*,body{
  margin:0;
  padding:0;
  border-box:box-sizing;
}

body{
  width:100vw;
  height:100vh;
}
.rect{
    position: relative;
    width:100%;
    height: 100%;
    overflow:hidden;
    background: radial-gradient(circle, #56b0fac7 , #0064fb)    ;
}

.ball{
    position: absolute;
    width:50px;
    height: 50px;
    line-height: 50px;
    text-align: center;
    color:wheat;
    border-radius: 50%;
    background-color:red;
    left:20px;
}