Its only function is to make darkness and light a valid mechanic for the default minetest_game. In other voxel games, darkness is dangerous because it spawns monsters. In Minetest Game, darkness just makes it more likely for you to walk into a tree.
This mod changes that in a very direct fashion: you are damaged by darkness, the darker the more damage. So craft those torches!
Current behavior
If you stand in a node with light level 7 or less, you slowly lose "sanity", represented by a hud bar with eyes. The darker it is, the more sanity you lose per second. When you run out of sanity, you get damaged instead!
Stand in bright light to replenish sanity. Sunlight is best, but directly on top of a torch should work, too.
Nice gameplay
It's cool because it force the player to play normally with torches, and not a high gamma value. Nice mod.
Sam is very scared of the dark
This kinda works like a sanity meter. You have a new "healthbar" that indicates how much time you can tolerate in the dark before drowning in eat. It makes exploring caves more dangerous because the only way to regain tolerance is by being on the sunlight. That means that if you are at the bottom of a cave and you have little tolerance left you could die while going up because you lost it all and are to deep to get sunlight. My only complaint is that the light level required for Sam to start loosing tolerance might be too high wich doesnt allow for you to have places with moody lighting, instead you must have very well lit areas to stay in during the night or underground