How to play
- Set your entry and press deal. One card goes to you and one to the house.
- The higher card wins even money. Suits never matter, and an ace is the highest card.
- If the two cards are level you choose. Withdraw half returns half your entry and ends the round. Raise adds a second amount equal to the first, three cards are set aside, and one more card goes to each side.
- After a raise, a card that is higher or level wins even money on the raise while the original entry comes back. A lower card loses both.
- Raising is the better of the two choices and the guide below prints both published figures so you can see by how much.
The rules
Cards here carry numbers only, in four colour families, with no faces and no suits. On a higher-or-lower board you see one card and call the next; a correct call advances you a step and grows the running multiplier, a wrong call ends the round. You may collect at any point. On a memory board, turn two cards per move; a matching pair stays face up, and clearing the board within the move limit scores.
If this is your first board
Take the four-by-two memory board first. Eight cards, four pairs, five moves, and every mistake is visible immediately. On higher-or-lower, remember that collecting early is a real choice and usually the mathematically better one: the multiplier grows more slowly than the chance of the chain breaking.
Pay table
Every figure below is computed from this board's own settings, not typed in by hand.
| Selection | Probability | Pays |
|---|---|---|
| You > House | 46.30% | 1:1 |
| You < House | 46.30% | — |
| Level cards | 7.40% | raise or withdraw |
| Raise and continue · Board margin | — | 2.88% |
| Withdraw half · Board margin | — | 3.70% |
The formula
level cards = (6 × 4 − 1) ÷ (312 − 1) = 7.40%
after a raise, a level card still wins the raise, which is what makes raising the better choice: 2.88% against 3.70%
On a tie
| Response | Board margin | Better response |
|---|---|---|
| Raise and continue | 2.88% | Yes |
| Withdraw half | 3.70% | No |
The maths behind it
On higher-or-lower with a top card of H, seeing a card of value v makes "higher" correct for (H − v) of the H values and "lower" correct for (v − 1). The best call is whichever side holds more, and against a low card that edge is large. Chaining calls multiplies the probabilities, which is why a five-step chain is far less likely than it feels: five calls at 70% each land together only about one time in six.
Where it comes from
Numbered cards are among the oldest portable randomisers, and the two mechanics here are the two oldest questions you can ask of them. Is the next one bigger or smaller than this one, and can you remember where you saw its twin. Both questions predate any formal theory of probability, and both were used as teaching devices long before they became pastimes.
If this is your first board
Take the four-by-two memory board first. Eight cards, four pairs, five moves, and every mistake is visible immediately. On higher-or-lower, remember that collecting early is a real choice and usually the mathematically better one: the multiplier grows more slowly than the chance of the chain breaking.
18+
18+ only. Stratosphynx offers free simulations of online casino games for entertainment and learning. There is no real money anywhere on this site, nothing of value ever changes hands, there are no prizes and there is no way to cash anything out. Virtual points have no monetary value and cannot be exchanged. Please play in moderation.