And just a slightly different point of view, to find the monkey:
This was really fun to do.
My first big discovery: there were hinges back in 1995.
Second discovery: actually, there wasn't much dark grey at all in 1995 (and although the rules allowed it, so I just didn't use it).
Third discovery: there were already jumpers. But of a type with a bottom stud holder. And so you couldn't make them jump a bit yourself already. I did use the new version, but with the old restrictions.
Anyway, I won't give any more tips, otherwise others won't have anything else to figure out.