I had over a period of years formulated my own idea about the nature of the universe largely inspired by Conway's Game of Life
simulation. There was speculation that if the space for a Game of Life was large enough and evolved enough, the cellular automata could evolve into true life or intelligent life in their own celluar atomation universe. At some point I had the thought that the the automana didn't need the computer to exist. The mathematical definitions that defined their potential existence gave them a real existence whether we ran the simulation or not on some giant computer. The simulation was like recreating something that already exists. If we assume an infinite number of universes exist as quantum mechanics seems to suggest, then we are just experiencing one branch of a solution, one parametric path, of an immense equation with near infinite or truly infinite independent variables.
Our universe and our existence would be the same. Nothing need exist except the rules of math. You don't ask what comes below the bottom of a parabola, the same with our universe. The start is just where the rules start from a singularity. There is nothing before it because time is just a parameter that has no meaning before the singularity. Just has -1 y means nothing to the parabola y = x^2. The start of the parabola universe is at x=0 and there is nothing before it. However the Parabola Universe is not complex enough to contain sentient creatures such as ourselves. But there are infinitely more definable universe all with real existence in a sense, but then again only those complex enough to contain thinking creatures might be called/perceived as real. Given the infinite universes that then exist, there would indeed be some running simulations that create simulations of our universe, but our existence doesn't depend on those simulations being run, it merely gives those universes a window into ours.
I had started on a few occasion to put pen to paper to write these ideas down, but it appears I was beaten to the punch by Max Tegmark
and his Mathematical universe hypothesis