"""
Layered Area Chart
------------------
This example shows a layered area chart.
"""
# category: area charts
import altair as alt
from vega_datasets import data

source = data.iowa_electricity()

(
    alt.Chart(source)
    .mark_area(opacity=0.3)
    .encode(
        x="year:T", y=alt.Y("net_generation:Q", stack=None), color="source:N"
    )
)
