The main screen shows animations of dice. The Roll Dice control allows you to roll the dice.
Click Set up to choose the number of dice to display on screen, the type of dice (how many sides each dice has), whether they display numbers or dots, and the number ranges for these.
Clicking Reset undoes all changes you have made, returning the tool to its default state.
Note: 6 and 9 are distinguished by a dot at the bottom of the number.