Use less saturated colors for metro lines

Author: yanfengliu

GAME_RULES.md

@@ -50,7 +50,7 @@ This document summarizes the game rules currently implemented in code.
   - Unlock the 4th station at 10 travels.
   - Then each next station requires +20 more travels than the previous unlock
     (5th at 40, 6th at 90, 7th at 160, ...), up to 20 stations.
-- Line colors are randomized at runtime each run.
+- Line colors are randomized at runtime each run, using a less saturated palette for softer visuals.
 
 ## Passenger Routing and Transfers
 

PROGRESS.md

@@ -75,3 +75,4 @@
 - Updated `GAME_RULES.md` to document the station snap-blip behavior during line creation.
 - Added bottom-left simulation speed controls (`Pause`, `1x`, `2x`, `4x`) with clickable UI buttons wired to pause and speed state.
 - Switched speed-control button labels to iconography: pause bars, single play, double play, and four-play symbols.
+- Changed runtime-randomized metro line colors to a less saturated palette for softer visuals.

src/mediator.py

@@ -129,9 +129,9 @@ def generate_distinct_path_colors(self, path_count: int) -> Dict[Color, bool]:
             selected_hues.append(pick_distinct_hue(selected_hues, candidate_hues))
         path_colors: Dict[Color, bool] = {}
         for hue in selected_hues:
-            path_colors[hue_to_rgb(hue)] = False
+            path_colors[hue_to_rgb(hue, saturation=0.6, value=0.9)] = False
         while len(path_colors) < path_count:
-            path_colors[hue_to_rgb(random.random())] = False
+            path_colors[hue_to_rgb(random.random(), saturation=0.6, value=0.9)] = False
         return path_colors
 
     def get_path_purchase_prices(self) -> List[int]:

src/utils.py

@@ -33,8 +33,8 @@ def get_random_color() -> Color:
     return hue_to_rgb(np.random.rand())
 
 
-def hue_to_rgb(hue: float) -> Color:
-    return tuple(255 * np.asarray(colorsys.hsv_to_rgb(hue, 1.0, 1.0)))
+def hue_to_rgb(hue: float, saturation: float = 1.0, value: float = 1.0) -> Color:
+    return tuple(255 * np.asarray(colorsys.hsv_to_rgb(hue, saturation, value)))
 
 
 def hue_circular_distance(hue_a: float, hue_b: float) -> float:

test/test_mediator.py

@@ -102,7 +102,7 @@ def test_generate_distinct_path_colors_handles_non_positive_count(self):
     def test_generate_distinct_path_colors_backfills_color_collisions(self):
         calls = {"count": 0}
 
-        def fake_hue_to_rgb(_hue):
+        def fake_hue_to_rgb(_hue, saturation=1.0, value=1.0):
             calls["count"] += 1
             if calls["count"] <= self.mediator.num_paths:
                 return (0, 0, 0)