body{margin:0;font-family:Arial,sans-serif;background:#f4f6fb}
.sidebar{position:fixed;left:0;top:0;bottom:0;width:240px;background:#fff;padding:20px}
.sidebar a{display:block;margin:10px 0}
.content{margin-left:260px;padding:20px}
.card{background:#fff;padding:16px;border-radius:16px;margin-bottom:12px}
.view{display:none}.active{display:block}
.dark{background:#111827;color:#fff}
.dark .card,.dark .sidebar{background:#1f2937;color:#fff}
@media(max-width:900px){.sidebar{position:static;width:auto}.content{margin-left:0}}