Anything goes. I'll start first.
>The Light has conquered the world with eternal sunlight.
>>55378744
Attempting to make darkness is always rendered useless as the rays of the sun pierces and burns through the fabric and materials, rendering shelters impossible.
Secrets are considered "darkness" by the Light, and thus hiding things is considered punishable by Radiance.
>>55378812
with the absence of darkness comes the absence of night, which in turn means the absence of sleep for the living.
>>55378845
those who have been punished by Radiance are marked with a brand of sunspots on their skin.
Dentists are in fact secret police whose small talk is designed to sniff out dissent. They implant listening and tracking devices in fillings.
>>55378812
The Ocean has boiled away under the Light's eternal gaze.
Solar panels occupy vast swathes of the surface world, like leaves on a tree. The unbelievable amount of power generated from them is routed to subterranean hive cities. The excess energy is used to run power hungry, unstable machines built more from theoretics than proven principles. These push science forward at a breakneck, dangerous pace; often at the cost of human life and entire hive cities.
>>55379253
The people in the underground hives are considered subhuman animals, as they can't see the glorious Light. As such, any time one "escapes" to the surface, the surface dwellers beat them back down, or sacrifice them to the Light in penance.