<button class="exitnew" type="button" aria-label="Close"><b></b></button>

<button class="exitnew" type="button" aria-label="Close"><b></b></button>

<button class="exitnew" type="button" aria-label="Close"><b></b></button>

<button class="exitnew exit2" type="button" aria-label="Close"></button>
html,
body {
  padding: 0;
  margin: 0;
}
body {
  background: url(https://picsum.photos/id/1015/1500/1500) no-repeat;
  background-attachment: fixed;
  background-size: cover;
}
.exitnew {
  -webkit-appearance: none;
  appearance: none;
  position: relative;
  box-sizing: border-box;
  margin: auto;
  padding: 0;
  width: 48px;
  height: 48px;
  cursor: pointer;
  background: blue;
  border: none;
  border-radius: 50%;
  clip-path: circle(50%);
  transition: all 1s ease;
  overflow: hidden;
}
.exitnew:before,
.exitnew:after {
  content: "";
  position: absolute;
  height: 5px;
  top: 22px;
  left: -1px;
  right: -1px;
  background: red;
  transform: rotate(45deg);
  transition: all 1s ease;
  z-index: 1;
}
.exitnew:after {
  transform: rotate(-45deg);
}
.exitnew:hover {
  background: transparent;
}
.exitnew:hover:before,
.exitnew:hover:after {
  background: green;
}
.exitnew b {
  box-sizing: border-box;
  position: absolute;
  z-index: 2;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  border: 5px solid red;
  border-radius: 50%;
}

/*  additional hanges for  4th example without b element */
.exit2 {
  border: 5px solid red;
}

.exit2:before,
.exit2:after {
  top: 17px;
}
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