I wanted to see how quickly an Arduino could react to the LED on the reaction timer game which I built a few months ago. I set up a simple LDR circuit to detect the light emitted from the LED on the game and then a servo to react and push the button. Have a look at how the test went in the video, or read up on the circuit and the code used in the video in my blog post - https://www.the-diy-life.com/how-fast-can-an-arduino-react-tested-using-my-reaction-timer-game/ What You Need For This Test: Arduino Uno - https://amzn.to/2XwmXAa LDR - https://amzn.to/2YITHa1 Resistors - https://amzn.to/2yrVCot Micro Servo - https://amzn.to/380rddp Optional LED - https://amzn.to/2zOOPGa If you have any ideas or suggestions for Arduino or electronics projects or tutorials, let me know in the comments section. I'm always looking for new ideas.