Hm. I've tried for a long time now. My assumption was for a period that there needs to be a dead cat in the field right below the rock that I will push with an alive cat as well as the two alive cats above the rock, but I can't get it to work. Could you please give some hints as to where the dead cat(s) need to be to be able to exit 9,12 with two cats above the rock and one beneath? I assume I need four cats (entering 9,12 with three cats) to make it all work, or do I just need three?
I got it! Dead cats are the key, specifically, (rot13) Trg n cnve bs pngf gb qvr ba gur pbairlbe whfg orsber nabgure fyvqrf bagb gur synt. Gura gur yvir png pna jnyx qbja nf gur qrnq pngf zbir gbjneqf gur synt. Jura gur svefg uvgf gur synt, zbir vg qbja naq lbh'yy unir gur beqre jr arrq.
Now I can go play all of DROD again...