body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: #f3f4f6;
    color: #1f2937;
    margin: 0;
    padding: 20px;
}
header {
    text-align: center;
    background: #1e3a8a;
    color: white;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 20px;
}
main {
    max-width: 800px;
    margin: 0 auto;
}
section {
    background: white;
    padding: 20px;
    border-radius: 8px;
    margin-bottom: 20px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
input[type="text"], input[type="password"] {
    width: 80%;
    padding: 10px;
    border: 1px solid #d1d5db;
    border-radius: 4px;
}
button {
    background: #1e3a8a;
    color: white;
    border: none;
    padding: 10px 15px;
    border-radius: 4px;
    cursor: pointer;
}
button:hover { background: #1e40af; }
.drop-zone {
    border: 2px dashed #1e3a8a;
    padding: 30px;
    text-align: center;
    background: #eff6ff;
    cursor: pointer;
    border-radius: 6px;
}
.chat-box {
    height: 300px;
    overflow-y: auto;
    border: 1px solid #e5e7eb;
    padding: 10px;
    background: #fafafa;
    border-radius: 4px;
    margin-bottom: 10px;
}
.message { margin-bottom: 10px; padding: 8px; border-radius: 4px; }
.user-msg { background: #e0f2fe; text-align: right; }
.ai-msg { background: #f3f4f6; text-align: left; }