Update app.py

app.py

@@ -587,6 +587,27 @@ html, body, .gradio-container {
     border-radius: 18px !important;
 }
 
+/* user bubble */
+#chatbot [data-testid="chatbot-message-user"],
+#chatbot .message.user,
+#chatbot .user {
+    background: #d9fdd3 !important;
+    color: #1f2c34 !important;
+    border-radius: 16px !important;
+    border: 1px solid #c7edc1 !important;
+}
+
+/* assistant bubble */
+#chatbot [data-testid="chatbot-message-assistant"],
+#chatbot .message.bot,
+#chatbot .bot,
+#chatbot .assistant {
+    background: #ffffff !important;
+    color: #1f2c34 !important;
+    border-radius: 16px !important;
+    border: 1px solid #e4e7e7 !important;
+}
+
 textarea, input, .wrap textarea {
     border-radius: 18px !important;
     border: 1px solid #d5ddd9 !important;
@@ -650,6 +671,9 @@ def build_header_html() -> str:
 
 def respond(message, history, learning_mode, quiz_questions, show_sources):
     history = history or []
+    message = (message or "").strip()
+    if not message:
+        return history, ""
 
     answer_text, sources = get_answer_and_sources(
         message=message,
@@ -715,8 +739,7 @@ with gr.Blocks(title=APP_TITLE) as demo:
             chatbot = gr.Chatbot(
                 height=500,
                 elem_id="chatbot",
-                show_label=False,
-                type="messages"
+                show_label=False
             )
 
             msg = gr.Textbox(