Add a gradient mask to reduce centerpiece noise

static/assets/css/index.css

@@ -62,6 +62,12 @@ img.centerpiece {
     animation-timing-function: linear;
     animation-duration: 30s;
     animation-iteration-count: infinite;
+    mask-image: linear-gradient(90deg,
+        light-dark(#222, #000) 0%,
+        light-dark(#888, #444) 50%,
+        #fff 100%
+    );
+    mask-mode: luminance;
 }
 
 img.two { animation-delay: -6s; }
@@ -116,7 +122,8 @@ img.five { animation-delay: -30s; }
         blur(0)
         saturate(1.2)
         contrast(2)
-        ;    }
+        ;
+    }
 
     100% {
         transform: rotate3d(0, 1, 0, 360deg);