diff --git a/.idea/misc.xml b/.idea/misc.xml
index 0548357..cf25bf6 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_13" default="true" project-jdk-name="13.0.2" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/out/production/udemyScala/exercises/expressionExercises$.class b/out/production/udemyScala/exercises/expressionExercises$.class
index 834197e..b702726 100644
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diff --git a/out/production/udemyScala/exercises/expressionExercises.class b/out/production/udemyScala/exercises/expressionExercises.class
index 117a83e..f6b784c 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/Expressions$.class b/out/production/udemyScala/lectures/part1basics/Expressions$.class
index c65c662..e912361 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/Expressions.class b/out/production/udemyScala/lectures/part1basics/Expressions.class
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diff --git a/out/production/udemyScala/lectures/part1basics/Functions$.class b/out/production/udemyScala/lectures/part1basics/Functions$.class
index 566aacd..a599a3f 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/IsNotPrimeException$.class b/out/production/udemyScala/lectures/part1basics/IsNotPrimeException$.class
index 40bcf4c..50de499 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/IsNotPrimeException.class b/out/production/udemyScala/lectures/part1basics/IsNotPrimeException.class
index 4fda7b1..921fc8b 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/IsPrimeException$.class b/out/production/udemyScala/lectures/part1basics/IsPrimeException$.class
index aa6f50d..4ddd248 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/IsPrimeException.class b/out/production/udemyScala/lectures/part1basics/IsPrimeException.class
index 5aec309..6661562 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/Recursion$.class b/out/production/udemyScala/lectures/part1basics/Recursion$.class
index 71cf343..68a45e3 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/Recursion.class b/out/production/udemyScala/lectures/part1basics/Recursion.class
index 1b5c367..80dfe85 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/ValuesVariablesTypes$.class b/out/production/udemyScala/lectures/part1basics/ValuesVariablesTypes$.class
index 13f2d59..f02ac8c 100644
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diff --git a/out/production/udemyScala/lectures/part1basics/ValuesVariablesTypes.class b/out/production/udemyScala/lectures/part1basics/ValuesVariablesTypes.class
index 15d9b9d..2c51cc5 100644
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diff --git a/out/production/udemyScala/playground/JavaPlayground.class b/out/production/udemyScala/playground/JavaPlayground.class
index c3aad2b..e79b298 100644
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diff --git a/out/production/udemyScala/playground/ScalaPlayground$.class b/out/production/udemyScala/playground/ScalaPlayground$.class
index 8eaa217..094ca31 100644
Binary files a/out/production/udemyScala/playground/ScalaPlayground$.class and b/out/production/udemyScala/playground/ScalaPlayground$.class differ
diff --git a/out/production/udemyScala/playground/ScalaPlayground.class b/out/production/udemyScala/playground/ScalaPlayground.class
index 022d785..f448c43 100644
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diff --git a/src/exercises/MyList.scala b/src/exercises/MyList.scala
new file mode 100644
index 0000000..484e006
--- /dev/null
+++ b/src/exercises/MyList.scala
@@ -0,0 +1,83 @@
+package exercises
+
+abstract class MyList (val ints : Array[Int]) {
+
+  def head: Int = ints(0)
+
+  def tail = (ints.slice(1,ints.length))
+
+  def isEmpty: Boolean = ints.length == 0
+
+  def add(i: Int):Array[Int] = ints :+ i
+
+  override def toString: String = {
+    loop(ints, "(") + ")"
+  }
+
+  private def loop(rest: Array[Int], acc: String): String = {
+    if (rest.length != 1) return acc
+    else {
+      loop(rest.slice(1,rest.length) , acc + s"${rest.head}")
+    }
+
+  }
+  /*
+  implement collection
+  single linked list holds int's
+  head = first element of list
+  tail = remainder of the list
+  isEmpty = boolean
+  add(int) => new List with element added
+  override toString => a string representation of the list
+   */
+}
+
+//i'm an idiot
+
+abstract class TrueList {
+  def head: Int
+  def tail: TrueList
+  def isEmpty: Boolean
+  def add(element: Int): TrueList
+
+  //polymorphic
+  def printElements: String
+
+  override def toString: String = s"[$printElements]"
+}
+
+object Empty extends TrueList {
+  override def head: Int = throw new NoSuchElementException
+
+  override def tail: TrueList = throw new NoSuchElementException
+
+  override def isEmpty: Boolean = true
+
+  override def add(element: Int): TrueList = new Cons(element, Empty)
+
+  override def printElements: String = ""
+}
+
+
+class Cons(h: Int, t: TrueList) extends TrueList {
+  override def head: Int = h
+
+  override def tail: TrueList = t
+
+  override def isEmpty: Boolean = false
+
+  override def add(element: Int): TrueList = new Cons(element, this)
+
+  override def printElements: String = if (t.isEmpty) "" + h else s"$h ${t.printElements}"
+}
+
+
+
+object ListTest extends App {
+  val list = new Cons(1, new Cons(2, new Cons(3, Empty)))
+  println(list.tail.head)
+  println(list.add(4).head)
+  println(list.isEmpty)
+
+  println(list.toString)
+}
\ No newline at end of file
diff --git a/src/lectures/part1basics/Functions.scala b/src/lectures/part1basics/Functions.scala
index 4cf0aa0..0645285 100644
--- a/src/lectures/part1basics/Functions.scala
+++ b/src/lectures/part1basics/Functions.scala
@@ -62,7 +62,7 @@ object Functions extends App {
 
   def isPrime(n: Int) : Boolean = {
     def checkNum(m: Int) : Int = {
-      if (m <= 1) throw IsPrimeException("Finished, it is prime")
+      if (m <= 1) throw IsPrimeException()
       if (n % m == 0 && m != 1) throw IsNotPrimeException(m + "")
       else checkNum(m-1)
     }
@@ -86,6 +86,6 @@ object Functions extends App {
 
 }
 
-case class IsPrimeException(value: "Finished, it is prime") extends Throwable
+case class IsPrimeException() extends Throwable
 
 case class IsNotPrimeException(str: String) extends Throwable
diff --git a/src/lectures/part1basics/Recursion.scala b/src/lectures/part1basics/Recursion.scala
index 6a7e761..3c65562 100644
--- a/src/lectures/part1basics/Recursion.scala
+++ b/src/lectures/part1basics/Recursion.scala
@@ -52,7 +52,7 @@ object Recursion extends App {
   def isPrime(n: Int) : Boolean = {
     @tailrec
     def checkNum(m: Int) : Int = {
-      if (m <= 1) throw IsPrimeException("Finished, it is prime")
+      if (m <= 1) throw IsPrimeException()
       if (n % m == 0 && m != 1) throw IsNotPrimeException(m + "")
       else checkNum(m-1)
     }
diff --git a/src/lectures/part2oop/AbstractDataTypes.scala b/src/lectures/part2oop/AbstractDataTypes.scala
new file mode 100644
index 0000000..6d684ec
--- /dev/null
+++ b/src/lectures/part2oop/AbstractDataTypes.scala
@@ -0,0 +1,49 @@
+package lectures.part2oop
+
+object AbstractDataTypes extends App {
+
+  // abstract
+  abstract class Animal {
+    val creatureType: String = "wild"
+    def eat: Unit
+  }
+
+  class Dog extends Animal {
+    override val creatureType: String = "Canine"
+
+    def eat: Unit = println("crunch crunch")
+  }
+
+
+  // traits
+  trait Carnivore {
+    def eat(animal: Animal): Unit
+    val preferedMeal: String = "fresh meat"
+  }
+
+
+  trait ColdBlooded
+  class Crocodile extends Animal with Carnivore with ColdBlooded {
+    override val creatureType: String = "croc"
+
+    override def eat: Unit = println("nomnomnom")
+
+    override def eat(animal: Animal): Unit = println(s"i'm a croc and i'm eating ${animal.creatureType}")
+  }
+
+  val dog = new Dog
+  val croc = new Crocodile
+  croc.eat(dog)
+
+
+
+
+  // traits vs abstract classes
+
+  // 1 traits do not have constructor parameters
+
+  // 2 can only extend 1 class, but can extend multiple traits (same class)
+
+  // 3 traits are meant to describe behavior, abstract class describes a thing
+
+}
diff --git a/src/lectures/part2oop/package.scala b/src/lectures/part2oop/package.scala
new file mode 100644
index 0000000..fceb207
--- /dev/null
+++ b/src/lectures/part2oop/package.scala
@@ -0,0 +1,8 @@
+package lectures
+
+object Inheritance extends App {
+
+
+
+
+}
diff --git a/udemyScala.iml b/udemyScala.iml
index 25bc755..775b614 100644
--- a/udemyScala.iml
+++ b/udemyScala.iml
@@ -8,5 +8,6 @@
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
     <orderEntry type="library" name="scala-sdk-2.13.1" level="application" />
+    <orderEntry type="library" name="scala-sdk-2.12.7" level="application" />
   </component>
 </module>
\ No newline at end of file