Source code repo for the NL player contains, in a subfolder of "data", a copy of the NeoLemmix Introduction Pack.
Except that this copy is pretty corrupt. I suspect it was converted at an early point in new-formats development, in particular, a point at which there were attempts to trim empty space from terrain pieces, as well as merge duplicates that are just rotated / flipped / etc versions of each other. Because the eventual new-formats releases used untrimmed pieces (this idea was ditched because it was too buggy and, quite honestly, I was just too lazy to fix it), this version of NLI doesn't work on it.
Should either be removed, or replaced with a non-corrupt copy. I have absolutely no preference either way as to which approach is taken.
