Update app.py

app.py

@@ -456,3 +456,38 @@ Follow these conventions to keep your code clean and readable:
 ```python
 if __name__ == "__main__":
     main()
+
+with gr.Tabs():
+    # Main lesson tabs
+    for lesson in lessons:
+        with gr.Tab(lesson["title"]):
+            gr.Markdown(lesson["description"])
+
+            code = gr.Code(
+                value=lesson["starter_code"],
+                language="python",
+                label="✏️ Edit and run your Python code here",
+                interactive=True,
+            )
+
+            with gr.Row():
+                run_button = gr.Button("▶️ Run code", variant="primary")
+                clear_button = gr.Button("🧹 Clear output")
+
+            output = gr.Textbox(
+                label="📤 Output (stdout and errors)",
+                lines=14,
+                show_copy_button=True,
+            )
+
+            # Bind buttons
+            run_button.click(run_python, inputs=code, outputs=output)
+            clear_button.click(lambda: "", outputs=output)
+
+    # References / Appendices tab
+    with gr.Tab("References & Appendices"):
+        gr.Markdown(appendix_markdown)
+
+gr.Markdown(
+    """
+