Give the event banners a top-down night gradient so they read as lit cloth

CHANGELOG.md

@@ -8,6 +8,7 @@ Semantic Versioning.
 
 ### Fixed
 
+- The red event banners are lit from the top down at night instead of reading as flat red cards.
 - Street lamps now throw a warm pool on the pavement instead of dimly washing the whole walkway.
 - The flashlight actually lights what it points at. It was tuned to a beam so weak it changed the
   frame by less than one 255th of a level; it now throws a visible pool on the door and the pavement