Nice, but why "invisible sky"? I didn't get it. Are you saying the sky was gray and boring? Or did you mean the wind? Thanks!
Yes, the sky was hiding behind a thick gray envelop; stormy weather .. and I thought that the word invisible gives the "scary" sensation to the haiku :) Would you prefer:A gray sky;The lonely swingGoes back and forth
If you want scary, what about this:Menacing skies:The empty swingGoes back and forth"Empty" looks more sinister than "lonely" which is more "romantic."Skies in plural more interesting than sky, and also more frighteningColon better than semi-colon as it says "look!" and is not merely a pause.
WOW!!! Impressive explanation!! I take it :) Thank you!So, before modification:An invisible sky;The empty swingGoes back and forthAfter modification:Menacing skies:The empty swingGoes back and forth