:root { --bg: #fafafa; --fg: #1a1a1a; --accent: #4f46e5; --muted: #6b7280; --border: #e5e7eb; }
* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Inter, sans-serif;
       background: var(--bg); color: var(--fg); line-height: 1.6; }
nav { display: flex; justify-content: space-between; align-items: center;
      max-width: 1100px; margin: 0 auto; padding: 20px; }
nav .logo { font-weight: 700; font-size: 1.3em; color: var(--accent); text-decoration: none; }
nav .links a { color: var(--muted); text-decoration: none; margin-left: 24px;
               font-size: 0.95em; transition: color 0.2s; }
nav .links a:hover { color: var(--fg); }
.hero { max-width: 1100px; margin: 80px auto 60px; padding: 0 20px; text-align: center; }
.hero h1 { font-size: 2.8em; font-weight: 800; letter-spacing: -0.03em; margin-bottom: 16px; }
.hero p { font-size: 1.2em; color: var(--muted); max-width: 560px; margin: 0 auto 32px; }
.hero .btn { display: inline-block; background: var(--accent); color: #fff;
             padding: 14px 32px; border-radius: 8px; text-decoration: none;
             font-weight: 600; transition: opacity 0.2s; }
.hero .btn:hover { opacity: 0.9; }
.features { max-width: 1100px; margin: 0 auto 80px; padding: 0 20px;
            display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 32px; }
.feature { background: #fff; border: 1px solid var(--border); border-radius: 12px; padding: 32px; }
.feature h3 { margin-bottom: 8px; font-size: 1.1em; }
.feature p { color: var(--muted); font-size: 0.95em; }
.stats { background: #fff; border-top: 1px solid var(--border);
         border-bottom: 1px solid var(--border); padding: 48px 20px; text-align: center; }
.stats .grid { max-width: 800px; margin: 0 auto;
               display: grid; grid-template-columns: repeat(3, 1fr); gap: 32px; }
.stats .num { font-size: 2em; font-weight: 700; color: var(--accent); }
.stats .label { color: var(--muted); font-size: 0.9em; }
footer { max-width: 1100px; margin: 0 auto; padding: 40px 20px;
         display: flex; justify-content: space-between; color: var(--muted); font-size: 0.85em; }
footer a { color: var(--muted); text-decoration: none; }
.content { max-width: 680px; margin: 40px auto; padding: 0 20px; }
.content h1 { font-size: 2em; margin-bottom: 24px; }
.content h2 { font-size: 1.3em; margin: 32px 0 12px; }
.content p { margin-bottom: 16px; color: #374151; }
.content a { color: var(--accent); }
.app { display: flex; height: 100vh; }
.sidebar { width: 280px; background: #fff; border-right: 1px solid var(--border);
           padding: 20px; overflow-y: auto; }
.sidebar h2 { font-size: 1.1em; margin-bottom: 16px; color: var(--accent); }
.sidebar .note-item { padding: 10px 12px; border-radius: 6px; cursor: pointer;
                      margin-bottom: 4px; transition: background 0.15s; }
.sidebar .note-item:hover { background: #f3f4f6; }
.sidebar .note-item.active { background: #eef2ff; border-left: 3px solid var(--accent); }
.sidebar .note-item .title { font-weight: 600; font-size: 0.9em; }
.sidebar .note-item .date { font-size: 0.75em; color: var(--muted); }
.editor { flex: 1; display: flex; flex-direction: column; }
.editor .toolbar { padding: 12px 20px; border-bottom: 1px solid var(--border);
                  display: flex; gap: 8px; }
.editor .toolbar button { background: none; border: 1px solid var(--border);
                          padding: 6px 12px; border-radius: 4px; cursor: pointer;
                          font-size: 0.85em; color: var(--muted); }
.editor textarea { flex: 1; padding: 24px; border: none; resize: none;
                  font-family: 'SF Mono', 'Fira Code', monospace; font-size: 0.95em;
                  line-height: 1.7; outline: none; background: #fff; }
.status { padding: 8px 20px; border-top: 1px solid var(--border);
          font-size: 0.75em; color: var(--muted); display: flex; justify-content: space-between; }
@media (max-width: 600px) {
    .hero h1 { font-size: 1.8em; }
    .stats .grid { grid-template-columns: 1fr; }
    footer { flex-direction: column; gap: 12px; }
}