What do you think about when you meditate?

One is supposed to clear the mind completely after allowing the rush of ideas to run its course. Once many years ago however I thought it would be a good idea to create an "operating system" for my mind with a front page and interactive visual stimuli that would make it easier for me to access things if I were lucid dreaming (gamers do that more) and therefore I needed representations for everything going on in my head, indeed sometimes in sleep I am able to reach it.