body {
        background: linear-gradient(135deg, #4a90e2, #50a0f0);
        min-height: 100vh;
        display: flex;
        align-items: center;
        justify-content: center;
        font-family: 'Segoe UI', sans-serif;
    }
    .card {
        border-radius: 20px;
        box-shadow: 0 15px 40px rgba(0,0,0,0.2);
        padding: 35px;
        background: #fff;
        width: 100%;
        max-width: 520px;
        transition: transform 0.3s, box-shadow 0.3s;
    }
    .card:hover { 
        transform: translateY(-5px); 
        box-shadow: 0 20px 50px rgba(0,0,0,0.25);
    }
    h3 {
        text-align: center;
        margin-bottom: 30px;
        color: #333;
        font-weight: 600;
    }
    .form-control {
        border: 2px solid #4a90e2;
        border-radius: 8px;
        transition: all 0.3s;
    }
    .form-control:focus {
        border-color: #007bff;
        box-shadow: 0 0 10px rgba(0,123,255,0.5);
    }
    #codigo-container {
        display: none;
        transition: all 0.3s;
    }
    #msg {
        margin-top: 15px;
        font-weight: 500;
        min-height: 25px;
    }
    .btn-primary {
        background: #4a90e2;
        border: none;
        font-weight: 600;
        transition: background 0.3s, transform 0.2s;
    }
    .btn-primary:hover {
        background: #007bff;
        transform: translateY(-2px);
    }