diff --git a/docs/code_structure.md b/docs/code_structure.md
index b790061..5616e7f 100644
--- a/docs/code_structure.md
+++ b/docs/code_structure.md
@@ -8,7 +8,7 @@
   -- can return applicable list based on item type
 
 [class] Environment
-    [dict] Environment Configuration
+    [set] Environment Configuration
 
 [class] Build
     [ref] Tree
@@ -16,16 +16,17 @@
 
 [class] Tree
     [str] version
-    [dict] All Nodes (addressable by Node ID)
-    [dict] Selected Nodes (addressable by Node ID)
+    [set] All Nodes (addressable by Node ID)
+    [set] Allocated Nodes (addressable by Node ID)
 
 [class] Player
     [enum] Class Selection
     [enum] Ascendancy Selection
-    [dict] Stats (e.g. Str/Dex/Int, Hit/Crit, Life/Mana, Block/Spell Block/Evade/Dodge, etc.)
-    [dict] Item Slots
+    [set] Stats (e.g. Str/Dex/Int, Hit/Crit, Life/Mana, Block/Spell Block/Evade/Dodge, etc.)
+    [list] Skills
+    [set] Item Sets
         [per slot ref] Item
-    [optional list] Minions
+    [optional set] Minions
 
 [class] Item
     [dict] Attribute requirements
@@ -43,24 +44,26 @@
 
 [class] Minion
     [ref] Player
-    [dict] Stats
+    [set] Stats
     [ref list] Items
     [ref list] Skills
     [int] Quantity
 
 [class] EnemyModel (e.g. Shaper, Maven)
-    [dict] Stats (e.g. Str/Dex/Int, Hit/Crit, Life/Mana, Block/Spell Block/Evade/Dodge, etc.)
+    [str] Name
+    [set] Stats (e.g. Str/Dex/Int, Hit/Crit, Life/Mana, Block/Spell Block/Evade/Dodge, etc.)
 
 [class] Simulator
     [ref] Environment(s)
     [ref list] Build(s)
     [ref] Enemy Model(s)
 
-[class] Analytics Module
+[module] Analytics Module
     [func] Node Comparison
     [func] Item Comparison
     [func] Gem Comparison
+    [func] Minion Comparison
 
-[list] Saved Builds
+[set] Saved Builds
 
 [dict] UI API imports/exports
diff --git a/src/Build.py b/src/Build.py
new file mode 100755
index 0000000..71e07a1
--- /dev/null
+++ b/src/Build.py
@@ -0,0 +1,36 @@
+"""
+Build Class
+
+The build class is the top-level class encompassing all attributes and
+parameters defining a build. It is defined by a specific Tree and Player
+instance at time of evaluation.
+
+The intent is that there is only one Build for a character. There might be
+numerous Passive Trees (at various Player Levels, or various Cluster Jewels)
+associated with a Player.
+"""
+
+import Tree
+import Player
+
+
+class Build:
+    def __init__(self, name: str = "temp") -> None:
+        self.name = name
+        self.tree = Tree.Tree()
+        self.player = Player.Player()
+
+    def __repr__(self) -> str:
+        ret_str = f"[BUILD]: '{self.name}'\n"
+        ret_str += f"{self.tree}"
+        ret_str += f"{self.player}"
+        return ret_str
+
+
+def test() -> None:
+    build = Build()
+    print(build)
+
+
+if __name__ == "__main__":
+    test()
diff --git a/src/Enumerations.py b/src/Enumerations.py
new file mode 100644
index 0000000..9670ec5
--- /dev/null
+++ b/src/Enumerations.py
@@ -0,0 +1,17 @@
+# Enumeration Data for Path of Exile constants
+
+from enum import Enum
+
+
+class PlayerClasses(Enum):
+    SCION = 0
+    MARAUDER = 1
+    RANGER = 2
+    WITCH = 3
+    DUELIST = 4
+    TEMPLAR = 5
+    SHADOW = 6
+
+
+class PlayerAscendancies(Enum):
+    NONE = None
diff --git a/src/Player.py b/src/Player.py
new file mode 100755
index 0000000..b4816b4
--- /dev/null
+++ b/src/Player.py
@@ -0,0 +1,41 @@
+"""
+Player Class
+
+The Player represents an in-game character at a specific point in their
+leveling progress.
+
+A unique Player is defined by: level, class selection, ascendancy selection,
+skill selection, and itemization across the item sets.
+"""
+
+from Enumerations import PlayerClasses, PlayerAscendancies
+
+
+class Player:
+    def __init__(
+        self,
+        player_class: PlayerClasses = PlayerClasses.SCION,
+        ascendancy: PlayerAscendancies = PlayerAscendancies.NONE,
+        level: int = 1,
+    ) -> None:
+        self.player_class = player_class
+        self.ascendancy = ascendancy
+        self.level = level
+        self.stats = set()
+        self.skills = list()
+        self.item_sets = set()
+        self.minions = set()
+
+    def __repr__(self) -> str:
+        ret_str = f"Level {self.level} {self.player_class.name}"
+        ret_str += f" {self.ascendancy.value}\n" if self.ascendancy.value else "\n"
+        return ret_str
+
+
+def test() -> None:
+    player = Player()
+    print(player)
+
+
+if __name__ == "__main__":
+    test()
diff --git a/src/Tree.py b/src/Tree.py
new file mode 100755
index 0000000..8ab8f73
--- /dev/null
+++ b/src/Tree.py
@@ -0,0 +1,33 @@
+"""
+Tree Class
+
+This class represents an instance of the Passive Tree for a given Build.
+Multiple Trees can exist in a single Build (at various progress levels;
+at different Jewel/Cluster itemizations, etc.)
+
+A Tree is tied to a Version of the Tree as released by GGG and thus older Trees
+need to be supported for backwards compatibility reason.
+
+"""
+
+_VERSION_ = "3.17"
+
+
+class Tree:
+    def __init__(self, version: str = _VERSION_) -> None:
+        self.version = version
+        self.tree_nodes = set()
+        self.allocated_nodes = set()
+
+    def __repr__(self) -> str:
+        ret_str = f"[TREE]: version '{self.version}'\n"
+        return ret_str
+
+
+def test() -> None:
+    tree = Tree()
+    print(tree)
+
+
+if __name__ == "__main__":
+    test()
diff --git a/src/__init__.py b/src/__init__.py
new file mode 100644
index 0000000..e69de29