Mermaid Mighty Reels Slot by Light & Wonder

The headline mechanic is the upper grid. Three extra rows sit dimmed behind a gold lattice above the main 5x3, and when the Mermaid wild lands on a reel she expands top-to-bottom and powers those rows on - turning the field into a 5x6 for the rest of the spin. The trigger is the wild itself, not a separate scatter or random event, so every Mermaid landing is also a grid event.

Cash collect runs alongside it. Green coins carrying fixed values from $0.50 up past $10 drop onto the reels during normal play and just sit there doing nothing until the Mermaid wild expands. Her expansion is the collect signal: every visible coin on screen gets swept into the spin total, then the cash positions repopulate with fresh values for the next round. The pacing means a quiet base game can flip into a chunky win the moment she shows up on a reel loaded with coins.

Free spins come from three or more of the purple octopus scatters, retrigger on the same condition, and run the same Mermaid-plus-upper-rows logic with a different music bed. Light & Wonder caps total potential at 2,064x, and the volatility runs low - a deliberate choice for a mechanic that already trickles cash through the base game rather than hoarding it for a bonus.

BONU$PLAY is the UK Arcade buy option, split into two prices. The cheaper tier guarantees a minimum number of trigger symbols on the next spin (you might get more, you might get exactly the minimum); the pricier tier locks in an exact count. Each press changes the stake itself rather than charging a separate fee, which is the standard UK compliance route. There's also a Premium Play toggle above it for a higher-stakes mode, and a Gamble dial that offers 2.5x or 5x odds on any winning spin including free spin wins, with a max-gamble ceiling to stop infinite doubling.

Visually it's a cartoon treasure-cove setup: a heavy gold filigree archway holds the reels under sunlit blue water with bubbles drifting past, and the auburn-haired mermaid mascot stands to the right of the grid in her crown and green tail, watching the action. Premium symbols are jewel-stuffed treasure chests, ornate clam shells and gold anchors; lows are blue-and-gold A/K/Q/J/10 royals. The whole engine is a reskin of Secrets of Memnon - same expanding-wild collect mechanic, swapped from desert gods to underwater fantasy.