diff --git a/lindenmayer/__main__.py b/lindenmayer/__main__.py
index 70c01bc..eaf9e07 100644
--- a/lindenmayer/__main__.py
+++ b/lindenmayer/__main__.py
@@ -1,17 +1,25 @@
 import drawer
 import turtle
+import lSystems
+import inputHelper
 turtle.tracer(0, 0)
 turtleObject = turtle.Turtle()
 turtleObject.hideturtle()
-simulatedDraw = drawer.DrawerSimulation({"F": "F[+F]F[-F]F"}, 25.7, 1, turtle.Vec2D(0, 0), 90.0, turtleObject)
-simulatedDraw.draw("F", 5)
-xDistance = simulatedDraw.edges[0].max - simulatedDraw.edges[0].min 
-yDistance = simulatedDraw.edges[1].max - simulatedDraw.edges[1].min 
-xScale = turtleObject.screen.window_width() / xDistance
-yScale = turtleObject.screen.window_height() / yDistance
+for i, lSystem in enumerate(lSystems.LSystems):
+    print(f"{i}: {lSystem.name}")
+lSystemIndex = inputHelper.inputNum(int, "Bitte ein Lindenmayer-System auswählen und die entsprechende Nummer eingeben: ", "Es gibt kein L-System mit dieser Nummer.", 0, len(lSystems.LSystems) - 1)
+lSystem = lSystems.LSystems[lSystemIndex]
+simulatedDraw = drawer.DrawerSimulation(lSystem.productionRules, lSystem.angel, 1, turtle.Vec2D(0, 0), 90.0, turtleObject)
+simulatedDraw.draw(lSystem.startWord, 5)
+maxVec = simulatedDraw.edges.maxVec()
+minVec = simulatedDraw.edges.minVec()
+distance = maxVec - minVec
+xScale = turtleObject.screen.window_width() / distance[0]
+yScale = turtleObject.screen.window_height() / distance[1]
 scale = yScale if xScale > yScale else xScale
-pos = turtle.Vec2D( -(simulatedDraw.edges[0].min + xDistance / 2) * scale, -(simulatedDraw.edges[1].min + yDistance / 2) * scale)
-actualDrawer = drawer.Drawer({"F": "F[+F]F[-F]F"}, 25.7, scale, pos, 90.0, turtleObject)
-actualDrawer.draw("F", 5)
-print(turtleObject.screen._window_size())
+pos = (-minVec - distance * (1/2)) * scale
+print(pos)
+print(distance)
+actualDrawer = drawer.Drawer(lSystem.productionRules, lSystem.angel, scale, pos, 90.0, turtleObject)
+actualDrawer.draw(lSystem.startWord, 5)
 turtleObject.screen.exitonclick()
diff --git a/lindenmayer/drawer.py b/lindenmayer/drawer.py
index 8649af8..c01befd 100644
--- a/lindenmayer/drawer.py
+++ b/lindenmayer/drawer.py
@@ -1,6 +1,5 @@
 import turtle
 from dataclasses import dataclass
-import typing
 
 @dataclass
 class State:
@@ -45,18 +44,24 @@ class Drawer():
 
 class Edges:
     def __init__(self):
-        self.min = 0
-        self.max = 0
+        self.min = [0, 0]
+        self.max = [0, 0]
+    
+    def minVec(self):
+        return turtle.Vec2D(self.min[0], self.min[1])
+
+    def maxVec(self):
+        return turtle.Vec2D(self.max[0], self.max[1])
 
 class DrawerSimulation(Drawer):
     def __init__(self, productionRules, angel, forwardDistance, startPosition, startRotation, turtle):
         super(DrawerSimulation, self).__init__(productionRules, angel, forwardDistance, startPosition, startRotation, turtle)
         self.turtle.penup()
-        self.edges = [Edges(), Edges()]
+        self.edges = Edges()
 
     def storeEdges(self):
         for i, koord in enumerate(self.turtle.position()):
-            if koord < self.edges[i].min:
-                self.edges[i].min = koord
-            elif koord > self.edges[i].max:
-                self.edges[i].max = koord
+            if koord < self.edges.min[i]:
+                self.edges.min[i] = koord
+            elif koord > self.edges.max[i]:
+                self.edges.max[i] = koord
diff --git a/lindenmayer/input.py b/lindenmayer/input.py
new file mode 100644
index 0000000..4a6af52
--- /dev/null
+++ b/lindenmayer/input.py
@@ -0,0 +1,13 @@
+def inputInt(description, indexErrorMsg):
+    lSystemIndex: int
+    while inputError:
+        try:
+            lSystemIndex = int(input(description))
+        except ValueError:
+            print("Fehler: keine gültige Zahl")
+            continue
+        inputError = lSystemIndex < 0 or lSystemIndex >= len(lSystems.LSystems)
+        if inputError:
+            print(indexErrorMsg)
+
+    return lSystemIndex
diff --git a/lindenmayer/inputHelper.py b/lindenmayer/inputHelper.py
new file mode 100644
index 0000000..5ba8cf2
--- /dev/null
+++ b/lindenmayer/inputHelper.py
@@ -0,0 +1,17 @@
+def inputNum(inputType, description, rangeErrorMsg, minRange, maxRange, defaultValue = None):
+    n: int
+    inputError = True
+    while inputError:
+        inputValue = input(description)
+        try:
+            n = inputType(inputValue)
+        except ValueError:
+            if inputValue == "" and defaultValue != None:
+                return defaultValue
+            print("Fehler: keine gültige Zahl")
+            continue
+        inputError = n < minRange or n > maxRange
+        if inputError:
+            print(rangeErrorMsg)
+
+    return n
diff --git a/lindenmayer/lSystems.py b/lindenmayer/lSystems.py
new file mode 100644
index 0000000..0153ed4
--- /dev/null
+++ b/lindenmayer/lSystems.py
@@ -0,0 +1,18 @@
+from dataclasses import dataclass
+import typing
+
+@dataclass
+class LSytem:
+    name: str
+    startWord: str
+    productionRules: typing.Dict[str, str]
+    angel: float
+
+LSystems = [
+        LSytem("AB a", "F", {"F": "F[+F]F[-F]F"}, 25.7),
+        LSytem("AB b", "F", {"F": "F[+F]F[-F][F]"}, 20.0),
+        LSytem("AB c", "F", {"F": "FF-[-F+F+F]+[+F-F-F]"}, 22.5),
+        LSytem("AB d", "X", {"X": "F[+X]F[-X]+X", "F": "FF"}, 20.0),
+        LSytem("AB e", "X", {"X": "F[+X][-X]FX", "F": "FF"}, 25.7),
+        LSytem("AB f", "X", {"X": "F-[[X]+X]+F[+FX]-X", "F": "FF"}, 22.5),
+        ]