@-moz-document regexp("(\d{0,15})") {
  a {
    color: red;
  }
}
.custom-property {
  --this: () => {
    basically anything until final semi-colon;
    even other stuff; // i\'m serious;
  };
  --that: () => {
    basically anything until final semi-colon;
    even other stuff; // i\'m serious;
  };
  --custom-color: #ff3333 #ff3333;
  custom-color: #ff3333 #ff3333;
}
.var {
  --fortran: read (*, *, iostat=1) radius, height;
}
@-moz-whatever (foo: "(" bam ")") {
  bar: foo;
}
#selector,
.bar,
foo[attr="blah"] {
  bar: value;
}
@media (min-width: 640px) {
  .holy-crap {
    this: works;
  }
}
.test-rule-comment {
  --value: a /* { ; } */;
  --comment-within: ( /* okay?; comment; */ );
}