Amid Tokyo's glittering lights, this building remained darkened to conserve energy Friday. It wasn't the only one. Much of the city -- including its usually vibrant entertainment district -- went black as Japan struggled not only with catastrophe at a nuclear plant, but also with an energy crisis. Rolling blackouts have hit Tokyo and other Japanese cities since the earthquake. No one knows how long they might last. Many have fled the capital for regions further south in the face of uncertainty stemming from the ongoing battle to prevent a meltdown at the Fukushima nuclear facility up the coast.