:root {
    --main-color: #2c3e50;
    --hover-color: #34495e;
}
body {
    background-color: #f8f9fa;
    min-height: 100vh;
}
.container {
    max-width: 1000px;
    margin: 50px auto;
    padding: 30px;
    background: white;
    border-radius: 15px;
    box-shadow: 0 0 15px rgba(0,0,0,0.1);
}
#drop-zone {
    border: 3px dashed var(--main-color);
    padding: 40px 20px;
    text-align: center;
    margin: 25px 0;
    transition: 0.3s;
    cursor: pointer;
    background: #f8f9fa;
}
#drop-zone:hover {
    background: #e9ecef;
    border-color: var(--hover-color);
}
.alert {
    margin-top: 20px;
    padding: 15px;
    border-radius: 8px;
}