Enter a probability or arithmetic expression that evaluates to a probability. Now think of a number, 1 to 20. A grid of numbers will appear and your number will be lit up with the given probability. Why's that useful? Say you owe me $7 but only have a twenty. Give me $20 with 7/20 probability. Perfectly fair in expectation!

Recent changes:
Name change. Added restaurant bill-splitting syntax. Background color cycles (to verify button press). Soft keyboard doesn't hide screen elements.