I thought I read somewhere that when the battery power got low, there would be an icon that said so. Last time I was playing Tetris I didn’t see one. I went to go play another game a few days later and it shut down after the title screen of a game. I changed the batteries and lo and behold it worked again, and the shades of red seemed brighter than before. I just thought that it would tell me when the batteries are low, or was that icon thing just a figment of my imagination?

Yes, it’s there. Not sure if all games have it and where, though. You can press “W” in Reality Boy to simulate low batteries to see the indicator.