import turtle
t=turtle.Pen()
turtle.bgcolor("black")
sides=2
colors=["red","yellow","blue","orange","green"]
for x in range(270):
t.pencolor(colors[x%sides])
t.forward(x*2)
t.left(360/sides+1)
t.width(x*sides/150)
请问 t.pencolor(colors[x%sides])是什么意思啊?尤其是(colors[x%sides])