OMFG I just lost another couple of hours because I went in an area where the I couldn't go back the way I came (could only go forward but I was getting my ass kicked). I had an older save to go back to this time but I'm still pissed.
Had to look up a faq to find the holy grail, I would have NEVER found the secret passage otherwise. Is the whole game filled with hidden, mandatory-to-progress, shit like this ?
Well the Holy Grail was one of the most bullshit puzzles IMO, largely because it comes so early in the game before you realize just how devious this game is. But yeah, there will be more "and how was I supposed to know that?
" moments, and if you finish the rest of the game without a walkthrough, then you are more hardcore than I.
Once you have the holy grail, the scanner, and the tablet reading software, though, it should no longer be possible to get stuck, because you always have the option of warping back to the surface.