<div class="tomoe"></div>

.tomoe{
width:100px;
height:100px;
border-radius:50%;/*角を丸めて円に*/
margin:0 auto;/*中央寄せ*/
background-image:
linear-gradient(-40deg,#000 36.3px,transparent 0),
linear-gradient(-65deg,#000 35.3px,transparent 0),
linear-gradient(-55deg,#000 40.5px,transparent 0),
radial-gradient(#000 24px,transparent 0),
radial-gradient(#000 24px,transparent 0),
radial-gradient(#fff 37px,transparent 0),
linear-gradient(90deg,#000 50%,transparent 0),
radial-gradient(#fff 37px,#000 0);
border:solid 0px #000;
background-position:0px -10px,0px 0px,0px 0px,0px -26px,0px 26px,0 13px,0px 0px,0px -13px;
}

<center><a href="" class="tomoeA">リンク文字</a></center>

.tomoeA{
display:inline-block;/*a要素に幅や高さを指定する為に必要*/
width:100px;
height:100px;
border-radius:50%;/*角を丸めて円に*/
color:#c00;/*リンク文字の色(赤)*/
text-shadow:/*リンク文字の2方向に白い影*/
1px 1px 0px #fff,/*右下*/
-1px -1px 0px #fff;/*左上*/
font-weight:bold;/*リンク文字を太字に*/
text-decoration:none;/*リンク文字の下線を消す*/
line-height:100px;/*リンク文字を中央に(縦方向)*/
text-align:center;/*リンク文字を中央に(横方向)*/
background-image:
linear-gradient(-40deg,#000 36.3px,transparent 0),
linear-gradient(-65deg,#000 35.3px,transparent 0),
linear-gradient(-55deg,#000 40.5px,transparent 0),
radial-gradient(#000 24px,transparent 0),
radial-gradient(#000 24px,transparent 0),
radial-gradient(#fff 37px,transparent 0),
linear-gradient(90deg,#000 50%,transparent 0),
radial-gradient(#fff 37px,#000 0);
border:solid 0px #000;
background-position:0px -10px,0px 0px,0px 0px,0px -26px,0px 26px,0 13px,0px 0px,0px -13px;
}