lightOn = False

def setup():
    size(800,800)

def draw
    global lightOn
    if lightOn == True:
        background(255)
    else:
        background(0)
    
def keyPressed():
    global lightOn

    # Option 1: Implementing a True/False toggle
    lightOn = not lightOn

    # Option 2: A True/False toggle using an if statement. Same
    # behavior as Option 1
    # if lightOn == True:
    #     lightOn = False            
    # if lightOn == False:
    #     lightOn = True