style.css

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

body {
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
}
#canvas {
    max-width: 60vw;
    max-height: 100vh;
}
@media only screen and (max-width: 640px) {
    #canvas {
        justify-items: center;
        margin-left: auto;
        margin-right: auto;
        max-width: 100vw;
        max-height: 60vh;
    }
}
.panel {
    padding-left: 1.5rem;
    padding-right: 1.5rem;
    padding-top: 1.5rem;
}
input[type="file"] {
    position: absolute;
    z-index: -1;
    top: 10px;
    left: 14px;
    font-size: 17px;
    color: #b8b8b8;
  }
.button-wrap {
    position: relative;
}
.button {
    display: inline-block;
    padding: 12px 18px;
    cursor: pointer;
    border-radius: 5px;
    background-color: red;
    font-size: 16px;
    font-weight: bold;
    color: #fff;
}
.range {
    width: 20rem;
}
.setting {
    display: flex;
    flex-direction: column;
}
.setting div label{
    display: block;
}
button {
    border: none;
}
.button#reset, .button#download {
    flex: none;
    width: fit-content;
    padding-top: 0.3rem;
    padding-bottom: 0.3rem;
    margin-top: 0.3rem;
    margin-right: 0.3rem;
}
.button#reset {
    background-color: rgb(85, 83, 83);
}
.button#download {
    display: none;
}