This is my son with one of his favourite toys....the marble run. Just in case you haven't seen one before, you basically just pop a marble into one of the top receivers, and it runs it's course down to the bottom. He just loves this toy. Personally, I'd get bored with it in about 5 minutes, and I'd expect most other children to have limited attention to this one too. But he just loves it. It's perfect for him. Repetative and predictable, with enough variation on the different paths down to make it interesting.
I used to feel really bad about leaving my boy to play alone. Especially when he is just staring out the window. I still feel guilty at times, but realistically, there is only a certain amount of time I can spend with him. I have a family to care for, which means dishes, washing, cooking, cleaning.... (the cleaning usually gets left lowest on the priority list unfortunately - I hate this, but I can only do what I can).
The reason I feel bad leaving him, is because I hate the idea that he retreats into his own little world, alone. I thought there was nothing going in his little mind. I am beginning to change my opinion of this.
I have been reading a book where two autistic people talk about how they see the world, and the what sort of thought processes went on inside their heads as they were growing up. I am loving it... it is so enlightening for me, and I've already learned so much from it. Since reading this, I realise that there is in fact a LOT going on inside my sons head. I - we - might not see it, but there is alot of stuff going on in there all the time. Sometimes, it is too much for him, hence why he might fixate on something else for a while. This brings him some measure of comfort and control in his life. And lets be honest, we all need that.
The ability to play alone and entertain oneself is in itself a skill. Part of my son's problem is that he lacks imagination, so when I find him investigating something - even just a repetative type of toy, it is good. This doesn't mean I should leave him to stim or stare all day. But it does mean that if I need to get things done, it's not necessarily going to be detrimental to allow him to do his own thing. Chances are, he's working out the world around him in his own way - in a way that makes sense to him. While too much of this can lead to a warped view of the world he actually does live in, a little is okay.
So if he's enjoying watching that marble run the same way over and over and over again, it's alright.... he's happy, he's busy, and I'm able to get some other things done in the meantime. When he has had enough of it, he usually comes looking for me anyway.