index.css

@-ms-viewport {
  width: device-width;
}

body {
  width: 100%;
  margin: 0;
  padding: 0;
  font-family: sans-serif;
}
header {
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  height: 250px;
  border-bottom: 1px solid rgba(0, 0, 0, 0.1);
}
header h1 {
  font-size: 36px;
  margin: 0;
}
header p {
  text-align: center;
  font-size: 18px;
}
main {
  position: relative;
  width: 100%;
  display: flex;
  margin: 50px 0;
  min-height: 62vmin;
  padding: 0;
  justify-content: center;
  align-items: center;
  overflow: hidden;
  font-family: sans-serif;
}
canvas {
  display: block;
  width: 62vmin;
  height: 62vmin;

  border: 1rem solid white;
  box-shadow: 0 0 1rem 0 rgba(0, 0, 0, 0.1);
}
overlay- {
  position: absolute;
  display: flex;
  align-items: center;
  min-height: 62vmin;
  top: 16px;
  left: 0;
  width: 100%;
  pointer-events: none;
}
overlay- img {
  display: block;
  width: 62vmin;
  height: 62vmin;
  margin-left: calc(50% - 31vmin);
  pointer-events: none;
  background: #f2f2f2;
  flex: none;
}
overlay- img.active {
  background: transparent;
}
overlay- img:not(.active) {
  transform: scale(0.618);
}

button {
  border: 0;
  padding: 1rem 2rem;
  background: #eee;
  font-size: 22px;
  font-weight: bold;
  outline: none;
  color: #999;
  margin: 30px 0 30px 0;
}

button:hover {
  color: #666;
}

controls- {
  text-align: center;
  bottom: 0;
  left: 0;
  padding: 50px 0px;
  width: 100%;
}

.upload {
  position: relative;
  text-align: center;
  margin: 50px 0 0 0;
  z-index: 10;
}

.upload-area {
  z-index: 999;
  padding: 30px 20px;
  width: 60%;
  margin: 0 auto;
  border: 1px dashed rgb(202, 202, 202);
  border-width: 5px;
  border-spacing: 10px;
  font-size: 20px;
  color: rgb(54, 54, 54);
}

#file-upload {
  display: block;
  z-index: 1000 !important;
  font-size: 24px;
  width: 100%;
  position: relative;
}

.download {
  color: #1793b3;
  border: 1px solid #1793b3;
  background-color: #fff;
  border-radius: 50px;
  display: block;
  margin: 30px auto;
}

.download:hover {
  color: white;
  background-color: #1793b3;
}

@media screen and (max-width: 768px) {
  .upload-area {
    width: calc(90% - 40px);
  }
}