body {
    font-family: 'SF Pro Display', -apple-system, sans-serif;
    background-color: #f5f5f7;
    margin: 0;
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
}

header {
    text-align: center;
    margin-bottom: 30px;
}

h1 {
    font-size: 2.5em;
    color: #1d1d1f;
    font-weight: 600;
}

main {
    width: 100%;
    max-width: 400px;
}

label {
    display: block;
    margin: 15px 0 5px;
    font-size: 1.1em;
    color: #1d1d1f;
}

input[type="number"], select {
    width: 100%;
    padding: 12px;
    font-size: 1em;
    border: 1px solid #d2d2d7;
    border-radius: 8px;
    box-sizing: border-box;
}

input[type="checkbox"] {
    margin-right: 10px;
}

.fuel-options {
    margin: 10px 0;
}

.fuel-options label {
    display: inline-block;
    margin-right: 20px;
    font-size: 1em;
}

button, .button {
    display: block;
    width: 100%;
    padding: 15px;
    margin-top: 20px;
    background-color: #0071e3;
    color: white;
    border: none;
    border-radius: 10px;
    font-size: 1.2em;
    cursor: pointer;
    text-align: center;
    text-decoration: none;
}

button:hover, .button:hover {
    background-color: #005bb5;
}

#results p {
    font-size: 1.2em;
    margin: 10px 0;
    color: #1d1d1f;
}

@media (min-width: 768px) {
    main {
        max-width: 500px;
    }
    h1 {
        font-size: 3em;
    }
}