Floody

A young hedgehog came to the pond one day, puzzled. "Sometimes I click one square," he said, "and a huge chunk of the board just opens up all by itself. Is the game broken?"

Floody laughed a big, happy, quacking laugh. "Not broken! That's the best thing in the whole game. Come here, I'll show you."

She waddled onto a fresh board and pointed with her wing at the numbers. "Every open square tells you how many mines touch it. A one means one mine is next to it. A two means two. And a zero..." She paused, eyes sparkling. "A zero means no mines touch it. None at all."

"So?" said the hedgehog.

"So if a square has no mines around it," said Floody, "then every square next to it is safe. Every single one. The game knows that, so it opens them all for you, automatically. You don't even have to click them."

She tapped a zero with her bill, and the squares around it flipped open.

"And here's the splashy part," she went on, bouncing. "If any of those new squares is a zero too, then its neighbours are safe as well. So they open. And if any of those are zeros..."

The hedgehog's eyes grew wide as he watched. The opening spread, zero to zero, square to square, rolling outward across the board exactly like Floody's wave across the pond. It kept going until it reached the edge of the empty region, where it stopped at a border of numbers, the squares that touched at least one mine.

"It stops at the numbers," the hedgehog said, amazed.

"Right," said Floody. "A number isn't a zero, so it doesn't spread any further. The wave washes open the whole empty patch, then stops right at its shore. And all of that," she spread her wings wide, "happened from one click."

"That's why Bevvy counts each empty patch as just one click," the hedgehog said slowly, remembering.

"Exactly!" Floody quacked. "A whole empty region only costs one click, because one splash opens all of it. That's also why finding a zero is such a lucky, lovely feeling. One little tap, and a whole field of the board opens up to you."