diff -r c0cf0150cb4c -r 040b435ce0dd build.sc
--- a/build.sc	Sat Dec 26 20:04:48 2020 +0100
+++ b/build.sc	Sat Dec 26 20:15:08 2020 +0100
@@ -17,13 +17,17 @@
 
 object V {
   val app = "0.3-SNAPSHOT"
-  val scalaJs = "0.6.33"
   val scala211 = "2.11.12"
   val scala212 = "2.12.12"
+  val scala213 = "2.13.4"
+  val scalaJs06 = "0.6.33"
+  val scalaJs = "1.3.1"
+  val scalatags = "0.9.2"
 }
 
 object D {
-  val scalatags = ivy"com.lihaoyi::scalatags::0.6.8"
+  val scalatags211 = ivy"com.lihaoyi::scalatags::0.6.8"
+  val scalatags = ivy"com.lihaoyi::scalatags::${V.scalatags}"
 }
 
 trait Common extends CrossSbtModule with PublishModule {
@@ -53,7 +57,6 @@
     "-language:postfixOps",
     "-unchecked",                        // Enable additional warnings where generated code depends on assumptions.
     "-Xcheckinit",                       // Wrap field accessors to throw an exception on uninitialized access.
-    "-Xfuture",                          // Turn on future language features.
     "-target:jvm-1.8"
   )}
 
@@ -71,7 +74,9 @@
       maskedTags contains v).headOption
   }
 
-  override def ivyDeps: Target[Loose.Agg[Dep]] = Agg(D.scalatags)
+  override def ivyDeps: Target[Loose.Agg[Dep]] = T{
+    if (scalaVersion() == V.scala211) Agg(D.scalatags211) else Agg(D.scalatags)
+  }
 
   override def sources: Sources = T.sources{
     super.sources() :+ PathRef(millSourcePath / 'shared / 'src / 'main / 'scala)
@@ -84,35 +89,55 @@
 }
 
 class JvmModule(val crossScalaVersion: String) extends Common
-class JsModule(val crossScalaVersion: String) extends ScalaJSModule
-  with Common {
-  override def scalaJSVersion: Target[String] = V.scalaJs
+class JsModule(val crossScalaVersion: String, crossJSVersion: String)
+  extends ScalaJSModule with Common {
+
+  override def scalaJSVersion: Target[String] = crossJSVersion
+
+  override def millSourcePath = super.millSourcePath / os.up
 }
 
-object jvm extends Cross[JvmModule](V.scala211, V.scala212)
-object js extends Cross[JsModule](V.scala211, V.scala212)
+object jvm extends Cross[JvmModule](V.scala211, V.scala212, V.scala213)
+object js extends Cross[JsModule](
+  V.scala211 -> V.scalaJs06,
+  V.scala212 -> V.scalaJs06,
+  V.scala212 -> V.scalaJs,
+  V.scala213 -> V.scalaJs06,
+  V.scala213 -> V.scalaJs
+)
 
 def compileAll(): Command[Unit] = T.command{
+  jvm(V.scala213).compile()
+  js(V.scala213, V.scalaJs).compile()
+  js(V.scala213, V.scalaJs06).compile()
   jvm(V.scala212).compile()
-  js(V.scala212).compile()
+  js(V.scala212, V.scalaJs).compile()
+  js(V.scala212, V.scalaJs06).compile()
   jvm(V.scala211).compile()
-  js(V.scala211).compile()
+  js(V.scala211, V.scalaJs06).compile()
   ()
 }
 
 def publishLocal(): Command[Unit] = T.command{
+  jvm(V.scala213).publishLocal()()
+  js(V.scala213, V.scalaJs).publishLocal()()
+  js(V.scala213, V.scalaJs06).publishLocal()()
   jvm(V.scala212).publishLocal()()
-  js(V.scala212).publishLocal()()
+  js(V.scala212, V.scalaJs).publishLocal()()
+  js(V.scala212, V.scalaJs06).publishLocal()()
   jvm(V.scala211).publishLocal()()
-  js(V.scala211).publishLocal()()
-  ()
+  js(V.scala211, V.scalaJs06).publishLocal()()
 }
 
 def publishM2Local(p: os.Path): Command[Unit] = T.command{
+  jvm(V.scala213).publishM2Local(p.toString)()
+  js(V.scala213, V.scalaJs).publishM2Local(p.toString)()
+  js(V.scala213, V.scalaJs06).publishM2Local(p.toString)()
   jvm(V.scala212).publishM2Local(p.toString)()
-  js(V.scala212).publishM2Local(p.toString)()
+  js(V.scala212, V.scalaJs).publishM2Local(p.toString)()
+  js(V.scala212, V.scalaJs06).publishM2Local(p.toString)()
   jvm(V.scala211).publishM2Local(p.toString)()
-  js(V.scala211).publishM2Local(p.toString)()
+  js(V.scala211, V.scalaJs06).publishM2Local(p.toString)()
   ()
 }