Placeholder selectors

Starts with a % and it’s not included in the
CSS output.
It can still be extended!

%toolbelt {
  box-sizing: border-box;
  border-top: 1px rgba(#000, .12) solid;
  padding: 16px 0;
  width: 100%;

  &:hover { border: 2px rgba(#000, .5) solid; }
}

.action-buttons {
  @extend %toolbelt;
  color: #4285f4;
}

.reset-buttons {
  @extend %toolbelt;
  color: #cddc39;
}

.reset-buttons, .action-buttons {
  box-sizing: border-box;
  border-top: 1px rgba(0, 0, 0, 0.12) solid;
  padding: 16px 0;
  width: 100%;
}
.reset-buttons:hover, .action-buttons:hover {
  border: 2px rgba(0, 0, 0, 0.5) solid;
}

.action-buttons {
  color: #4285f4;
}

.reset-buttons {
  color: #cddc39;
}