diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9d284295..39b9fb17 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,7 +23,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.12.13, 2.13.4]
+        scala: [2.12.13, 2.13.4, 3.0.0-RC1]
         java: [adopt@1.8]
     runs-on: ${{ matrix.os }}
     steps:
@@ -71,7 +71,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.12.12]
+        scala: [2.13.4]
         java: [adopt@1.8]
     runs-on: ${{ matrix.os }}
     steps:
@@ -117,6 +117,16 @@ jobs:
           tar xf targets.tar
           rm targets.tar
 
+      - name: Download target directories (3.0.0-RC1)
+        uses: actions/download-artifact@v2
+        with:
+          name: target-${{ matrix.os }}-3.0.0-RC1-${{ matrix.java }}
+
+      - name: Inflate target directories (3.0.0-RC1)
+        run: |
+          tar xf targets.tar
+          rm targets.tar
+
       - uses: olafurpg/setup-gpg@v3
 
       - env:
diff --git a/build.sbt b/build.sbt
index cd4737f5..f7b5023e 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,17 +4,13 @@ import sbtcrossproject.CrossPlugin.autoImport.crossProject
 
 ThisBuild / githubWorkflowPublishTargetBranches := Seq()
 
-ThisBuild / crossScalaVersions := Seq("2.12.13", "2.13.4")
+ThisBuild / crossScalaVersions := Seq("2.12.13", "2.13.4", "3.0.0-RC1")
 
-lazy val commonSettings = Def.settings(
-  scalaVersion := "2.13.1",
-  crossScalaVersions := (ThisBuild / crossScalaVersions).value
-)
+ThisBuild / scalaVersion := "2.13.4"
 
 lazy val root = project.in(file(".")).aggregate(js, jvm).
   settings(
     name := "mouse",
-    commonSettings,
     publish / skip := true,
     sonatypeProfileName := "org.typelevel",
     releaseCrossBuild := true
@@ -24,13 +20,11 @@ lazy val cross = crossProject(JSPlatform, JVMPlatform).in(file(".")).
   settings(
     name := "mouse",
     organization := "org.typelevel",
-    commonSettings,
     sonatypeProfileName := "org.typelevel",
     libraryDependencies ++= Seq(
       "org.typelevel" %%% "cats-core" % "2.4.2",
       "org.scalatest" %%% "scalatest" % "3.2.5" % Test,
-      "org.scalatestplus" %%% "scalacheck-1-15" % "3.2.5.0" % Test,
-      compilerPlugin("org.typelevel" %% "kind-projector" % "0.11.3" cross CrossVersion.full)
+      "org.scalatestplus" %%% "scalacheck-1-15" % "3.2.5.0" % Test
     ),
     licenses += ("MIT license", url("http://opensource.org/licenses/MIT")),
     homepage := Some(url("https://github.com/typelevel/mouse")),
@@ -39,11 +33,19 @@ lazy val cross = crossProject(JSPlatform, JVMPlatform).in(file(".")).
     scalacOptions ++= Seq("-feature", "-deprecation", "-language:implicitConversions", "-language:higherKinds"),
     scalacOptions ++= {
       scalaVersion.value match {
-        case v if v.startsWith("2.13") => Nil
-        case _ => Seq("-Ypartial-unification")
+        case v if v.startsWith("2.12") => Seq("-Ypartial-unification")
+        case v if v.startsWith("3") => Seq("-source", "3.0-migration")
+        case _ => Nil
       }
     },
     Test / publishArtifact := false,
+    Compile / doc / sources := {
+      val old = (Compile / doc / sources).value
+      if (isDotty.value)
+        Seq()
+      else
+        old
+    },
     pomIncludeRepository := { _ => false },
     releasePublishArtifactsAction := PgpKeys.publishSigned.value,
     releaseProcess := Seq[ReleaseStep](
@@ -59,6 +61,10 @@ lazy val cross = crossProject(JSPlatform, JVMPlatform).in(file(".")).
       commitNextVersion,
     )
   )
+  .jsSettings(
+    crossScalaVersions := (ThisBuild / crossScalaVersions).value.filter(_.startsWith("2")),
+    publishConfiguration := publishConfiguration.value.withOverwrite(true)
+  )
 
 ThisBuild / githubWorkflowTargetTags ++= Seq("v*")
 ThisBuild / githubWorkflowPublishTargetBranches :=
diff --git a/project/plugins.sbt b/project/plugins.sbt
index cdcc89b4..9321028e 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -5,3 +5,4 @@ addSbtPlugin("com.github.gseitz" % "sbt-release" % "1.0.11")
 addSbtPlugin("org.portable-scala" % "sbt-scalajs-crossproject" % "1.0.0")
 addSbtPlugin("com.codecommit" % "sbt-github-actions" % "0.10.1")
 addSbtPlugin("com.geirsson" % "sbt-ci-release" % "1.5.5")
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.5.3")
diff --git a/shared/src/test/scala/mouse/AnyFSyntaxTest.scala b/shared/src/test/scala/mouse/AnyFSyntaxTest.scala
index 10ed6e8d..4c3a7104 100644
--- a/shared/src/test/scala/mouse/AnyFSyntaxTest.scala
+++ b/shared/src/test/scala/mouse/AnyFSyntaxTest.scala
@@ -6,19 +6,36 @@ import cats.{Id, ~>}
 
 class AnyFSyntaxTest extends MouseSuite {
 
-  val emptyK: List ~> List = λ[List ~> List](_ => Nil)
+  val emptyK = new (List ~> List) {
+    def apply[A](x: List[A]) = Nil
+  }
 
-  val double: List ~> List = λ[List ~> List](list => list ::: list)
+  val double = new (List ~> List) {
+    def apply[A](x: List[A]) = x ::: x
+  }
+
+  type E[B] = Either[String, B]
+  val toRight = new (Option ~> E) {
+    def apply[A](x: Option[A]) = x.toRight("foo")
+  }
+
+  val headOption = new (List ~> Option) {
+    def apply[A](x: List[A]) = x.headOption
+  }
+
+  val optionGet = new (Option ~> Id) {
+    def apply[A](x: Option[A]) = x.get
+  }
 
   List(1, 2, 3) thrushK emptyK shouldEqual Nil
 
   List(5, 10) thrushK double shouldEqual List(5, 10, 5, 10)
 
-  "thing".some thrushK (λ[Option ~> Either[String, *]](_.toRight("foo"))) shouldEqual Right(
+  "thing".some thrushK toRight shouldEqual Right(
     "thing"
   )
 
   (List("This") ||> double
-    ||> λ[List ~> Option](_.headOption)
-    ||> λ[Option ~> Id](_.head)) shouldEqual "This"
+    ||> headOption
+    ||> optionGet) shouldEqual "This"
 }
diff --git a/shared/src/test/scala/mouse/MouseSuite.scala b/shared/src/test/scala/mouse/MouseSuite.scala
index f8fe54e1..bcb9a55c 100644
--- a/shared/src/test/scala/mouse/MouseSuite.scala
+++ b/shared/src/test/scala/mouse/MouseSuite.scala
@@ -14,12 +14,12 @@ trait MouseSuite
     with ScalaCheckDrivenPropertyChecks
     with AllSharedSyntax
     with AllInstances {
-  implicit val eq0 = new Eq[NumberFormatException] {
+  implicit val eq0: Eq[NumberFormatException] = new Eq[NumberFormatException] {
     override def eqv(x: NumberFormatException, y: NumberFormatException): Boolean =
       x.getMessage == y.getMessage
   }
 
-  implicit val eq1 = new Eq[IllegalArgumentException] {
+  implicit val eq1: Eq[IllegalArgumentException] = new Eq[IllegalArgumentException] {
     override def eqv(x: IllegalArgumentException, y: IllegalArgumentException): Boolean =
       x.getMessage == y.getMessage
   }