Use existing shadow value

src/components/organisms/GanttChart.tsx

@@ -253,7 +253,7 @@ const GanttChart = ({
                   minWidth: length,
                   width: 'inherit',
                   zIndex: 25,
-                  boxShadow: '0 4px 8px rgba(0, 0, 0, 0.2)',
+                  boxShadow: 'default',
                   transition: 'box-shadow 200ms ease-in-out',
                 },
               }}

src/components/organisms/RootNavigator.tsx

@@ -10,7 +10,7 @@ const RootNavigator = () => {
       sx={{
         alignItems: 'center',
         position: 'sticky',
-        backgroundColor: 'rgba(255,255,255,0.9)',
+        backgroundColor: 'transparent',
         top: 0,
         zIndex: 100,
       }}