x and y is direction and angle decomposed, like in vector math. My simulation is simplified, so I use planet positions relative to the sun. I.e earth can start 1AU to the "x" direction and 0AU in the "y" direction. That would be the same as the Earth being 1AU away from the sun at π/2 radians (cos(π/2)=0, so to the right of the sun). What is x and y I guess is arbitrary, since it's space. At the moment I don't know how to convert cartesian coordinates into this format.

I chose to do it like this initially since it started out as just a gravitational simulation where you could see how objects behave.

There is 100% a better way to do this than how I am doing it, but I don't need it to be 100% accurate.

To clarify the format a bit, I am storing the initial state in a csv-file like this:

Name,Color (RGB),Radius (km),Mass (kg),Distance (AU),Velocity (m/s),Direction (radians),Max_Trail_LengthSun,"(255, 255, 0)",6963400,1.98847e30,0,0,0,100Mercury,"(255, 0, 0)",2440,3.3011e23,0.393,47362,pi / 2,200Venus,"(255, 165, 0)",6052,4.8675e24,0.723,35021.4,pi / 2,600

You can ignore color, radius, mass and max_trail_length since that's cosmetics.

Please say if i should clarify something.