Edit in JSFiddle

<div class="box">Блок</div>

body {
  color: #fff;
  font: 600 14px/24px "Open Sans", "HelveticaNeue-Light", "Helvetica Neue Light", "Helvetica Neue", Helvetica, Arial, "Lucida Grande", Sans-Serif;
}
.box {
  background: #2db34a;
  border-radius: 6px;
  cursor: pointer;
  height: 95px;
  line-height: 95px;
  text-align: center;
  transition-property: background, border-radius;
  transition-duration: .2s, 1s;
  transition-timing-function: linear;
  width: 95px;
}
.box:hover {
  background: #ff7b29;
  border-radius: 50%;
}