In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.
// || Function to draw base lines on chart.
int _base_t = time + int(change(time) * _length/window)
int _start_t = time - int(change(time) * _length)