.particles {
  background: #ddd;
  background-size: 100px 50px;
  height: 600px;
  margin: 10px auto;
  position: relative;
  width: 600px; }

.particle {
  background: url(../res/seahorse.svg) no-repeat center center;
  background-size: 20px 20px;
  border-color: salmon;
  border-style: dashed;
  border-radius: 50px;
  border-width: 1px;
  height: 100px;
  position: absolute;
  width: 100px; }

.highlight {
  animation: pulse 0.5s 1;
  border-radius: 15px;
  position: absolute; }

@keyframes pulse {
  from {
    border: 4px solid lightgreen;
    height: 30px;
    margin: -15px 0 0 -15px;
    width: 30px; }
  to {
    height: 0px;
    margin: 0;
    width: 0px; } }
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0; }

body {
  font-family: sans-serif; }