html, body{ margin: 0; user-select: none; overflow: hidden;}
.content {width: 108px; height: 108px; background-color: #fff; border-radius: 5px; }
.content>div{ display: flex; }
.content>div>div{ width: 12px; height: 12px; box-sizing: border-box; border-right: 1px solid #999; border-bottom: 1px solid #999; }
.content>div:first-child>div{ border-top: 1px solid #999; }
.content>div>div:first-child { border-left: 1px solid #999; }
.content>div:first-child>div:first-child { border-top-left-radius: 4px; }
.content>div:first-child>div:last-child { border-top-right-radius: 4px; }
.content>div:last-child>div:first-child { border-bottom-left-radius: 4px; }
.content>div:last-child>div:last-child { border-bottom-right-radius: 4px; }
.center { position: relative; }
.center>div{ position: absolute; top: -2px; left: -2px; width: 100%; height: 100%; border: 2px solid #fff; box-shadow: 0 0 1px #212121; }
