Looks like I need your help, everyone. I'm trying to remember the author and the name of a book or series I read as a kid. I can remember a few things about it, but I'll need your help with the rest.

The book was actually, from what I remember, a series of children's books, each one different from the last. Meaning something like the main character and focus would change, but it was about a small group of kids that all lived in the same area. From what I remember, the three main characters were a boy, his girl neighbor, and the girl's little sister. Each of three books changed the main character to one of them.

Now the books would be what you would call science fiction today, though that's not how I thought of them at the time. The books were really about computers and unknown science and the possibilities opened up by technology. From what I remember, the computers in the book were something like the Apple I, the Apple II, IIe, III, C64, or something like that. I think at the very least the younger sister's computer had a personality, and it chatted with her through text and a command parser.

I think this is in the third book, but the little girl is able to program the computer to teleport her to the Moon. She zips up there and looks down at the Earth and thinks how blue and small it looks like from up there. After she figures out how to get back down to Earth, she later visits the Moon whenever she needs some quiet and isolation to think.

Now this could be the same series, maybe not, but there is another section of the book/series where there are invisible threads that string throughout reality. I remember this section being in a forest or among a large group of trees. The main character is told that these are the threads that hold together reality, and that they are normally invisible to people. But she can sense them, and she is able to program the computer so that she is able to pluck the strings of reality and therefore alter the world and reality around her.

The only other thing I can remember is that I read the book in elementary school, or middle school at the latest. This would have been about 1991 - 1995, so the book would have to have been published by then.

Any suggestions on the title, series, or author?