sma 9/20 cross

This Pine Script is designed to visualize the crossover between two Simple Moving Averages (SMAs) on a chart: a fast SMA (9-period) and a slow SMA (20-period). The script will dynamically adjust the background color based on whether the fast SMA is above or below the slow SMA.

Key Components of the Script:
Inputs for SMA Lengths:

The script allows you to adjust the lengths of the two SMAs by inputting values for smaFastLength (default = 9) and smaSlowLength (default = 20). These lengths define how many periods (candles) the SMAs consider when calculating the moving averages.
SMA Calculations:

The script calculates two SMAs using the close price:
smaFast is the 9-period SMA.
smaSlow is the 20-period SMA.
These are calculated using TradingView’s built-in ta.sma function, which computes the simple moving average for the given period.

Background Color Logic:

The background color is dynamically updated based on the crossover condition:
Green background: When the fast SMA (smaFast) is above the slow SMA (smaSlow), indicating a bullish trend.
Red background: When the fast SMA is below the slow SMA, indicating a bearish trend.
The bgcolor function is used to change the background color on the chart. The transparency of the background color is set to 35% using color.new(color.green, 35) or color.new(color.red, 35).
Plotting the SMAs:

The two SMAs are plotted on the chart for visual reference:
The fast SMA is plotted in lime green (color.blue).
The slow SMA is plotted in red (color.red).