In a (fairly) recent blog post, the always awesome auntie pixelante waxed poetic about how Bubble Bobble designer Fukio Mitsuji used "visual information to help the player understand the rules of a game."
Specifically, she focused on how Mitsuji explained, visually, using the giant frying pan seen in the screenshot below, the behavior of the game's fire/flame bubbles.
"Players pop the bubbles and the flames fall down to the wide, flat surface of the pan, which then catches fire--like cracking an egg and dripping it into a frying pan to sizzle," she writes. "The enemies that inhabit this stage bounce diagonally through the air; when they come down they touch the fire, pop into the air and come down as food that the players can gather. The word “POPCORN” written on the screen makes the metaphor complete."
If you're interested in game design in general and Bubble Bobble in particular--and who isn't interested in the latter?--I'd highly recommend reading the rest of pixelante's post (here).