.sonic-gas-wrap {
  text-align: center;
  margin-top: 10px;
}

/* GAS CONTAINER */
.sonic-gas-box {
  position: relative;
  width: 260px;
  height: 180px;
  margin: 0 auto;
  background: #cfcfcf;
  border: 2px solid #666;
  overflow: hidden;
}

/* PARTICLES */
.sonic-particle {
  position: absolute;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #9a9a9a;
  box-shadow: inset -1px -1px 2px rgba(0,0,0,0.3);
}

/* PRESSURE WAVE */
.sonic-wave {
  position: absolute;
  top: 0;
  left: -40px;
  width: 40px;
  height: 100%;
  background: rgba(30, 64, 175, 0.15);
  animation: waveMove 2.2s linear infinite;
}

/* WAVE ANIMATION */
@keyframes waveMove {
  from { left: -40px; }
  to   { left: 260px; }
}

/* CAPTION */
.sonic-caption {
  margin-top: 6px;
  font-size: 12px;
  color: #333;
}