:root {
  --bg: #f8f9fc;
  --bg-card: #ffffff;
  --bg-input: #f1f3f8;
  --text: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --primary: #6366F1;
  --primary-light: rgba(99,102,241,0.08);
  --accent: #10b981;
  --border: #e2e8f0;
  --border-strong: #cbd5e1;
  --radius: 10px;
  --font: 'Inter',system-ui,sans-serif;
  --mono: 'JetBrains Mono',monospace;
  --transition: 0.2s ease;
  --shadow: 0 1px 3px rgba(0,0,0,0.06);
}

*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
body{font-family:var(--font);background:var(--bg);color:var(--text);min-height:100vh;overflow:hidden}

.header{display:flex;align-items:center;justify-content:space-between;padding:6px 16px;background:var(--bg-card);border-bottom:1px solid var(--border);height:42px;box-shadow:var(--shadow)}
.header-left,.header-right{display:flex;align-items:center;gap:8px}
.logo{font-size:1.1rem}
h1{font-size:0.92rem;font-weight:700;color:var(--primary)}

.btn{padding:5px 12px;border:1px solid var(--border);border-radius:8px;background:var(--bg-card);color:var(--text-secondary);font-family:var(--font);font-size:0.72rem;cursor:pointer;transition:all var(--transition)}
.btn:hover{border-color:var(--primary);color:var(--primary)}
.btn.primary{background:var(--primary);color:#fff;border-color:var(--primary);font-weight:600}
.btn.primary:hover{opacity:0.9}

.app-layout{display:flex;height:calc(100vh - 42px)}
.sidebar{width:300px;padding:10px;overflow-y:auto;border-right:1px solid var(--border);display:flex;flex-direction:column;gap:8px}
.preview-area{flex:1;display:flex;flex-direction:column;overflow:hidden}

.sec{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius);padding:10px;box-shadow:var(--shadow)}
.sec h3{font-size:0.68rem;font-weight:600;color:var(--text-muted);text-transform:uppercase;letter-spacing:.04em;margin-bottom:6px}

.form-group{margin-bottom:6px}
.form-group label{display:block;font-size:0.66rem;font-weight:500;color:var(--text-secondary);margin-bottom:2px}
.input{width:100%;padding:6px 8px;border:1px solid var(--border);border-radius:6px;background:var(--bg-input);color:var(--text);font-family:var(--font);font-size:0.78rem}
.input:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 2px var(--primary-light)}
.textarea{resize:vertical;font-family:var(--font)}

.style-grid{display:grid;grid-template-columns:1fr 1fr;gap:4px}
.style-btn{padding:6px;border:1px solid var(--border);border-radius:6px;background:var(--bg-card);color:var(--text-secondary);font-size:0.68rem;cursor:pointer;transition:.2s}
.style-btn:hover{border-color:var(--primary)}
.style-btn.active{border-color:var(--primary);color:var(--primary);background:var(--primary-light)}

.check-group{display:flex;flex-direction:column;gap:2px}
.check{font-size:0.72rem;color:var(--text-secondary);cursor:pointer;display:flex;align-items:center;gap:4px}
.check input{accent-color:var(--primary)}

/* Tabs */
.preview-tabs{display:flex;gap:0;border-bottom:1px solid var(--border);background:var(--bg-card)}
.tab{padding:8px 16px;border:none;background:transparent;color:var(--text-muted);font-family:var(--font);font-size:0.75rem;cursor:pointer;border-bottom:2px solid transparent;transition:.2s}
.tab.active{color:var(--primary);border-bottom-color:var(--primary)}

.preview-content{flex:1;overflow-y:auto;padding:20px 30px;background:var(--bg-card);font-size:0.85rem;line-height:1.7}
.preview-content h1{font-size:1.6rem;margin-bottom:8px;border-bottom:2px solid var(--border);padding-bottom:8px}
.preview-content h2{font-size:1.15rem;margin-top:20px;margin-bottom:8px;color:var(--text)}
.preview-content h3{font-size:0.95rem;margin-top:14px;margin-bottom:6px}
.preview-content p{margin-bottom:8px;color:var(--text-secondary)}
.preview-content code{background:var(--bg-input);padding:2px 5px;border-radius:4px;font-family:var(--mono);font-size:0.8rem}
.preview-content pre{background:#1e293b;color:#e2e8f0;padding:12px;border-radius:8px;overflow-x:auto;margin:8px 0;font-family:var(--mono);font-size:0.78rem}
.preview-content ul,.preview-content ol{margin:6px 0 6px 20px}
.preview-content li{margin-bottom:3px}
.preview-content img{max-height:22px;vertical-align:middle;margin-right:4px}
.preview-content a{color:var(--primary);text-decoration:none}
.preview-content blockquote{border-left:3px solid var(--primary);padding-left:12px;color:var(--text-muted);margin:8px 0}
.preview-content table{width:100%;border-collapse:collapse;margin:8px 0}
.preview-content th,.preview-content td{border:1px solid var(--border);padding:6px 10px;text-align:left;font-size:0.78rem}
.preview-content th{background:var(--bg-input)}

.raw-content{flex:1;resize:none;border:none;background:#1e293b;color:#e2e8f0;font-family:var(--mono);font-size:0.78rem;padding:16px;line-height:1.6}

@media(max-width:700px){
  .app-layout{flex-direction:column}
  .sidebar{width:100%;border-right:none;border-bottom:1px solid var(--border);max-height:45vh}
}