*{
  margin: 0;
  padding: 0;
}
header{

    background: #a6b4c5;

}
.container{

  background: #fff;
}



li{
  
  background-color: bisque;
  position: relative;
  padding: 5px;
}

.select{
  position: absolute;
}

li::before{

  content:'';

}

li:has(.select:checked) .task-text {
  text-decoration: line-through;
  opacity: 0.6;
}