Dancing LEDs in both directions

Let's create another illusion program where the light will go from USER0 to USER3. Then, instead of starting again from USER0, it travels back in the opposite direction from USER3 to USER0. We will follow the turning on of the LED sequence: USER0 -> USER1 -> USER2 -> USER3 -> USER2 -> USER1 -> USER0, and so on. This will look like the LED is traveling till the edge and then bouncing back. Type the previous danceLEDs.js program as it is. Change the following line in the glowUser3() function:

tempTimer = setTimeout(glowUser0, glowTime);

Replace it with the following line:

tempTimer = setTimeout(glowReverseUser2, glowTime);

Then, insert the following code after the glowUser3() function ends and before the exitProgram() function starts. Save the modified code as danceLEDs2.js and run it. You should see the LED pattern moving from USER0 to USER3 and then back to USER0:

function glowReverseUser2()
{
  b.digitalWrite("USR3",b.LOW);
  b.digitalWrite(...