Update default category

src/streamlit_app.py

@@ -240,7 +240,8 @@ for key, default in {
     "click_nonce": 0,
     "last_clicked_processed": -1,
     "auto_selected_ids": set(),
-    "image_view": "Original",          # NEW: "Original" | "Modified"
+    "image_view": "Original",      # current radio selection
+    "last_image_view": "Original", # previous radio selection    
 }.items():
     if key not in st.session_state:
         st.session_state[key] = default
@@ -399,6 +400,13 @@ if st.session_state.challenge_images_original:
     st.session_state.image_view = st.radio(
         "Image set", options, horizontal=True, index=0 if st.session_state.image_view not in options else options.index(st.session_state.image_view)
     )
+    # If user switches Original ↔ Modified, treat as "new puzzle view"
+    prev_view = st.session_state.get("last_image_view", "Original")
+    if st.session_state.image_view != prev_view:
+        st.session_state.last_image_view = st.session_state.image_view
+        st.session_state.tile_selected = set()
+        st.session_state.auto_selected_ids = set()
+        st.session_state.click_nonce = 0    
 
     images_to_show = (st.session_state.challenge_images_modified
                       if st.session_state.image_view == "Modified" and st.session_state.challenge_images_modified