Update app.py

app.py

@@ -23,7 +23,7 @@ body::before {
     background-image: url('https://stsci-opo.org/STScI-01J5E849R5W27ZZ2C3QAE9ET75.png');
     background-size: cover;
     background-repeat: no-repeat;
-    opacity: 0.65;             /* Faint background image */
+    opacity: 0.35;             /* Faint background image */
     background-position: center;
     z-index: -1;    /* Keep the background behind text */
 }