that's a 12L bucket. average lung capacity is 6 liters. every breath he breathes out, the air gets stored in the bucket. then he breathes it in again. he's not breathing any fresh air, just his own breath.
this is also why you die from cheap diving masks
if you have an oled display, then if a video game is brighter it costs more energy because the LEDs turn on more.
if have an lcd display, there's a backlight that always has the same brightness and crystals blocking the light, which makes the image. meaning a brighter scene doesn't take more power, since the backlight doesn't use more energy.