//@version=4
study(shorttitle="BB", title="Bollinger Bands", overlay=true, resolution="")
length = input(20, minval=1)
src = input(close, title="Source")
mult = input(2.0, minval=0.001, maxval=50, title="StdDev")
basis = sma(src, length)
dev = mult * stdev(src, length)
upper = basis + dev
lower = basis - dev
offset = input(0, "Offset", type = input.integer, minval = -500, maxval = 500)
plot(basis, "Basis", color=#872323, offset = offset)
p1 = plot(upper, "Upper", color=color.teal, offset = offset)
p2 = plot(lower, "Lower", color=color.teal, offset = offset)
fill(p1, p2, title = "Background", color=#198787, transp=95)