Complete the following exercises on your own: 

1. Change the maxGlobal rate of decay. You decide whether to make it faster or slower.
2.  Increase or decrease the maxGlobal rate of decay based on the user's amount of movement. Hint—recall how we tracked the user, and use that to determine how far they have gone or how fast. Use that information to set the rate of decay.
3.  Write your own custom lighting surface shader. This one's difficult, but it's worth the effort.