body {
  margin: 0;
  width: 100%;
  box-sizing: border-box;
}
img {
  width: 100%;
  max-height: 30vh;
  object-fit: contain;
}
canvas {
  width: 100%;
  border: solid 0.1rem #333;
  box-sizing: border-box;
}

label {
  display: inline-block;
  min-width: 4em;
  text-align: right;
}
input[type='text'] {
  width: 5em;
}
button[id^='inc_'],
button[id^='dec_'],
input[type='checkbox'] {
  width: 10mm;
  height: 10mm;
  vertical-align: middle;
}

#content {
  margin: auto;
  max-width: 60rem;
  padding: 1rem;
}

.hidden {
  display: none;
}
.invalid {
  background-color: #faa;
}