body { background-color: #f8f9fa; }
.sidebar { min-height: 100vh; background-color: #343a40; color: white; }
.sidebar a { color: rgba(255,255,255,.75); text-decoration: none; padding: 10px 20px; display: block; }
.sidebar a:hover, .sidebar a.active { color: white; background-color: rgba(255,255,255,.1); }
.content { padding: 20px; }
.login-container { max-width: 400px; margin: 100px auto; padding: 20px; background: white; border-radius: 8px; shadow: 0 0 10px rgba(0,0,0,0.1); }
.hidden { display: none; }
.img-preview { max-width: 100px; max-height: 100px; margin-top: 10px; }