A few tweaks

This is a small update after the first release. Based on some feedback I put a proper background at the start, and did a little clarification work. I'd prefer not to over-revise this particular fanroute as it's my first one, and I think it would be great for posterity. I'm pleased that a lot of feedback points its weaknesses to being more technical stuff, as opposed to character stuff. It seems I achieved my goal! Which makes me really happy.