Replicating the look of a tube monitor essentially requires introducing imperfections into the picture. Phosphors have a tendency to bleed outwards, creating a soft edge or glow around objects on the CRT screen. 240p images were displayed in 480i on NTSC TVs, creating alternating black scanlines with every video line. There are fascinating sites out there dedicated to properly handling video signals with scan converters and video processors, but those can cost hundreds or thousands of dollars. Our solution: fake it with software.
With every Mother/Earthbound game of course.