drawBackground method
Draws the Background
It's size is "big enough" to cover the screen it's centered and rotated at the same speed as the star layer
Implementation
void drawBackground(Canvas canvas, Size size, SpaceViewModel viewModel) =>
_imageMap["stars"]?.drawRotatedSquare(
canvas: canvas,
size: viewModel.backgroundSize,
offset: viewModel.centerOffset,
rotation: viewModel.backgroundRotation,
paint: standardPaint);