Simple box to look up down trend

A simple box in 20 candle to monitor price

Top is the highest and bottom is the lowest of close in 20 candles.

As close is moving outside this box then the signal is up or down trend.

Code sample:
low_val = ta.lowest(close, 20)
high_val = ta.highest(close, 20)
//Create Box
box bx = na
bx := box.new(time[19], high_val, time, low_val, xloc=xloc.bar_time, bgcolor=color.new(color.aqua, 90), border_width=1)
box.delete(bx[1])