.wrapper {
    display: flex;
    justify-content: center;
    align-items: center;
}
.slider {
    max-width: 100%;
    margin: 50px auto;
}
.image-box img {
    max-width: 100%;
    height: auto;
    border: 5px solid purple;
    border-radius: 10px;
}
.btn {
    border: none;
    outline: none;
    background: #888;
    padding: 10px 20px;
    font-size: 16px;
    color: #ddd;
    cursor: pointer;
    margin: 10px auto;
}
.btn:hover {
    background: #111;
}
@media (min-width: 768px) {
    .slider {
        width: 400px;
    }

    .btn {
        font-size: 20px;
    }
}