html, body {
  margin: 0;
  padding: 0;
  height: 100vh;
  width: 100vw;
  overflow: hidden;
}

.viewport {
  position: relative;
  width: 100%;
  height: 100%;
  background: #111;
  color: white;
  font-family: sans-serif;
  overflow: hidden;
}

/* Generic overlay base */
.overlay {
  position: absolute;
  padding: 0.5em 1em;
  background: rgba(0, 0, 0, 0.6);
  border-radius: 0.5em;
  user-select: none;
  cursor: pointer;
}

/* Corners */
.top-left {
  top: 1em; left: 1em;
}
.top-right {
  top: 1em; right: 1em;
}
.bottom-left {
  bottom: 1em; left: 1em;
}
.bottom-right {
  bottom: 1em; right: 1em;
}

/* Edges */
.top-center {
  top: 1em; left: 50%; transform: translateX(-50%);
}
.bottom-center {
  bottom: 1em; left: 50%; transform: translateX(-50%);
}
.left-center {
  left: 1em; top: 50%; transform: translateY(-50%);
}
.right-center {
  right: 1em; top: 50%; transform: translateY(-50%);
}

/* Center */
.center {
  top: 50%; left: 50%; transform: translate(-50%, -50%);
}