diff --git a/dcs/__main__.py b/dcs/__main__.py
new file mode 100644
index 0000000..194ffbd
--- /dev/null
+++ b/dcs/__main__.py
@@ -0,0 +1,11 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from .main import main
+
+
+if __name__ == '__main__':
+    main()
diff --git a/dcs/frames/__init__.py b/dcs/frames/__init__.py
new file mode 100644
index 0000000..4e5dd51
--- /dev/null
+++ b/dcs/frames/__init__.py
@@ -0,0 +1,21 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from typing import List, Type
+from . import base
+
+
+def get_windows() -> List[Type[base.Window]]:
+    return [
+    ]
+
+
+def get_groups() -> List[Type[base.Group]]:
+    return base.get_groups(get_windows())
+
+
+def get_win_of_group(grp: Type[base.Group]) -> List[Type[base.Window]]:
+    return base.get_win_of_group(get_windows(), grp)
diff --git a/dcs/frames/base.py b/dcs/frames/base.py
new file mode 100644
index 0000000..bc939d8
--- /dev/null
+++ b/dcs/frames/base.py
@@ -0,0 +1,61 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import logging
+from tkinter import ttk, Tk, Toplevel, BOTH
+from typing import Type, List
+
+
+class Group:
+    NAME: str
+
+
+class BaseFrame(ttk.Frame):
+    pass
+
+
+class Window:
+    GROUP: Type[Group]
+    TITLE: str
+    FRAME: Type[BaseFrame]
+
+    @classmethod
+    def make_title(cls) -> str:
+        return f'{cls.GROUP.NAME} - {cls.TITLE}'
+
+    @classmethod
+    def make_frame(cls, root) -> ttk.Frame:
+        frm = cls.FRAME(root)
+        frm.pack(expand=True, fill=BOTH)
+        return frm
+
+    @classmethod
+    def make_window(cls, root) -> Toplevel:
+        win = Toplevel(root)
+        win.title(cls.make_title())
+        cls.make_frame(win)
+        return win
+
+    @classmethod
+    def main(cls):
+        logging.basicConfig(level=logging.INFO)
+
+        root = Tk()
+        root.title(cls.make_title())
+        cls.make_frame(root)
+        root.mainloop()
+
+
+def get_groups(win_cls: List[Type[Window]]) -> List[Type[Group]]:
+    grp_cls: List[Type[Group]] = []
+    for win in win_cls:
+        if win.GROUP not in grp_cls:
+            grp_cls.append(win.GROUP)
+    return list(sorted(grp_cls, key=lambda grp: grp.NAME))
+
+
+def get_win_of_group(win_cls: List[Type[Window]], grp: Type[Group]) -> List[Type[Window]]:
+    return list(filter(lambda win: win.GROUP == grp, win_cls))
diff --git a/dcs/frames/groups.py b/dcs/frames/groups.py
new file mode 100644
index 0000000..4ad16f4
--- /dev/null
+++ b/dcs/frames/groups.py
@@ -0,0 +1,11 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from .base import Group
+
+
+class Ch02Group(Group):
+    NAME = 'Chapter 02'
diff --git a/dcs/main.py b/dcs/main.py
new file mode 100644
index 0000000..a955249
--- /dev/null
+++ b/dcs/main.py
@@ -0,0 +1,67 @@
+#  SPDX-License-Identifier: MPL-2.0
+#    Copyright (c) 2022 Philipp Le <philipp@philipple.de>.
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+from dcs.frames import get_groups, get_win_of_group
+from dcs.frames.base import Group, Window
+import logging
+from tkinter import ttk, Tk, BOTTOM, BOTH
+from typing import Type, Dict, Any
+import webbrowser
+
+
+class MainWindow(ttk.Frame):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        self.wdg_treeview = ttk.Treeview(self)
+        self.wdg_treeview.pack(expand=True, fill=BOTH)
+        self.wdg_treeview.bind('<Double-Button-1>', self._on_double_click)
+
+        self.group_ids: Dict[Type[Group], Any] = {}
+        self.win_ids: Dict[Type[Window], Any] = {}
+        for grp in get_groups():
+            self.group_ids[grp] = self.wdg_treeview.insert('', 'end', None, text=grp.NAME)
+            for win in get_win_of_group(grp):
+                self.win_ids[win] = self.wdg_treeview.insert(self.group_ids[grp], 'end', None, text=win.TITLE)
+
+        self.frm_copyright = ttk.Frame(self, height=35)
+        self.frm_copyright.pack(side=BOTTOM, expand=False)
+        ttk.Label(self.frm_copyright, text='Copyright (c) 2022 Philipp Le').pack()
+        self.wdg_license = ttk.Button(self.frm_copyright, text='Mozilla Public License v2.0',
+                                      command=self._view_license)
+        self.wdg_license.pack()
+
+    def find_win(self, iid) -> Type[Window]:
+        for win, win_iid in self.win_ids.items():
+            if win_iid == iid:
+                return win
+        raise KeyError
+
+    def _on_double_click(self, event):
+        item_id = event.widget.focus()
+        try:
+            win = self.find_win(item_id)
+            win.make_window(self)
+        except KeyError:
+            pass
+
+    def _view_license(self):
+        webbrowser.open('https://mozilla.org/MPL/2.0/', new=1)
+
+
+def main():
+    logging.basicConfig(level=logging.INFO)
+
+    root = Tk()
+    root.title('Digital Communication Systemes - Interactive')
+    root.geometry('800x600')
+    win = MainWindow(root)
+    win.pack(expand=True, fill=BOTH)
+    root.mainloop()
+
+
+if __name__ == '__main__':
+    main()