diff --git a/screens/classic_mode.py b/screens/classic_mode.py
index 505e89d..e7e7e30 100644
--- a/screens/classic_mode.py
+++ b/screens/classic_mode.py
@@ -6,6 +6,10 @@
 ### Imports ###
 ###############
 
+### Python imports ###
+
+from functools import partial
+
 ### Kivy imports ###
 
 from kivy.properties import (
@@ -82,6 +86,11 @@ def fill_scrollview(self):
                 nb_levels=nb_levels,
                 nb_completed_levels=nb_completed_levels,
                 nb_stars=0,
-                font_ratio=self.font_ratio)
+                font_ratio=self.font_ratio,
+                release_function=partial(self.open_levels_screen, act))
             self.ACT_BUTTON_DICT[act] = current_act_button
             scrollview_layout.add_widget(self.ACT_BUTTON_DICT[act])
+
+    def open_levels_screen(self, act_id):
+        self.manager.get_screen("levels").current_act_id = act_id
+        self.manager.current = "levels"
diff --git a/screens/custom_widgets/__init__.py b/screens/custom_widgets/__init__.py
index 259a5a4..c0a0a9f 100644
--- a/screens/custom_widgets/__init__.py
+++ b/screens/custom_widgets/__init__.py
@@ -20,3 +20,4 @@
 from screens.custom_widgets.circle_icon_button import CircleIconButton
 from screens.custom_widgets.round_button import RoundButton
 from screens.custom_widgets.booster_layout import BoosterLayout
+from screens.custom_widgets.levels_branchs import (LevelButton)
diff --git a/screens/custom_widgets/levels_branchs.kv b/screens/custom_widgets/levels_branchs.kv
new file mode 100644
index 0000000..ef903f1
--- /dev/null
+++ b/screens/custom_widgets/levels_branchs.kv
@@ -0,0 +1,34 @@
+#:kivy 2.2.1
+#:import PATH_TEXT_FONT tools.path.PATH_TEXT_FONT
+#:import LEVEL_ID_FONT_SIZE tools.constants.LEVEL_ID_FONT_SIZE
+
+<LevelButton>:
+
+    Widget:
+        opacity: 0.8
+        size: root.size
+        pos: (0,0)
+        canvas.before:
+            Color:
+                rgba: self.parent.primary_color
+            RoundedRectangle:
+                pos:(0,0)
+                size:self.size
+                radius:[15,]
+    
+    Label:
+        id: level_label
+        text: root.level_label_text
+        pos_hint: {"center_x":0.5, "center_y":0.65}
+        font_size: LEVEL_ID_FONT_SIZE * root.font_ratio
+        font_name: PATH_TEXT_FONT
+
+
+    # Stars
+    ThreeStars:
+        id: three_stars
+        pos_hint: {"center_x":0.5, "center_y":0.25}
+        size_hint: (0.8,0.45)
+        nb_stars: root.nb_stars
+
+# <LevelLeftBranch>:
diff --git a/screens/custom_widgets/levels_branchs.py b/screens/custom_widgets/levels_branchs.py
new file mode 100644
index 0000000..bee494e
--- /dev/null
+++ b/screens/custom_widgets/levels_branchs.py
@@ -0,0 +1,80 @@
+"""
+Module to create the levels tree for the levels screen.
+"""
+
+###############
+### Imports ###
+###############
+
+### Kivy imports ###
+
+from kivy.uix.relativelayout import RelativeLayout
+from kivy.uix.behaviors import ButtonBehavior
+from kivy.properties import (
+    NumericProperty,
+    BooleanProperty,
+    ColorProperty,
+    StringProperty
+)
+
+### Local imports ###
+from tools.path import (
+    PATH_TEXT_FONT
+)
+from tools.constants import (
+    GAMEPLAY_DICT,
+    OPACITY_ON_BUTTON_PRESS
+)
+
+
+###############
+### Classes ###
+###############
+
+class LevelButton(ButtonBehavior, RelativeLayout):
+
+    nb_stars = NumericProperty()
+    font_ratio = NumericProperty(1)
+    level_label_text = StringProperty()
+    primary_color = ColorProperty((0.5, 0.5, 0.5, 1))
+    secondary_color = ColorProperty((0.2, 0.2, 0.2, 1))
+    is_unlocked = BooleanProperty(False)
+    disable_button = BooleanProperty(False)
+
+    def __init__(
+            self,
+            level_id=0,
+            release_function=lambda: 1 + 1,
+            is_unlocked=False,
+            **kw):
+        super().__init__(**kw)
+        self.release_function = release_function
+        self.always_release = True
+        self.is_unlocked = is_unlocked
+        self.level_id = level_id
+        self.level_label_text = str(level_id)
+
+    def on_press(self):
+        if not self.disable_button:
+            self.opacity = OPACITY_ON_BUTTON_PRESS
+
+    def on_release(self):
+        if not self.disable_button:
+            self.release_function()
+            self.opacity = 1
+
+
+class LevelBranch(RelativeLayout):
+    def __init__(
+            self,
+            act_id,
+            branch_id,
+            **kw):
+        super().__init__(**kw)
+        self.act_id = act_id
+        self.branch_id = branch_id
+
+    def build_layout(self):
+        # Find the number of levels contained in the branch, cannot be greater than 5
+        nb_levels = ...
+        self.local_nb_levels = ...
diff --git a/screens/custom_widgets/theme_layout.py b/screens/custom_widgets/theme_layout.py
index ae186a4..c2211c1 100644
--- a/screens/custom_widgets/theme_layout.py
+++ b/screens/custom_widgets/theme_layout.py
@@ -1,5 +1,5 @@
 """
-Module to create the act button.
+Module to create the theme selection layout.
 """
 
 ###############
@@ -35,7 +35,7 @@
 
 class ThemeLayout(Image):
     """
-    A layout to display the customization to buy.
+    A layout to select the image or the colors of a theme.
     """
 
     theme_title = StringProperty()
@@ -77,6 +77,9 @@ def __init__(
         self.font_size = font_size
 
     def update_variables(self):
+        """
+        Update the variables to indicate if a component is selected or unlocked.
+        """
         if self.theme_key in USER_DATA.unlocked_themes:
             self.has_bought_image = USER_DATA.unlocked_themes[self.theme_key]["image"]
             self.has_bought_colors = USER_DATA.unlocked_themes[self.theme_key]["colors"]
@@ -102,6 +105,9 @@ def update_display(self):
         self.ids["buy_colors_button"].update_display()
 
     def click_image(self):
+        """
+        Function to select the image of the theme.
+        """
         if not self.has_bought_image:
             bought_sucessfully = USER_DATA.buy_item(
                 self.theme_key, "image", self.image_price)
@@ -116,6 +122,9 @@ def click_image(self):
                 "themes").update_theme_layouts_display()
 
     def click_colors(self):
+        """
+        Function to select the colors of the theme.
+        """
         if not self.has_bought_colors:
             bought_sucessfully = USER_DATA.buy_item(
                 self.theme_key, "colors", self.colors_price)
diff --git a/screens/levels.kv b/screens/levels.kv
index 2ce154d..21253b6 100644
--- a/screens/levels.kv
+++ b/screens/levels.kv
@@ -11,7 +11,7 @@
 
 <LevelsScreen>:
     Label:
-        text: "Linconym"
+        text: "Classic Mode"
         font_name: PATH_TITLE_FONT
         font_size: TITLE_FONT_SIZE * root.font_ratio
         pos_hint: {"center_x":0.5, "center_y":0.9}
@@ -23,3 +23,11 @@
         size_hint: (1, BOTTOM_BAR_HEIGHT)
         pos_hint: {"bottom":0,"left":0}
         selected: "none"
+
+    LevelButton:
+        pos_hint: {"center_x":0.5, "center_y":0.5}
+        size_hint: (0.15, None)
+        height: self.width*0.8
+        font_ratio: root.font_ratio
+
+
diff --git a/screens/levels.py b/screens/levels.py
index ddb8352..2348148 100644
--- a/screens/levels.py
+++ b/screens/levels.py
@@ -37,6 +37,7 @@ def __init__(self, **kwargs) -> None:
             back_image_path=PATH_BACKGROUNDS +
             THEMES_DICT[current_theme_image]["image"],
             **kwargs)
+        self.current_act_id = ""
 
     def on_enter(self, *args):
         return super().on_enter(*args)
diff --git a/screens/themes.py b/screens/themes.py
index ed426d4..56d65e0 100644
--- a/screens/themes.py
+++ b/screens/themes.py
@@ -92,13 +92,14 @@ def update_theme_layouts_display(self):
         current_theme_colors = USER_DATA.settings["current_theme_colors"]
         self.primary_color = THEMES_DICT[current_theme_colors]["primary"]
 
-        # if self.back_image_path != PATH_BACKGROUNDS + new_image:
-        # Change the background image smoothly for this screen
-        self.change_background(new_image)
-
-        # Change the background image for all screens except this one
-        self.manager.change_all_background_images(
-            PATH_BACKGROUNDS + new_image)
+        if (self.back_image_path != PATH_BACKGROUNDS + new_image and self.opacity_state == "main") \
+                or (self.second_back_image_path != PATH_BACKGROUNDS + new_image and self.opacity_state == "second"):
+            # Change the background image smoothly for this screen
+            self.change_background(new_image)
+
+            # Change the background image for all screens except this one
+            self.manager.change_all_background_images(
+                PATH_BACKGROUNDS + new_image)
 
     def change_background(self, new_image: str):
         """
diff --git a/tools/constants.py b/tools/constants.py
index deaa6d9..307a17a 100644
--- a/tools/constants.py
+++ b/tools/constants.py
@@ -198,6 +198,7 @@ def __init__(self) -> None:
 EXPERIENCE_FONT_SIZE = 15
 POS_HINT_BACK_ARROW = {"x": 0.02, "top": 0.99}
 RATE_CHANGE_OPACITY = 0.05
+LEVEL_ID_FONT_SIZE = 22
 
 ### Musics ###