This guide really was a big help; not so much because i followed it , but moreso because it comes across as being written honestly and by someone who would have gone thru the struggles of tackling the great beast called perfect dark zero.
Personally I thought the game was(is) a masterpiece. I also think that many of the negative reviews were influenced by the toughness of the game and not because the game was actually bad.
When i first started to play this game i refused to start playing the campaign on agent or secret agent, opting instead for perfect agent cause i thought i was a pretty good gamer. Well i got my tail kicked in short order and had to go back to agent/secret agent to learn the levels properly (lol)
It's not strictly a linear game either......true you are moving from point A to point B but the ways to get there are multiple and A.I does tend to move around according to your actions