style.css

* {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
  font-family: sans-serif
}

html,
body {
  height: 100%
}

body {
  padding: 16px 32px
}

body,
#container,
#upload-button {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center
}

h1 {
  text-align: center
}

#container {
  position: relative;
  width: 640px;
  height: 420px;
  max-width: 100%;
  max-height: 100%;
  border: 2px dashed #D1D5DB;
  border-radius: .75rem;
  overflow: hidden;
  margin-top: 1rem;
  background-size: 100% 100%;
  background-position: center;
  background-repeat: no-repeat
}

#mask-output {
  position: absolute;
  width: 100%;
  height: 100%;
  pointer-events: none
}

#upload-button {
  gap: .4rem;
  font-size: 18px;
  cursor: pointer
}

#upload {
  display: none
}

svg {
  pointer-events: none
}

#example {
  font-size: 14px;
  text-decoration: underline;
  cursor: pointer
}

#example:hover {
  color: #2563eb
}

canvas {
  position: absolute;
  width: 100%;
  height: 100%
}

#status {
  min-height: 16px;
  margin: 8px 0
}

input[type=range] {
  position: absolute;
  top: 10px;
  right: 10px;
  z-index: 1
}

#drop-zone {
  display: none;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  justify-content: center;
  align-items: center;
  font-size: 20px;
  background-color: rgba(0, 0, 0, 0.5);
  color: white;
}

#container.drag-over #drop-zone {
  display: flex;
}