I've been building a room system for Atom. Full writeup on that is coming, but one piece of it pushed me into rewriting temperature first, and that's what this post is about.
The room system needs players to have a real reason to enclose space. Walls, a door, a roof. Not because houses look nice, I wanted to think what an enclosed space could actually do for the person inside it. The strongest answer kept being heat; that sent me back to the old temperature system, which I already didn't love.
What was broken
Old temperature only looked at biome and time of day. Walls didn't exist to it. You could stand in a blizzard under a roof with a fire going and the system would still call you freezing, because biome said snow.
That's fine if temperature is flavour. It's not fine if I want specific biomes to be a place you have to prepare for. Frozen Peaks are what I used as the test case. In the old system you can walk through them in leather and barely notice. I want them to be the place you don't get to wander into. You go prepared or you don't go up there.
The new model
Walls block heat exchange now. A closed door keeps heat in better than an open one. Same with trapdoors, vents, glass panes. Panes always leak a bit more than walls.
Heat sources warm the surrounding air. A campfire in a closed room increases the ambient temperature over a minute or so. Open the door and the warmth bleeds out fast. Close it and it climbs back. Bigger rooms take longer to warm and hold steadier once they do.
Outside, biome still matters, and so does the time of day, weather, and what's overhead. A tree canopy stops the rain hitting you. A cave cuts the weather off completely. Thunderstorm with nothing over your head, you'll feel it.
Get soaked and wet clothes pull you down ~6 degrees. Rain soaks you. So does standing in water, swimming a river will do it. A fire dries you faster than waiting. So does a warm room.
Same model the game runs. Pick a scenario. Full climate explorer has every input.
Moving matters now
Sprinting warms you up in the cold now. Same sprint in a desert cooks you faster than walking would. Standing still is the worst thing you can do in cold. You're losing heat and putting nothing back. Jumping is a small burst on top of whatever else you're doing.
None of it is dramatic on its own. I also slowed the overall stress meter down while I was in there, so cold and heat both build more gradually. Out on the peaks the two changes stack into a few extra minutes before stress starts to bite. Usually enough to get back to base.
Things I cut / changed
There was an ItemHeatSystem for a while that tracked heat on every item you were holding. It drove a penalty when you carried something hot. Cool on paper. In practice it broke item stacking, because two of the same item with the slightest temperature difference wouldn't stack, and inventories filled up with near-duplicates. Got in the way more than it helped, so cut it.
The one piece that was important, hot tool molds drifting back toward ambient, got rebuilt as an action: you cool filled molds at a water source now instead of waiting it out.
Wind chill I considered and parked. I like the idea, may come back to it, but for now I want a model that's simple enough to read at face value.
What you see in game
I dropped the temperature number off the action bar. There's a word now. Comfortable when you're fine, Cold or Warm when you should pay attention, Freezing or Burning when you need to act. Spend long enough outside Comfortable and you slow down. Push it further and tools get sluggish, hunger drains faster, and eventually you take damage. A warning bar comes up before the damage point so it isn't an ambush.
Armor helps against cold. Leather is best. A full set beats just a chestplate. Heat cares about armor too now. Leather reflects the sun and helps in the desert. Metals bake you. Full iron in a desert is worse than nothing.
Back to rooms
Now that temperature knows about walls, rooms have something to do. The frozen peaks become somewhere you can live if you're willing to build for it. Full room system post is up next.
Easiest way to mess with the new temperature live is in the next playtest.