  border-radius: 4px;
  color: var(--text);
  text-decoration: none;
  font-size: 0.85rem;
  cursor: pointer;
}
#nav a:hover { background: var(--surface-2); }
#nav a.active { background: var(--accent); color: #000; font-weight: 600; }
#nav a .done { color: var(--accent-2); margin-left: 0.25rem; }
#nav a.active .done { color: #000; }

#main { flex: 1; display: flex; flex-direction: column; overflow: hidden; }

#content {
  flex: 1;
  overflow-y: auto;
  padding: 2rem;
  max-width: 1000px;
}

#content h2 { color: var(--heading); margin-top: 0; }
#content h3 { color: var(--heading); margin-top: 1.5rem; }
#content h4 { color: var(--heading); margin-top: 1.2rem; font-size: 1rem; }
#content p { line-height: 1.7; }
#content pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1rem;
  overflow-x: auto;
}
#content code { font-family: 'Fira Code', 'SF Mono', monospace; font-size: 0.9rem; }
#content pre code { background: none; padding: 0; }
#content ul, #content ol { padding-left: 1.5rem; line-height: 1.7; }
#content blockquote { border-left: 3px solid var(--accent); margin-left: 0; padding-left: 1rem; color: #9ca5b5; }
#content .warn {
  background: var(--warn-bg);
  border: 1px solid var(--accent-3);
  border-radius: 6px;
  padding: 0.8rem 1rem;
  margin: 1rem 0;
}

.why-box {
  background: var(--why-bg);
  border: 1px solid var(--accent);
  border-radius: 8px;
  padding: 1rem 1.2rem;
  margin: 1.5rem 0;
}
.why-box h3 {
  margin-top: 0.5rem;
  color: var(--accent);
  font-size: 1rem;
}
.why-box .challenge {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.8rem 1rem;
  font-family: 'Fira Code', 'SF Mono', monospace;
  color: var(--heading);
}

.try-it {
  background: var(--accent);
  color: #000;
  border: none;
  padding: 0.4rem 0.8rem;
  border-radius: 4px;
  font-weight: 600;
  cursor: pointer;
  margin: 0.5rem 0.3rem 0.5rem 0;
}
.try-it:hover { background: #4e9aff; }

.progressive { border: 1px solid var(--border); border-radius: 6px; overflow: hidden; margin: 1rem 0; }
.progressive .p-title {
  background: var(--surface-2);
  padding: 0.6rem 1rem;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-weight: 600;
}
.progressive .p-body { padding: 1rem; display: none; }
.progressive.open .p-body { display: block; }
.progressive .p-title .p-toggle { color: var(--accent); }

#lab-panel {
  height: 360px;
  min-height: 220px;
  border-top: 1px solid var(--border);
  background: var(--term-bg);
  display: flex;
  flex-direction: column;
}

#lab-header {
  padding: 0.5rem 1rem;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 0.85rem;
  flex-wrap: wrap;
}

#lab-header span:first-child { font-weight: 600; color: var(--heading); }
#lab-status { margin-left: auto; font-size: 0.75rem; text-transform: uppercase; color: #8a93a5; }
#lab-status.ready { color: var(--accent-2); }
#lab-status.busy { color: var(--accent); }
#lab-status.error { color: #ff6b6b; }

#reset-lab, #record-lab {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.3rem 0.8rem;
  border-radius: 4px;
  cursor: pointer;
}
#reset-lab:hover, #record-lab:hover { background: var(--border); }

#lab-env-select {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
}

#terminal { flex: 1; padding: 0.5rem; }

.xterm { padding: 0.5rem; }
.xterm-viewport { background: var(--term-bg) !important; }

#search-results {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 4px;
  max-height: 200px;
  overflow-y: auto;
  margin-bottom: 0.8rem;
  display: none;
}
#search-results a {
  display: block;
  padding: 0.4rem 0.6rem;
  color: var(--text);
  text-decoration: none;
  font-size: 0.85rem;
}
#search-results a:hover { background: var(--surface-3); }
#search-results .empty { padding: 0.5rem; color: #8a93a5; font-size: 0.8rem; }