I've been puzzling over what I wanted to post for days, actually. I tried different wordings, but they all sounded stupid. So, I decided to ask directly, because it sounds least stupid. I've noticed a lot of games are labeled 'open world' or 'wide open sandbox' - most Bethesda games (Skyrim, for convenience), Xenoblade Chronicles, Terraria/Minecraft are great examples. Yet, other than relatively (and, varying degrees of) broad goals, it occurred to me that I don't really understand about what makes a sandbox a sandbox, other than broad, largely player-defined goals. I certainly don't understand what makes certain 'sandboxes' good sandboxes, for that matter.