Raid Night

A grid of 6 columns and 5 rows. A symbol pays when it lies on the grid 8 times or more, wherever it lies, by how many there are: 8 to 9, 10 to 11, or 12 and more.

Symbols that paid clear, what is above them drops, and new ones fall in from the top. This repeats while anything pays, so one spin can pay several times.

What 8 to 9, 10 to 11, and 12 or more of a symbol pay, in bets: Breaching charge 12×, 30×, 60×; Crossbow 5×, 12×, 30×; Gas mask 3×, 7×, 18×; Field kit 1.8×, 4×, 12×; Fuel can 0.9×, 1.8×, 7×; Wrench 0.6×, 1.2×, 5×; Ration tin 0.4×, 1×, 3.5×; Scrap cogs 0.25×, 0.6×, 2.5×.

Gold never clears. 3, 4, or 5 and more gold on the grid when it has come to rest open the raid with 7, 10 or 12 free spins: about one spin in 248.

Before the free spins, a duel. Ironback (the crawler) and Nightjar (the gunship) each carry a whole number from 1 to 50, every number as likely as any other. You back one of them without seeing either number. The one that carries more wins. If you backed the winner, every win of the free spins is multiplied by the larger number; if you backed the loser, by the smaller. Each side wins as often as the other: neither is the better bet.

3 or more gold on a free spin add 5 spins, up to 40 in all.

The raid can be bought for 104× the bet: it starts at the duel with 7 free spins and returns 96.23%.

A round, raid included, pays at most 5,000× the bet. A raid left waiting for a side for 24 hours has Ironback backed for it.

The return printed here was measured, not derived: 96.55%, give or take 0.06 points, over 500 million spins and 30 million raids. The spins themselves return 54.9% and the raid the rest; a raid of 7 free spins pays 100 bets on average.