D'ni is the ficitonal base 25 number system in the hit 1997 point and click puzzle game Riven made by Cyan Worlds.

This program can convert between decimal and D'ni.

Use the Spinner in the top left to enter a decimal number that will convert to D'ni on the right.

Use the Buttons to create D'ni digits and add or remove them to the current D'ni number at the top right. The corrosponding Decimal number will show in the Spinner in the top left.

These buttons will make sense if you know the number system, but basically there are 4 "digits" that represent one through four (look in the "1s" pane). To represent five through 25 you rotate the "digit" 90 degrees and multiply by five. 25 has it's own symbol (the "X") and zero doesn't have a symbol which makes the 25 symbol needed.

For example to make 16 you would use the three "digit" rotated to denote 3 * 5 (= 15) and the one "digit" NOT rotated to denote 1. 15 + 1 = 16.

To represent numbers higher than 25 you add another "combo digit" just like in decimal. Fiddle with the Spinner to see the counting system in action.