body {
    background: linear-gradient(135deg, #0f0f0f, #2c2c2c);
    color: #fff;
    margin: 0;
}

.card {
    width: 100%;
    max-width: 350px;
    background: #1f1f1f;
    border-radius: 15px;
    color: white;
    border: 1px solid rgba(255,255,255,0.1);
    box-shadow: 4px 2px 10px #aaa;
}

#fuelInput {
    background: #2b2b2b;
    border: 1px solid #444;
    color: white;
}

#fuelInput::placeholder {
    color: #aaa;
}

.btn-danger {
    transition: 0.3s;
}

.btn-danger:hover {
    background: #ff4d4d;
    transform: scale(1.02);
}

#message {
    min-height: 20px;
}