**Effect demo
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**Example programs
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**Script description**

The ranges of the random numbers are controlled by setting its upper and lower limits. | |

By replacing the color value with a random number, you can make the on-board LED randomly change its color. | |

The color changing frequency of the LEDs is controlled by the waiting time. |

**Knowledge Points
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**Use of the random number block**

The random number means that the number generated each time is uncertain and has no relationship with the one generated last time. For example, the result of rolling a dice can be considered as random since the outcome is between integer 1-6.

Several tips in using the random number block

**1） Define the range of the random number.**

- Define the two ends of the range of the random number. The range can start from a smaller number to a larger number, or vice versa. Namely, is equivalent to .

- Double-click onto enter the range directly, e.g., ，Other than using integers, a decimal or negative number is also acceptable.

**2）Display the random value. **By clicking on the block with the mouse, the random value will be shown at the upper right corner. For example, 、

**3）Random integer and random decimal. **When the two both contain integers, an integer will be selected randomly, but if there’s a decimal in at least one , a random decimal will be generated. For example,

In this sample, random numbers are selected as the values of the three-primary colors, red, green and blue. In this way, red, green, and blue colors are combined together randomly, producing a random color for the LED light.

Since LEDs do not accept decimals as its brightness, only integers are used as the random numbers in this sample.

**Extended tasks
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**Task 1**

Do not change the green and blue values, choose a random number for red, and observe the light effect.

**Task 2
**Change the script to allow the left and right LEDs on board to show different colors.

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