Tinkercad has made an online simulator for Arduino. This allows you to play around with basic components and try out your code without having to solder anything. This is especially good for group or homework projects where you do not neccesarely have access to the hardware all the time. You can even copy paste examples from the Arduino examples library directly into the simulator to test them out. To use it you need to create an account on tinkercad circuits: and the create a new project. You can also duplicate the project below. It creates a chase with a potentiometer and an neopixel strip. The speed is controller by the potentiometer using a delay(),