Hot Gems Xtreme Slot by Playtech

The grid starts short and grows. Six reels, four rows to begin with, which works out to 4,096 ways to win. But any win can push the reels up a row, and each extra row multiplies the ways: 15,625 at five rows, then 46,656, then 117,649, and 262,144 once all six reels stand eight symbols tall. That top figure is 8 to the power of 6, and it's where the growing-reels idea earns its keep. Safety Levels matter here too, because they hold your progress between spins, so the height you've built can carry over or climb again rather than always collapsing back to four rows.

Three symbols do the demolition work that keeps the grid moving. TNT bundles detonate and blow out chunks of the reels. Giant symbols land oversized, covering several cells at once. And a flaming "?" mystery drops in to reveal a random symbol. The blue diamond Wild fills in for the paying symbols, while the top payer is a white-bearded miner in a brown hat, grinning out from the reels beside cut gemstones in gold, red, green, blue, purple, pink and a clear white diamond.

Free games come from the gem chests. Three or more trigger the round, and six or more hand you up to 25 spins. There's no fixed cap once you're inside, since extra spins keep coming, and the reels still grow through the whole feature, so the ways count can stack right up while every spin is free. No buy option, though, and no jackpot on this base version. If you want jackpots, that's the separate PowerPlay Jackpot edition. The growing reels plus giant symbols plus that swelling ways count is what builds toward the 10,000x ceiling.

The setting is a cheerful cartoon mine deep underground. Rocky brown walls braced with wooden beams and ladders, a hanging oil lantern, a shovel, mine carts spilling over with coloured gems. It shares the jolly-miner mascot with Hot Gems Cash Collect, but the mechanic is a different animal: that one collects coins, this one just keeps stacking rows.