Hi Scott, thanks for trying it out and for the feedback. :)
> Shadow - it desperately needs some kind of shadow, a body shaped one would be great but even just a blob would make a massive difference to making you feel that you're actually there.
There is a subtle blob shadow below the player, but maybe it's so faint that it's not very noticeable. A more realistic shadow is hard when I don't know where the player's body is exactly.
> Sound - this is the area that needs the most improvement imo. Heavy sounds of sliding blocks, sounds in your ears to put you off, the sound of wind, step sounds when you get onto the blocks etc.
Sounds needs a lot of improvement, agreed. That said, there are sounds of sliding blocks already. Did you hear sound at all, because if not, it might be an sound output problem perhaps?
I'm noting down your ideas for variation - some of them match some things I was already wanting to do. :)