Fair play

Every roll is decided before you play, by a secret seed the website shows you only as a fingerprint. Change the seed whenever you like: the old one is then revealed, and every roll made with it can be checked by hand.

How a roll is made

Your server seed is 64 random hex characters, kept secret. Its SHA-256 fingerprint is shown to you before any roll.
Each roll is HMAC-SHA256(server seed, "client seed:nonce"). The nonce counts your rolls with that seed: 0, 1, 2…
The first 13 hex characters of that, as a number, divided by 16¹³, give the roll: a number from 0 up to 1.
In the upgrader you win when the roll is under your chance.

Coinflips and the jackpot

These are between players, so each flip and each jackpot round has its own seed instead of yours. Its fingerprint shows from the moment it opens, and the seed itself once it ends, so anyone can check the result.

CoinflipThe roll is HMAC-SHA256(flip seed, "joiner's Steam ID:flip number"), read as above. Under 0.5 lands Light, 0.5 and over lands Blight.
JackpotThe roll is HMAC-SHA256(round seed, "pot total:round number"), read as above. The winning ticket is the roll times the pot total, rounded down. Every CC put in is one ticket, counted through the entries in the order they came in.