.diagram:before { left: calc( (450px - 100px) / 2 ) } /*sticky tape*/
table.form {
  margin-bottom: 0;
  width: calc(100% - 450px - 1px - 1px - 1em);
}

@media only screen and (max-width: 600px) { /*ruler breakpoint*/
  table.form { width: inherit }
}