Update app.py

app.py

@@ -374,10 +374,7 @@ body { background: var(--bg) !important; }
 .hero {
   border-radius: 18px;
   padding: 22px 26px;
-  background: linear-gradient(135deg,
-    color-mix(in oklab, var(--primary) 28%, transparent),
-    color-mix(in oklab, var(--secondary) 24%, transparent));
-  border: 1px solid color-mix(in oklab, var(--ink) 12%, transparent);
+  background: #3F51B5;
   box-shadow: 0 12px 36px rgba(0,0,0,.14);
   margin: 8px 0 16px 0;
 }