weather: add lightning flashes during storms

config.js

@@ -136,9 +136,17 @@ window.CONFIG = {
             intensity: 1.0,
             maxAlpha: 0.45,
             speed: 0.35           // slow drifting flakes
+        },
+        lightning: {
+            enabled: true,
+            gain: 1.2,            // brightness of one flash
+            minDelayS: 8,         // minimum delay between storm flashes
+            maxDelayS: 45,        // maximum delay between storm flashes
+            doubleFlash: true     // some flashes flicker twice
         }
         // weatherEffects: { enabled: false }
         // weatherEffects: { rain: { maxAlpha: 0.55, speed: 1.4 }, snow: { enabled: false } }
+        // weatherEffects: { lightning: { gain: 2.0, minDelayS: 3, maxDelayS: 12 } }
     },
 
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