Weather changes on time; repeat rolls lengthen the spell

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

game.py

@@ -1563,6 +1563,7 @@ def tick(world: dict, now: float, rng: random.Random | None = None) -> bool:
         _happenings_hour(world, city["last_tick"], rng)
         _city_hour(world, city["last_tick"])
         changed = True
+    changed = advance_weather(world, now, rng) or changed
     changed = _happenings_tracks(world, now, rng) or changed
     construction = city["construction"]
     if construction and construction["labour"] >= construction["needed"]:
@@ -2134,6 +2135,30 @@ def _roll_weather(world: dict, now: float, rng: random.Random, current: str | No
     return _pick(SEASON_WEATHER[season(world, now)["index"]], rng)
 
 
+def advance_weather(world: dict, now: float, rng: random.Random) -> bool:
+    """Change the weather when its spell ends. Returns True if it changed."""
+    weather = world["city"]["weather"]
+    if now < weather["until"]:
+        return False
+    while now >= weather["until"]:
+        weather["kind"] = weather["next"]
+        _plan_spell(world, weather, rng)
+    return True
+
+
+def _plan_spell(world: dict, weather: dict, rng: random.Random) -> None:
+    """Set how long the current weather lasts and what follows. Rolls that keep the
+    same weather lengthen the spell, so `until` is when it really changes."""
+    for _ in range(3):
+        weather["until"] += rng.uniform(4, 8) * HOUR / speed(world)
+        weather["next"] = _roll_weather(world, weather["until"], rng, weather["kind"])
+        if weather["next"] != weather["kind"]:
+            return
+    # Three spells of the same is long enough: something else comes next.
+    weights = SEASON_WEATHER[season(world, weather["until"])["index"]]
+    weather["next"] = _pick({kind: w for kind, w in weights.items() if kind != weather["kind"]}, rng)
+
+
 def _modifier_sources(world: dict) -> list[dict]:
     city = world["city"]
     sources = [WEATHER[city["weather"]["kind"]]] + city["effects"]
@@ -2437,11 +2462,7 @@ def hire_mercenaries(world: dict, player: dict, now: float) -> str | None:
 def _happenings_hour(world: dict, now: float, rng: random.Random) -> None:
     """Weather, firewood, thieves and expiries, once per game hour."""
     city = world["city"]
-    weather = city["weather"]
-    if now >= weather["until"]:
-        weather["kind"] = weather["next"]
-        weather["until"] = now + rng.uniform(4, 8) * HOUR / speed(world)
-        weather["next"] = _roll_weather(world, weather["until"], rng, weather["kind"])
+    advance_weather(world, now, rng)
     city["effects"] = [e for e in city["effects"] if e["until"] > now]
     for problem in list(city["problems"]):
         if problem.get("until") and problem["until"] <= now:

static/app.js

@@ -681,15 +681,14 @@ function siteBanner() {
 
 // "Rain: farming 10% faster. Clear skies in 3h 20m."
 function weatherTip(w) {
-  const next = w.next === w.kind ? `Staying ${w.name.toLowerCase()}` : w.next_name;
-  return `${w.name}: ${w.text.charAt(0).toLowerCase()}${w.text.slice(1)}. ${next} in ${dur(w.until - serverNow())}.`;
+  return `${w.name}: ${w.text.charAt(0).toLowerCase()}${w.text.slice(1)}. ${w.next_name} in ${dur(w.until - serverNow())}.`;
 }
 
 function weatherCard() {
   const h = S.happenings, w = h.weather;
   return `<div class="stat" title="${esc(`${weatherTip(w)} Weather changes every few hours; each season lasts a week.`)}"><div class="k">${h.season.icon} ${h.season.name}, day ${h.season.day}</div>
     <div class="v">${w.icon} <small>${esc(w.name)}</small></div>
-    <div class="note">${w.next === w.kind ? `Staying ${esc(w.name.toLowerCase())}` : `${w.next_icon} ${esc(w.next_name)}`} in ${countdown(w.until)}</div></div>`;
+    <div class="note">${w.next_icon} ${esc(w.next_name)} in ${countdown(w.until)}</div></div>`;
 }
 
 // Everything going on in the city right now, and what anyone can do about it.

tests/test_game.py

@@ -302,6 +302,7 @@ class CityTest(unittest.TestCase):
         world = world_with()
         city = world["city"]
         city["stockpile"] = {"bread": 5}
+        world["next_fortune_at"] = None  # no lucky wagon of bread
         game.tick(world, T0 + 4 * game.DAY, random.Random(1))
         self.assertTrue(city["starving"])
         self.assertNotIn("bread", city["stockpile"])
@@ -953,6 +954,18 @@ class HappeningsTest(unittest.TestCase):
         self.assertEqual(game.season(self.world, T0 + 8 * game.DAY)["name"], "Summer")
         self.assertEqual(game.season(self.world, T0 + 22 * game.DAY)["name"], "Winter")
 
+    def test_weather_changes_on_time_and_always_to_something_new(self):
+        weather = self.city["weather"]
+        weather.update(kind="rain", next="clear", until=T0 + 10 * 60)
+        self.city["last_tick"] = T0
+        game.tick(self.world, T0 + 11 * 60, self.rng)  # well inside the hour
+        self.assertEqual(weather["kind"], "clear")
+        for _ in range(50):
+            spell = weather["until"]
+            game.tick(self.world, spell, self.rng)
+            self.assertNotEqual(weather["next"], weather["kind"])
+            self.assertGreater(weather["until"], spell)
+
     def test_days_count_midnights_not_24_hour_stretches(self):
         from datetime import datetime
         late = datetime(2026, 10, 18, 23, 0).timestamp()