This lesson uses the @boardname@ to measure a student's reaction time in completing a circuit path on a cardboard pad. The student's reaction time is measured in both a distracted and an undistracted environment.
Test the reaction pad by putting one hand on the ground pin (**GND**) and one hand on the **P0** pin. This completes the circuit and starts the timer on the @boardname@ after an initial 3 second count down.
Once the timer starts, wait for the LED screen to light up and then press the **GND** foil with one hand and and the **P1** foil with the other. This completes the circuit and shuts off the timer.
In order for **Reaction Time** to track the speed of a a player's reaction, we need to add variables to keep some data. We initialize (assign, or set) the variables to some starting values. The variables needed are: `start`, `end`, `false_start`, and `running`. Set the values of variables `start` and `end` to `0`, which means no time elapsed. Then set the value of the variables `false_start` and `running` to `false` to say we haven't started yet.
We need to register event handlers that will execute whenever the user presses down on the **GND** pin with one hand, and presses pin **P0** or **P1** with the other hand, which completes the circuit. Our event handlers are two ``||input:on pin pressed||`` blocks, one for **P0** and the other for **P1**.
Add the ``||input:on pin pressed||`` blocks to your code:
We need a countdown timer that shows the seconds counting down when pin **P0** is pressed. Let's insert three ``||basic:show number||`` blocks to visually display the countdown sequence: **3**...**2**...**1**. Next, add a ``||basic:clear screen||`` block to clear the numbers from the screen. Modify your code so that it looks like this:
Let's add a random starting time after pin **p0** is pressed. Include the ``||math:random||`` block in a ``||basic:pause||`` at the bottom of the event block like this:
The reaction time will begin if no false start is detected (pin **P0** pressed at the wrong time). When the reaction time starts, a LED is randomly plotted at some the x and y coordinate on the display. Add in the blocks contained in the ``||logic:if then||`` that show the reaction time:
Add some code to detect when the player presses the **GND** foil with one hand and the **P1** pin with the other. This code detects the circuit connection and shuts off the timer. Also, add code to have the @boardname@ read the time in milliseconds from when the timer starts and the circuit is completed. This code also detects if there is a correct reaction or false start if pin **P1** is pressed.
Let's display one of two images if pin **P1** is pressed. The first image displays if the player correctly completes the circuit between **GND** and **P1**. This means that a correct reaction occurred to complete the circuit with pin **P1** pressed after the randomly generated LED appears.
The second image displays if the player completes a circuit between **GND** and **P1** but on a false start. A false start is detected if the player completes a circuit if pin **P1** is pressed before the LED randomly appears at its random x, y coordinate. Modify the code to include the actions for the pin **P1** event:
After the students have finished their experiments. Have them play the game with a friend (using the **P2** pin) and have some contests to see who is the quickest on the draw.
