Velvet Vault: crack the safe, dodge the onyx

Rocco peers round the edge of a steel vault door, a diamond held up to one eye like a jeweller's loupe and a grin that says he knows exactly what he is doing. He wears black gloves and a purple waistcoat, which tells you all you need to know about his line of work. Velvet Vault, from the Nocturn Originals range by Nocturn Play, is a mines game, and you can play Velvet Vault free here with no download and no sign-up.

The rules of the mines game

The board is a 5×5 grid of velvet tiles, 25 in total. Before each round you choose your bet and how many mines to hide among the tiles, anywhere from 1 to 24. Press Bet, then open tiles one at a time. Every diamond you find raises the multiplier and drops another gem into Rocco's loot sack. Hit a black onyx mine and the round is over, bet lost.

The key button is Cash out. Press it whenever you like to collect your bet multiplied by the current multiplier. If you find every diamond on the board you are paid automatically, and the same happens if the next diamond would push the multiplier past the 10,000× maximum.

Handy buttons

• Pick random tile opens a tile for you, if you would rather not choose.
• In Auto mode you mark the tiles to open on the board, and the game repeats that pattern for as many rounds as you set, with stop rules on profit or loss.

Choosing the number of mines

This is the decision that defines your session. With one or two mines, almost every tile is safe and the multiplier creeps up slowly; you can open a lot of tiles before cashing out for a modest sum. With fifteen or twenty mines, each diamond sends the multiplier jumping, but every click is a real gamble. The more mines, the faster it climbs.

The Velvet Vault demo is ideal for finding your comfort zone. Try ten rounds with 3 mines, cashing out after five diamonds each time. Then ten rounds with 10 mines, cashing out after two. Compare how often you get to the cash-out and what it pays. You will quickly see that there is no right answer, only a trade-off you choose.

Seeds and fairness

The whole round – where every mine sits – is drawn by the server the moment you bet. A fingerprint of the seed is shown on screen straight away, and the seed itself is revealed when the round ends, so you can compare the two in the Fairness panel and confirm the board was not changed while you played. It is a reassuring detail in a game where every click feels personal.

Playing on a phone

Twenty-five big tiles are perfect for a touchscreen, and a round can take ten seconds or two minutes depending on how brave you are. There is no bonus round or bonus buy: the tension comes entirely from deciding when to stop. That makes it a good free game to practise discipline – set yourself a cash-out rule and find out if you actually stick to it.

Demo credits are virtual and have no value. The same game runs for real money at the casinos below.