The backplate's ambient light sensor (raw counts, once a second).

Someone moving near the thermostat makes the light flicker: within a few seconds it both drops and rises as their shadow passes. Clouds change the light just as much, but steadily in one direction. A flicker, or a sudden jump such as a light being switched on, is published as a :light event %{level: counts}.

:light is one of the default wake sources, because the backplate's motion sensors can stop reporting for minutes after a long quiet spell.

Over the last 5 samples, it counts when:

• the light both fell and rose by :light_wake_flicker_pct percent or more from one second to the next (default 6), or
• it changed by :light_wake_jump_pct percent or more in one second (default 40).

Changes smaller than :light_wake_min_delta counts (default 200) are ignored, so noise in the dark doesn't count.