Update src/app.py

src/app.py

@@ -499,8 +499,7 @@ with tab3:
             # =====================================================
             st.markdown("#### 3️⃣ 2D Density Heatmap")
             st.caption("Binned heatmap of editing values by position — similar to a FACS density plot.")
-
-            y_bins = st.slider("Vertical bins:", min_value=20, max_value=150, value=60, key="heatmap_ybins")
+            y_bins = st.number_input("Vertical bins:", min_value=20, max_value=150, value=60, key="heatmap_ybins")
 
             positions_unique = sorted(melted["Position_idx"].unique())
             n_positions = len(positions_unique)