I agree about black hole, in development process was even harder to see. I added those little gray sparkles for that reason, but the issue still persists. The gravity FX is a double-edged sword: can be very useful if the black hole spawns on bottom screen, but it turns out useless if it spawns on top.
Also please note, the FXs are not random. Each planet has its own and the one which is nearest the moon, becomes active.
Thank you for the feedback and for playing, Serpent7776!