Knowing when the trend has actually flipped—instead of chasing noise—is one of the hardest parts of trend trading. HalfTrend (HT) is one indicator to evaluate for that purpose. It draws a single trend line that switches between support and resistance, plus an ATR-based channel around it, and it marks Buy and Sell only when the internal trend state changes. That keeps signals clear and avoids the clutter of many overlapping lines.
In the Pineify implementation, price comparisons and moving averages over the amplitude lookback determine trend transitions. ATR determines channel width and arrow offsets; it is not the trend-switch threshold. When the trend flips from down to up, you get a Buy signal and the line turns into support (often shown in blue); when it flips from up to down, you get a Sell signal and the line acts as resistance (often shown in red). The ATR High and ATR Low bands form a ribbon that shows the channel around the trend line. Compare amplitude values on the same symbol and period before choosing one. The examples below describe possible rules, not tested performance.