//@version=6
indicator("Workshop 03 Stretch", overlay=false)
length = input.int(20, "Reference bars", minval=2)
threshold = input.float(2.0, "Distance", minval=0.1)
center = ta.sma(close, length)[1]
spread = ta.stdev(close, length, true)[1]
z = spread > 0 ? (close - center) / spread : na
plot(z, "Distance in deviations", color=color.blue)
hline(0, "Reference", color=color.gray)
hline(threshold, "Upper distance", color=color.gray)
hline(-threshold, "Lower distance", color=color.gray)
lowExtreme = z < -threshold and barstate.isconfirmed
plotshape(lowExtreme, "Low extreme", shape.circle,
    location.bottom, color=color.orange, size=size.tiny)