.dia-source img {
  width: 100px;
  margin: 5px;
  cursor: grab;
}

.dia-canvas {
  border: 2px dashed #aaa;
  min-height: 300px;
  position: relative;
  margin-top: 20px;
}

.dia-canvas img {
  position: absolute;
  width: 100px;
}