Twin Obelisks

How to play

1. Set your entry in the panel on the right. It is the amount each separate selection costs.
2. Choose a sector by its number, or one of the two colour bands, or odd against even. You may place as many selections as you like in the same round, and each one is charged separately the moment you place it.
3. Press release. The ring turns, the pointer stops in one sector, and every selection you placed is settled on its own.
4. A sector selection pays its published multiple, and a band or odd-even selection pays 1.9 times the entry. Clear returns everything you have placed if you have not released yet.

The rules

Choose a whole sector by its number, choose one of the two colour bands, or choose odd against even. Set your entry, place as many selections as you like on the same round, and release the pointer. Every selection is settled independently once the pointer stops, and the round total is the sum of all of them.

If this is your first board

Start with a colour band. It resolves roughly half the time, so you see a lot of rounds quickly and get a feel for how streaks look. A run of six identical results in a row is not evidence that the board is due to switch: the pointer has no memory, and the next release is exactly as likely to repeat as it was the first time.

Pay table

Every figure below is computed from this board's own settings, not typed in by hand.

The formula

The maths behind it

With N equal sectors, one named sector comes up with probability 1/N. This board pays a named sector at a multiple slightly below N, and pays a colour band or an odd/even call at slightly below double. That gap is deliberate and it is published: it is what keeps a long session drifting downward instead of staying flat, and it is the single most useful number to understand about any board of this shape. Nothing here is worth money, so the drift costs you nothing but it teaches the shape of the curve exactly.

Where it comes from

Pointer-and-sector devices are one of the oldest randomising tools people built. A ring divided into equal parts and a pointer released with enough force to forget where it started gives a result nobody can steer. Mathematicians took an interest early precisely because the device is so easy to describe: if the sectors are equal and the release is genuinely uncontrolled, every sector is equally likely, and that is a rare thing to be able to say with confidence.

If this is your first board

Start with a colour band. It resolves roughly half the time, so you see a lot of rounds quickly and get a feel for how streaks look. A run of six identical results in a row is not evidence that the board is due to switch: the pointer has no memory, and the next release is exactly as likely to repeat as it was the first time.

Other boards in this family

Open the board Sun Disc