Mines
A grid game: flip safe tiles to grow your multiplier and cash out before you hit a mine.
Mines is played on a grid, usually 5x5, so 25 tiles. You pick how many mines are hidden, then flip tiles one at a time. Each safe tile bumps your multiplier up. You can cash out whenever you want, but hit a mine and your bet's gone.
Where the mines are
The mines are placed the moment you bet. In a typical provably fair version, the game shuffles the 25 spots using a string of floats (Fisher-Yates style: each float picks one of the spots still left) and the first spots picked become mines. A full shuffle can take up to 24 floats, more than one HMAC gives you, so the cursor runs through several HMAC rounds.
Why that's good for you
Since the grid is locked when you bet, you can check afterwards that the mines were exactly where the casino said, and that nothing moved based on where you clicked.
Real-life odds
With 3 mines out of 25 tiles, your first click is safe 22/25 of the time (88%). Two safe clicks in a row: 22/25 x 21/24, around 77%. The multipliers follow those odds, minus the house edge.