Posted on 24 November 14 at 00:29, Edited on 24 November 14 at 00:41 by Impdaddyzer0
The game invisibly keeps track of every chapter completed, for each difficulty level, in both SP and local co-op MP (not to be confused with the DM-style local competitive MP, which this game has, but is more of an afterthought), but there's nothing within the game that tells you which ones you've completed. I ended up keeping my own spreadsheet, of sorts. Along the way, I've bounced back and forth between SP and local co-op MP (which isn't split screen, by the way. It's both players together fullscreen). I've also bounced back and forth between difficulties, due to playing with different friends along the way, as well as some double controller action to finish the 3 MP-specific difficulty ones. All of the achievements are obtainable in both SP and MP, except the 3 SP-specific difficulty ones and 3 MP-specific difficulty ones. Unfortunately, none of those 6 stack in any way, so 6 playthroughs are required to get them all. Progress towards collectible-type stuff (credits, treasure chests, potions, etc) is cumulative across all game variations. My second profile has well over half of the achievements at this point, including several character-specific ones, all in MP, and most of those are achievements I popped in SP on my main profile before doing any MP at all.
One more thought. All progress is saved after the chapter results screen. Make sure you see the results screen before returning to Taleville or exiting. After beating the game on any difficulty level, Chapter Select becomes available for all difficulty settings. You can literally work your way backwards from the last chapter to the first chapter if you want to. You can do them completely randomly if you want to. As long as the necessary chapters are completed, in any order, the achievement(s) will pop.
\m/ IMP \m/ That's what it says: A horrible person. We weren't even testing for that. \m/ IMP \m/