ok, assume i am a Dead Space n00b (because i am), i haven't played any of it, i'd like to play all of it and i have a pile of questions.... 
 
first let me list them: 
 
Dead Space 
Dead Space 2 
Dead Space Extraction 
Dead Space Ignition 
Dead Space Downfall
 
let me see if i have my facts straight first.... 
 
Extraction is a prequel to the original and was a Wii exclusive but can now be had on the PS3, right? 
Ignition is a prequel to, uh, the sequel that hasn't been released yet, right? 
and Downfall is, wait, what the hell is Downfall? 
  
and what about save file continuity?  is it safe to say that the PS3 is the only system on which you can get each of these?  and does it matter?  do the saves carry over from one game to the next?  in that most recent video, the smiley producer guy said something about getting Isaac all jacked up and ready, does that imply that progress made in Ignition will carry over into Dead Space 2?  and what about my platform of choice, the PC? 
   
basically i'd like to play every bit of it, but i'm not sure which order to play/watch all of this

i'm so confused
 
anyone?