body {
  font-family: sans-serif;
  margin: 0;
  padding: 20px;
  background-image: url("../img/pngtree-concrete-wall-texture-image_738498.jpg");
  height: 100vh;
  background-position: center;
}
#form {
  margin: 0;
  position: absolute;
  top: 50%;
  left: 50%;
  -ms-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}
#wall {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-start;
  align-items: flex-start;
  min-height: 50vh;
  height: 100%;
  overflow: hidden;
}
.message {
  margin: 10px;
  padding: 20px;
  border: none;
  text-align: center;
  /*width: 300px;*/
  transform: rotate(calc(var(--angle) * 360deg));
  position: absolute;
  left: calc(max(5vw, min(95vw, var(--random-left) * 100vw)));
  top: calc(max(5vh, min(90vh, var(--random-top) * 100vh)));

  transition: transform 0.5s ease;
  opacity: 0;
}
.message.visible {
  opacity: 1;
}