code: function atkeyframes() {
      var pos = position();
      var m = match(/^@([-\w]+)?keyframes\s*/);
  
      if (!m) return;
      var vendor = m[1];
  
      // identifier
      var m = match(/^([-\w]+)\s*/);
      if (!m) return error("@keyframes missing name");
      var name = m[1];
  
      if (!open()) return error("@keyframes missing '{'");
  
      var frame;
      var frames = comments();
      while (frame = keyframe()) {
        frames.push(frame);
        frames = frames.concat(comments());
      }
  
      if (!close()) return error("@keyframes missing '}'");
  
      return pos({
        type: 'keyframes',
        name: name,
        vendor: vendor,
        keyframes: frames
      });
    }
docs: Parse keyframes.