I described extensively what I call "the shadow line artifact" in the VFAQ.
Direct URL:
http://iki.fi/warp/povVFAQ/TheShadowLineArtifact/
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
