More light in an indoor area, production bonus. Nothing crazy, just a few percent.
I thought of this when my workshop was remodeled and became well lit and I realized it was all cosmetic.
Already a thing. ;D Being in darkness comes with penalty to global work speed and movement speed.
Yes, it is, but just for one level indicating complete darkness or some light. It doesn't function as a bonus, only a penalty. I am suggesting that some areas can be better lit than other lit areas and an actual work speed bonus on production in those areas of a few percent would be logical.
There is no really bright lamps, only up to 100% (normal day light).
As i can propose, in might be normal (100, or even 105%, as TS said) work speed at day, than down to about 90-95% work speed at 50% light, and down to 50% work speed and, emm, 70% walk speed in dark. Yes, not suddenly change, but slowly, as a function of light level.
Aand, then you can place "solar" lamp at your laboratory (where is only 50% light level usually), if you want work slightly faster.
(i haven't noticed dark debuffs for now)