The game represents Pacman's quest for pills. Their consumption had many side effects, ranging from dramatic vision improvement to body transformation and addiction, leading him to chomp everything mindlessly. The ghosts represent his conscience's projection of his workmates he mindlessly chomped through earlier. When Pacman confronts his conscience, he stops chomping, leading his addicted organism to immediate destruction. Unless he's high after consuming a condensed pill, in which case he manages to defeat his conscience. It was all there in the arcade machine's setup manual, in the section of license explaining why shouldn't it be placed near to automatic medicine dispensers.