Exactly my situation as well - totally get the logic of what to do in the next room, just can't find a way to get two cats at the top, then one rock, then another cat at the bottom. That's the problem.
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...