Things rapidly get larger then smaller, back and forth. For me, my vision would also sometimes do this thing where I'd have both eyes open, but it would look like I was winking one, then the other, back and forth really fast.

I also liked how even a little dxm would enhance weed like crazy.

It got to where I couldn't keep any liquid dxm down at all and I hated polystirex so robitussin in the blue bottle was the only thing that worked for me. Eventually I got tired of swallowing entire bottles of big, dry pills so I retired from it permanently.