Joker's Vault Slot by BF Games

The reels sit inside a Greek-temple courthouse facade, columns and pediment in flat comic-book ink, with the city skyline at dusk fading from cobalt to pink behind it. Cartoon dollar bills drift across the background while the "POW"-style logo bursts in red and yellow. Heist roster on the high-pay symbols: a cigar-chomping director, a femme fatale in green, a wide-eyed cop yelping "HUH?" next to a donut, a money sack, and a red getaway van. Royals A/K/Q/J handle the low end, drawn in pastel pinks, purples and greens with heavy black outlines, no dice pips on this one, that's the sister title.

The tumble is where things get unusual. After every win the matched symbols clear, new ones drop in, and the multiplier ladders up x1, x2, x3, x4, x5, x6 and onward as long as the chain keeps going. What sets this apart from most cascade engines is that any Vault scatters sitting on the grid also disappear during a winning cascade. Most games freeze scatters in place while tumbles resolve around them, here they get swept up with everything else, so a hot cascade chain can actively eat the bonus trigger you were collecting. It cuts both ways: clean wins also reset your shot at the Pick and Win.

Wilds only appear on reels 2, 3 and 4, and only in jack-in-the-box form. When the box pops on a winning line the Joker face inside expands to fill the whole column. The expand fires once per spin though, if a wild lands again during a later cascade step it stays a single tile.

Land three Vault scatters on reels 1, 3 and 5 and the heist mini-game opens up. Three closed safes shuffle, you pick one, and you get either nothing, a small prize between 5x and 20x, or a large prize ranging 25x, 30x, 50x, 100x, 200x, 300x or 500x your stake. The cascade multiplier doesn't carry over into the pick, so a long chain that triggers the bonus mid-tumble doesn't boost the safe payout, the multiplier resets when control hands back to you.

There's no buy bonus, no ante, no jackpot ladder. The top of the math is 4230.75x and it comes from compounding cascade multipliers and a lucky safe pick, usually in the same spin. If you prefer the same engine with dice-pip royals instead of standard letters, BF Games shipped Joker's Vault Dice three months later with identical math.