The inside-out universe

There are a lot of different ideas that I like, but one particular theme seems to reappear time and time again. I've tried to put it into words a few times, and this is the closest I've come: it's about building a universe from the inside.

When you work with a system enough, you learn and internalise its rules and resources. Maybe the rules of physics, or the tools of Photoshop, or the irrefutable tao of Rails. You learn how to combine resources and manipulate rules to make and do whatever you want. Eventually you become so familiar with that system that it becomes second nature. You no longer think "I'm going to use Photoshop to resize this image"; that would be like saying "I'm going to use physics to go to the park". You just resize the image. You live in the universe of Photoshop as much as you live in the physical universe, and you're building things using the rules of that universe.

More recently, one of those things you can build is a new universe, with its very own set of rules. Of course, societies, languages, games and so on have existed for ages, but they're all built from people and behaviour and tend to be hard to design. But with a computer you can build a universe easily, a consistent universe that follows the rules you decide on.

But when we create a computer program we have to step outside it, and build our amazing new universe while living in the drab universe of squiggles in a code editor. But what if it didn't have to be that way? What if you could create a universe-creating universe where the tools you use to build it aren't accessed from the outside, but from the inside?