Mighty Hat: Mine O' Mine Slot by Playtech

Down in a warm red-rock mine cavern, hanging lanterns throw amber light across a board of prospectors and gold-filled carts. A blonde miner girl in a lamp-helmet tops the paying symbols, above a cigar-chewing old prospector, a bandana-wearing dog and a set of mining tools, with purple amethyst crystals and A-K-Q-J-10-9 royals underneath. The reels sit in a carved red-and-gold surround, four jackpot plaques bolted across the top, and a grinning purple genie-hat mascot peeks in from the bottom-left. Wins pay 243 ways, matching from the left on adjacent reels with no fixed lines, and a lantern Lamp is the wild. It covers everything except two symbols: the gold-filled mine cart and the mine stone.

The middle reel is the one to watch. A second, special Lamp wild only ever lands on reel three, and when it shows up it hands you one of four features at random. It might be a Respin, a single respin with some reels held and a multiplier riding every ways-win while it runs. It might crack open a Treasure Chest holding up to five prizes, any mix of cash, jackpots, Free Games or the Mighty Hat feature itself. It might start Free Games, a free-spins round that can retrigger. Or it opens Mighty Hat.

Mighty Hat is the hold-and-win one. Nine spins, the special Lamp becomes a gold border, and mine stone symbols build borders around the reels as they land: empty upgrades to silver, silver to gold, gold to red, and every border stays locked for the full nine. Four fixed jackpots sit over all of it, the Mini and Minor at 20x and 50x total bet, the Major at 500x and the Grand at 1,000x, and any of them can fall straight out of that Treasure Chest. No buy button and no ante, so that middle reel is the only way in to any of it.