Dr.Franken's Lab 777Jackpot Slot by BigPot Gaming

Ten percent of every bet goes into a shared progressive pool. That pool feeds three jackpot tiers - MAJOR at 777x, MINOR at 77x, MINI at 7x - though each tier caps at 50% of whatever the reserve holds at the time. Three golden mini-slot-machine symbols during the base game trigger one of those tiers. The 777 Jackpot symbols only appear outside free spins, so the bonus round and the jackpot chase are mutually exclusive paths.

Walking Wilds are the base game engine. A green biohazard Wild that lands in a winning combination doesn't disappear - it stays on the grid and shifts one position left on every subsequent spin until it either stops contributing to a win or walks off reel 1. Multiple Walking Wilds stack on the same position if their paths overlap, and a Random Event can fire at any point during the base game to convert high-value character symbols into additional Walking Wilds mid-spin. Zombie hands and twisted graveyard crosses border the reels against a purple-black sky, with the three cartoon portraits - a grinning brown-haired scientist, a blonde woman, a bearded man in a long coat - filling most of the upper paytable.

Three scatters on reels 3, 4, and 5 award 8 free spins, or you can buy in directly. Inside the bonus, the Random Event stops being random. It fires every single spin as long as at least one high symbol is present on the result, converting those symbols into Walking Wilds. Eight spins of continuous Wild generation and leftward migration means the grid accumulates Wilds faster than the base game can. No jackpot symbols appear during this round - the 777 system is strictly a base game feature.

The quirky cat-dog hybrid creature sitting mid-paytable and the horror-comedy art style give the whole thing a lighter tone than the Frankenstein label suggests. Walking Wilds that persist and stack across consecutive spins are the one mechanic doing all the work here, in both modes - the free spins just remove the randomness from their generation.