What do you mean? It's a 55mb download.

If it doesn't run, it's probably due to missing libraries. This can be fixed easily if I know what’s wrong. If you run puzzle1.sh in the game's directory from a terminal it should show the missing library. If you need detailed steps i can provide them.

You're missing the point... the game fails to download, there are no files.

That's odd... I have the depot visible as 55mb in Steamworks and have it downloaded myself (I run Ubuntu 16.xx at home) and everything appears to work fine. I've just verified files of my download and that confirms this works for me.

What are your machine/OS specs?

i5 + GTX1050Ti + 8Gb RAM + SSD + Ubuntu 17.04(64)

On the download page it said 0 bytes / 0 bytes

I've adjusted the depot settings as I think the 64-bit only settings might have been confusing Steam (it's not really clear). Has this helped? Reinstalling it should show if this was the issue.

Nope :(

I uninstall then install.. I immediately get the popup steam notification that Puzzle One has finished downloading, but on the download screen it says 0 bytes / 0 bytes and when I try to play the game it says "An error occurred while updating Puzzle One (missing executable)" and the Puzzle One directory under steam is empty.

Figured it out. The release package was missing the Linux depot. If you're unfamiliar with Steamworks, this setting is buried in a really obscure place. Hope this fixes it.

Success! Thanks!