Definitely leaning heavily on the mind/mystery kind. I want something that forms into it's own narrative. In terms of physical puzzles, did you ever play [i]Deus Ex: Human Revolution[/i]? The hacking mini-game, I could play it all day, never got old. That's what I envision with that, but physical puzzle aren't as essential to my idea as the mential/mystery part. I feel this concept really fits in well with Bungie's desire to move us away from the "pipeline" gameplay experience they referenced at GDC and encourages players to fully take in the environment. If all you are doing, is clearing out enemies and moving on to the next objective, why take time or focus off of pressing forward? However, if you know understanding your environment might help you accomplish something else down the road or even send you on a mission no one has directed you to, then you are going to the time to look at the walls, push the buttons and explore all the nooks and crannys.