diff --git a/hamstertools/app.py b/hamstertools/app.py
index 3836cc7..d595795 100644
--- a/hamstertools/app.py
+++ b/hamstertools/app.py
@@ -1,16 +1,15 @@
 from textual.app import App, ComposeResult
-from textual.widgets import Header, Footer, DataTable
+from textual.widgets import Header, Footer, DataTable, Placeholder
 from textual.coordinate import Coordinate
+from textual.screen import Screen
 
 
-class HamsterToolsApp(App):
-    """A Textual app to manage stopwatches."""
-
+class ActivitiesScreen(Screen):
     BINDINGS = [
         ("q", "quit", "Quit"),
         ("s", "sort", "Sort"),
         ("r", "refresh", "Refresh"),
-        ("d", "delete_activity", "Delete activity"),
+        ("d", "delete", "Delete activity"),
     ]
 
     def __init__(self, db_cursor, db_connection):
@@ -22,28 +21,28 @@ class HamsterToolsApp(App):
         self.table.clear()
 
         sql = '''
-        SELECT
-            categories.id AS category_id,
-            COALESCE(categories.name, '') AS category_name,
-            activities.id AS activity_id,
-            activities.name AS activity_name,
-            COALESCE(facts_count, 0) AS total_facts
-        FROM
+        select
+            categories.id as category_id,
+            coalesce(categories.name, '') as category_name,
+            activities.id as activity_id,
+            activities.name as activity_name,
+            coalesce(facts_count, 0) as total_facts
+        from
             activities
-        LEFT JOIN
+        left join
             categories
-        ON
+        on
             activities.category_id = categories.id
-        LEFT JOIN (
-            SELECT
+        left join (
+            select
                 activity_id,
-                COUNT(*) AS facts_count
-            FROM
+                count(*) as facts_count
+            from
                 facts
-            GROUP BY
+            group by
                 activity_id
-        ) AS facts_count_subquery
-        ON
+        ) as facts_count_subquery
+        on
             activities.id = facts_count_subquery.activity_id;
             '''
 
@@ -54,7 +53,7 @@ class HamsterToolsApp(App):
         self.table.sort(self.columns[1], self.columns[3])
 
     def compose(self) -> ComposeResult:
-        """Create child widgets for the app."""
+        """create child widgets for the app."""
         yield Header()
         yield DataTable()
         yield Footer()
@@ -62,36 +61,152 @@ class HamsterToolsApp(App):
     def on_mount(self) -> None:
         self.table = self.query_one(DataTable)
         self.table.cursor_type = "row"
-        self.columns = self.table.add_columns("category id","category","activity ID","activity","entries")
+        self.columns = self.table.add_columns("category id","category","activity id","activity","entries")
         self._refresh()
 
-    def action_quit(self) -> None:
-        self.exit()
-
     def action_refresh(self) -> None:
         self._refresh()
 
     def action_sort(self) -> None:
         self.table.cursor_type = "column"
 
-    def action_delete_activity(self) -> None:
-         # Get the keys for the row and column under the cursor.
+    def action_delete(self) -> None:
+         # get the keys for the row and column under the cursor.
         row_key, _ = self.table.coordinate_to_cell_key(self.table.cursor_coordinate)
 
         activity_id = self.table.get_cell_at(
             Coordinate(self.table.cursor_coordinate.row, 2),
         )
 
-        sql = 'DELETE FROM activities WHERE id = ?'
+        sql = 'delete from activities where id = ?'
         print(Coordinate(2, self.table.cursor_coordinate.row),)
         print(activity_id)
 
         self.db_cursor.execute(sql, (activity_id,))
         self.db_connection.commit()
 
-        # Supply the row key to `remove_row` to delete the row.
+        # supply the row key to `remove_row` to delete the row.
         self.table.remove_row(row_key)
 
     def on_data_table_column_selected(self, event):
         event.data_table.sort(event.column_key)
         event.data_table.cursor_type = "row"
+
+
+class CategoriesScreen(Screen):
+    BINDINGS = [
+        ("s", "sort", "Sort"),
+        ("r", "refresh", "Refresh"),
+        ("d", "delete", "Delete category"),
+    ]
+
+    def __init__(self, db_cursor, db_connection):
+        self.db_cursor = db_cursor
+        self.db_connection = db_connection
+        super().__init__()
+
+    def _refresh(self):
+        self.table.clear()
+
+        sql = '''
+        select
+            categories.id as category_id,
+            coalesce(categories.name, '') as category_name,
+            coalesce(activities_count, 0) as total_activities
+        from
+            categories
+        left join (
+            select
+                category_id,
+                count(*) as activities_count
+            from
+                activities
+            group by
+                category_id
+        ) as activities_count_subquery
+        on
+            categories.id = activities_count_subquery.category_id;
+            '''
+
+        results = self.db_cursor.execute(sql)
+        # results = [[cell or "" for cell in row] for row in self.db_cursor.fetchall()]
+
+        self.table.add_rows(results)
+        self.table.sort(self.columns[1])
+
+    def compose(self) -> ComposeResult:
+        """create child widgets for the app."""
+        yield Header()
+        yield DataTable()
+        yield Footer()
+
+    def on_mount(self) -> None:
+        self.table = self.query_one(DataTable)
+        self.table.cursor_type = "row"
+        self.columns = self.table.add_columns("category id","category","activities")
+        self._refresh()
+
+    def action_refresh(self) -> None:
+        self._refresh()
+
+    def action_sort(self) -> None:
+        self.table.cursor_type = "column"
+
+    def action_delete(self) -> None:
+        # get the keys for the row and column under the cursor.
+        row_key, _ = self.table.coordinate_to_cell_key(self.table.cursor_coordinate)
+
+        category_id = self.table.get_cell_at(
+            Coordinate(self.table.cursor_coordinate.row, 0),
+        )
+
+        sql = 'delete from categories where id = ?'
+        print(Coordinate(2, self.table.cursor_coordinate.row),)
+        print(category_id)
+
+        self.db_cursor.execute(sql, (category_id,))
+        self.db_connection.commit()
+
+        # supply the row key to `remove_row` to delete the row.
+        self.table.remove_row(row_key)
+
+    def on_data_table_column_selected(self, event):
+        event.data_table.sort(event.column_key)
+        event.data_table.cursor_type = "row"
+
+# class KimaiScreen(Screen):
+#     def compose(self) -> ComposeResult:
+#         yield Placeholder("Help Screen")
+#         yield Footer()
+#
+#     def __init__(self, db_cursor, db_connection):
+#         self.db_cursor = db_cursor
+#         self.db_connection = db_connection
+#         super().__init__()
+
+
+class HamsterToolsApp(App):
+    BINDINGS = [
+        ("a", "switch_mode('activities')", "Activities"),
+        ("c", "switch_mode('categories')", "Categories"),
+        # ("k", "switch_mode('kimai')", "Kimai"),
+        ("q", "quit", "Quit"),
+    ]
+    def __init__(self, db_cursor, db_connection):
+        self.db_cursor = db_cursor
+        self.db_connection = db_connection
+
+        self.MODES = {
+            "categories": CategoriesScreen(db_cursor, db_connection),
+            "activities": ActivitiesScreen(db_cursor, db_connection),
+            # "kimai": KimaiScreen,
+        }
+
+        super().__init__()
+
+    def on_mount(self) -> None:
+        self.switch_mode("activities")
+
+    def action_quit(self) -> None:
+        self.exit()
+