style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.main {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 90%; 
    max-width: 800px; 
}

.canvas {
    border: 2px solid black;
    width: 100%; 
    height: auto; 
}

.top,
.bottom {
    display: flex;
    flex-direction: column; 
    align-items: center;
    margin: 20px 0;
}

.block,
input,
select,
button {
    width: 100%; 
    max-width: 300px; 
}

.top > .block {
    margin: 10px 0;
}

.bottom > button {
    margin: 10px 0;
}

.block > p {
    margin: 10px auto;
    width: auto; 
}


@media (min-width: 600px) {
    .top,
    .bottom {
        flex-direction: row; 
        justify-content: space-between; 
    }

    .block,
    input,
    select,
    button {
        width: 45%; 
    }
}