diff --git a/build.sbt b/build.sbt
index 9c3b3e8..a83befd 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,26 +4,37 @@ version := "0.1"
 
 scalaVersion := "2.12.6"
 
-resolvers += Resolver.sonatypeRepo("releases")
-
 addCompilerPlugin("org.spire-math" %% "kind-projector" % "0.9.7")
 
-version                   := "0.1"
-fork in Test              := true
-parallelExecution in Test := false
-organizationName          := "Fluence Labs Limited"
-organizationHomepage      := Some(new URL("https://fluence.one"))
-startYear                 := Some(2018)
-licenses += ("Apache-2.0", new URL("https://www.apache.org/licenses/LICENSE-2.0.txt"))
-//headerLicense := Some(License.ALv2("2018", organizationName.value))
-resolvers += Resolver.bintrayRepo("fluencelabs", "releases")
-scalafmtOnCompile := true
+val commons = Seq(
+  version                   := "0.1",
+  fork in Test              := true,
+  parallelExecution in Test := false,
+  organizationName          := "Fluence Labs Limited",
+  organizationHomepage      := Some(new URL("https://fluence.one")),
+  startYear                 := Some(2018),
+  licenses += ("Apache-2.0", new URL("https://www.apache.org/licenses/LICENSE-2.0.txt")),
+//headerLicense := Some(License.ALv2("2018", organizationName.value)),
+  resolvers += Resolver.bintrayRepo("fluencelabs", "releases"),
+  resolvers += Resolver.sonatypeRepo("releases"),
+  scalafmtOnCompile := true,
 // see good explanation https://gist.github.com/djspiewak/7a81a395c461fd3a09a6941d4cd040f2
-scalacOptions += "-Ypartial-unification"
+  scalacOptions += "-Ypartial-unification"
+)
 
-libraryDependencies ++= Seq(
-  "org.typelevel"       %% "cats-core"   % "1.2.0",
-  "org.typelevel"       %% "cats-free"   % "1.2.0",
-  "com.chuusai" %% "shapeless" % "2.3.3",
-  "org.scalatest" %% "scalatest"   % "3.0.5"  % Test
-)
\ No newline at end of file
+commons
+
+lazy val core = project.settings(
+  commons,
+  libraryDependencies ++= Seq(
+    "org.typelevel" %% "cats-core" % "1.2.0",
+    "org.typelevel" %% "cats-free" % "1.2.0",
+    "com.chuusai"   %% "shapeless" % "2.3.3",
+    "org.scalatest" %% "scalatest" % "3.0.5" % Test
+  )
+)
+
+lazy val root = project
+  .in(file("."))
+  .dependsOn(core)
+  .aggregate(core)
diff --git a/src/main/scala/fluence/hackethberlin/CodeChunk.scala b/core/src/main/scala/fluence/hackethberlin/CodeChunk.scala
similarity index 97%
rename from src/main/scala/fluence/hackethberlin/CodeChunk.scala
rename to core/src/main/scala/fluence/hackethberlin/CodeChunk.scala
index d6f06d8..6d487ca 100644
--- a/src/main/scala/fluence/hackethberlin/CodeChunk.scala
+++ b/core/src/main/scala/fluence/hackethberlin/CodeChunk.scala
@@ -1,7 +1,7 @@
 package fluence.hackethberlin
 
 import cats.data.Writer
-import cats.{~>, Monad, Monoid}
+import cats.{~>, Monoid}
 
 import scala.collection.immutable.Queue
 
diff --git a/src/main/scala/fluence/hackethberlin/Decorator.scala b/core/src/main/scala/fluence/hackethberlin/Decorator.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/Decorator.scala
rename to core/src/main/scala/fluence/hackethberlin/Decorator.scala
diff --git a/src/main/scala/fluence/hackethberlin/Expr.scala b/core/src/main/scala/fluence/hackethberlin/Expr.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/Expr.scala
rename to core/src/main/scala/fluence/hackethberlin/Expr.scala
diff --git a/src/main/scala/fluence/hackethberlin/FuncDef.scala b/core/src/main/scala/fluence/hackethberlin/FuncDef.scala
similarity index 70%
rename from src/main/scala/fluence/hackethberlin/FuncDef.scala
rename to core/src/main/scala/fluence/hackethberlin/FuncDef.scala
index 0a58368..b2641c7 100644
--- a/src/main/scala/fluence/hackethberlin/FuncDef.scala
+++ b/core/src/main/scala/fluence/hackethberlin/FuncDef.scala
@@ -1,15 +1,13 @@
 package fluence.hackethberlin
 
-import cats.Monad
 import fluence.hackethberlin.types.{DataVyper, ProductType}
 import shapeless._
 import cats.free.Free
-import cats.syntax.functor._
 
 class FuncDef[Args <: HList, Ret <: types.Type](
   name: String,
   argsDef: ProductType[Args],
-  ret: Option[Ret],
+  ret: Ret,
   body: ProductType[Args] ⇒ Free[Expr, Ret],
   decorators: Set[Decorator] = Set.empty
 ) {
@@ -18,10 +16,14 @@ class FuncDef[Args <: HList, Ret <: types.Type](
     body(argsDef).foldMap(CodeChunk.fromExpr).run._1.toVyper(1)
 
   def toVyper: String =
-    s"${decorators.map(_.toVyper).mkString("\n")}\ndef $name(${argsDef.toArgsVyper})${ret.fold("")(" -> " + _.toVyper)}:\n$bodyVyper\n"
+    s"${decorators.map(_.toVyper).mkString("\n")}\ndef $name(${argsDef.toArgsVyper})${Option(ret)
+      .filter(_ != types.Void)
+      .fold("")(" -> " + _.toVyper)}:\n$bodyVyper\n"
 
   def @:(decorator: Decorator): FuncDef[Args, Ret] =
     new FuncDef[Args, Ret](name, argsDef, ret, body, decorators + decorator)
+
+  //def apply[Params <: HList](params: Params)(implicit a: LUBConstraint s: ops.hlist.Mapped[Args, InlineExpr]): InlineExpr[Ret] = ???
 }
 
 object FuncDef {
@@ -31,12 +33,12 @@ object FuncDef {
     argsDef: Args,
     ret: Ret
   )(body: ProductType[Args] ⇒ Free[Expr, Ret]): FuncDef[Args, Ret] =
-    new FuncDef(name, ProductType(argsDef), Some(ret), body)
+    new FuncDef(name, ProductType(argsDef), ret, body)
 
   def apply[Args <: HList: DataVyper](
     name: String,
     argsDef: Args
   )(body: ProductType[Args] ⇒ Free[Expr, Unit]): FuncDef[Args, types.Void] =
-    new FuncDef(name, ProductType(argsDef), None, args ⇒ body(args).map(_ ⇒ types.Void))
+    new FuncDef(name, ProductType(argsDef), types.Void, args ⇒ body(args).map(_ ⇒ types.Void))
 
 }
diff --git a/src/main/scala/fluence/hackethberlin/types/DataVyper.scala b/core/src/main/scala/fluence/hackethberlin/types/DataVyper.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/types/DataVyper.scala
rename to core/src/main/scala/fluence/hackethberlin/types/DataVyper.scala
diff --git a/src/main/scala/fluence/hackethberlin/types/Mapping.scala b/core/src/main/scala/fluence/hackethberlin/types/Mapping.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/types/Mapping.scala
rename to core/src/main/scala/fluence/hackethberlin/types/Mapping.scala
diff --git a/src/main/scala/fluence/hackethberlin/types/PrimitiveType.scala b/core/src/main/scala/fluence/hackethberlin/types/PrimitiveType.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/types/PrimitiveType.scala
rename to core/src/main/scala/fluence/hackethberlin/types/PrimitiveType.scala
diff --git a/src/main/scala/fluence/hackethberlin/types/ProductType.scala b/core/src/main/scala/fluence/hackethberlin/types/ProductType.scala
similarity index 95%
rename from src/main/scala/fluence/hackethberlin/types/ProductType.scala
rename to core/src/main/scala/fluence/hackethberlin/types/ProductType.scala
index 820a7f0..bb197be 100644
--- a/src/main/scala/fluence/hackethberlin/types/ProductType.scala
+++ b/core/src/main/scala/fluence/hackethberlin/types/ProductType.scala
@@ -23,7 +23,7 @@ class ProductType[D <: HList](dataDef: D, dv: DataVyper[D]) extends Type {
     dv.toVyperDefinitions(dataDef).mkString(", ")
 
   def funcDef[Ret <: Type](name: String, ret: Ret)(body: ProductType[D] ⇒ Free[Expr, Ret]): FuncDef[D, Ret] =
-    new FuncDef[D, Ret](name, this, Some(ret), body)
+    new FuncDef[D, Ret](name, this, ret, body)
 
 }
 
diff --git a/src/main/scala/fluence/hackethberlin/types/Type.scala b/core/src/main/scala/fluence/hackethberlin/types/Type.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/types/Type.scala
rename to core/src/main/scala/fluence/hackethberlin/types/Type.scala
diff --git a/src/main/scala/fluence/hackethberlin/types/Void.scala b/core/src/main/scala/fluence/hackethberlin/types/Void.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/types/Void.scala
rename to core/src/main/scala/fluence/hackethberlin/types/Void.scala
diff --git a/src/main/scala/fluence/hackethberlin/types/package.scala b/core/src/main/scala/fluence/hackethberlin/types/package.scala
similarity index 100%
rename from src/main/scala/fluence/hackethberlin/types/package.scala
rename to core/src/main/scala/fluence/hackethberlin/types/package.scala
diff --git a/src/main/scala/fluence/hackethberlin/MakeVyperApp.scala b/src/main/scala/fluence/MakeVyperApp.scala
similarity index 95%
rename from src/main/scala/fluence/hackethberlin/MakeVyperApp.scala
rename to src/main/scala/fluence/MakeVyperApp.scala
index a7fa284..3c94ad5 100644
--- a/src/main/scala/fluence/hackethberlin/MakeVyperApp.scala
+++ b/src/main/scala/fluence/MakeVyperApp.scala
@@ -1,9 +1,9 @@
-package fluence.hackethberlin
+package fluence
 
+import hackethberlin._
+import hackethberlin.types._
 import shapeless._
-import types._
 import Decorator._
-import cats.free.Free
 import syntax.singleton._
 
 object MakeVyperApp extends App {