Update index.html

index.html

@@ -517,7 +517,8 @@
   }
 
   function adjustBrightness(color, percent) {
-    const num = parseInt(color.replace('#', ''), amt = Math.round(2.55 * percent);
+    const num = parseInt(color.replace('#', ''), 16);
+    const amt = Math.round(2.55 * percent);
     const R = (num >> 16) + amt;
     const G = (num >> 8 & 0x00FF) + amt;
     const B = (num & 0x0000FF) + amt;