<div class="block b1">
<div class="arc arc1"></div>
</div>

html {
  margin-top: 0px !important;
}

body{
padding:0px;
margin:0px;
background-color: #333;
}

.block{
background-color: white;
}

.b1{
width: 90%;
height:90vh;
  display:flex;
  align-items: center;
  justify-content: center;
}
.arc1{
width:100%;
max-width: 200px;
height:200px;
background-color: #000;
background-color: #000;
display: flex;
flex-basis: 200px;
}