It’s the 1980s and General Mills is making waves with a new cereal based on the world’s hottest video game: Pac-Man. But Kellogg’s is hoping to cash in on a different trend: the growing clamour among adults for healthier breakfasts. So it’s plotting a taboo-busting ad campaign that will rewrite the rules of cereal promotion and spark an all-out battle among the cereal makers to win over the health conscious.