# indie:lang_version = 5
from indie import indicator, Var, plot, color
from indie.algorithms import Sma
from indie.math import cross_over

@indicator('Highlight Crossover', overlay_main_pane=True)
@plot.background()
@plot.line(color=color.LIME)
@plot.line(color=color.MAROON)
def Main(self):
    cross_over_index = Var[int].new(0)
    
    sma30 = Sma.new(self.close, 30)
    sma15 = Sma.new(self.close, 15)

    if cross_over(sma15, sma30):
        cross_over_index.set(self.bar_index)

    alpha = 0.5 / (self.bar_index - cross_over_index.get() + 1) ** 0.6
    return plot.Background(color=color.TEAL(alpha)), sma15[0], sma30[0]