air pollution: rm now-extraneous event

[#74611394]
air pollution: rm mask (which isn’t actually used)

[#74609396]
air pollution: add new background img

[#74609396]
air pollution: rm “lining up” of pollution particles

[#67429718]
air pollution: rm awkward baseHeading property

[#67429718]

We want to keep track of the slightly drifting long-term heading of the pollution particles, but also allow the particles to drift upward because of temperature, or to the left or right due to the wind.

The previous solution was to use AgentScript’s forward() method for every step of the particles’ motion, but the forward() method requires the direction to be kept in the “heading” property of the agent. Somewhat awkwardly, the code kept a separate property, “baseHeading” to store the long-term heading of the particle, while using “heading” as basically an argument to forward().

As a simplification I use “heading” to store the long-term heading, and use setXY() instead of forward() for motions which don’t require knowing the long-term direction of the particle’s motion.
air pollution: subtler pollution trapping

[#74775528]
air pollution: “sharpen” the trapping effect

[#74775528]
air-pollution: clarify comment re masking

[#74610516]
air pollution: rm suffix/decimal point from axes
air pollution: update colors of pollutants

[#74610516]
air pollution: make graph background white

[#74610516]
[#74611490]
air pollution: add key (legend) to graph

[#74611490]
air pollution: WIP on cars

[#74610756]
air pollution: fixup calc of wind stoppage

[#74610756]

Now that background mask has a transparent (black) background in stead of white, we need to reverse the way we calculate wind stoppage by the mountains.
air pollution: ++ extent, strength of wind block

[#74775528]
air pollution: widen road

[#74610756]
air pollution: allow multiple cars

[#74610756]
air pollution: only non-electric cars should emit

[#74610756]
air pollution: use new factory image

[#74610820]
air pollution: expand on y-label of graph (AQI)

[#75223250]