diff --git a/.mill-version b/.mill-version
deleted file mode 100644
index e2e3067..0000000
--- a/.mill-version
+++ /dev/null
@@ -1 +0,0 @@
-0.12.7
diff --git a/Makefile b/Makefile
index d87e7c0..a8b43f9 100644
--- a/Makefile
+++ b/Makefile
@@ -1,17 +1,15 @@
 BUILD_DIR = ./build
 
-PRJ = playground
-
 test:
-	mill -i $(PRJ).test
+	mill -i test
 
 verilog:
 	$(call git_commit, "generate verilog")
 	mkdir -p $(BUILD_DIR)
-	mill -i $(PRJ).runMain Elaborate --target-dir $(BUILD_DIR)
+	mill -i runMain Elaborate --target-dir $(BUILD_DIR)
 
 help:
-	mill -i $(PRJ).runMain Elaborate --help
+	mill -i runMain Elaborate --help
 
 reformat:
 	mill -i __.reformat
diff --git a/README.md b/README.md
index 507cee4..f108591 100644
--- a/README.md
+++ b/README.md
@@ -9,12 +9,12 @@ Contents at a glance:
 * `.gitignore` - helps Git ignore junk like generated files, build products, and temporary files.
 * `build.mill` - instructs mill to build the Chisel project
 * `Makefile` - rules to call mill
-* `playground/src/GCD.scala` - GCD source file
-* `playground/src/DecoupledGCD.scala` - another GCD source file
-* `playground/src/Elaborate.scala` - wrapper file to call chisel command with the GCD module
-* `playground/test/src/GCDSpec.scala` - GCD tester
+* `src/GCD.scala` - GCD source file
+* `src/DecoupledGCD.scala` - another GCD source file
+* `src/Elaborate.scala` - wrapper file to call chisel command with the GCD module
+* `test/src/GCDSpec.scala` - GCD tester
 
-Feel free to rename or delete files under `playground/` or use them as a reference/template.
+Feel free to rename or delete files under `src/` and `test/` or use them as a reference/template.
 
 ## Getting Started
 
diff --git a/build.mill b/build.mill
index 38595ca..acc1c91 100644
--- a/build.mill
+++ b/build.mill
@@ -1,17 +1,14 @@
+//| mill-version: 1.0.6
+
 package build
 
-// import Mill dependency
 import mill._
-import mill.define.Sources
-import mill.modules.Util
 import mill.scalalib.scalafmt.ScalafmtModule
 import mill.scalalib.TestModule.ScalaTest
 import mill.scalalib._
-// support BSP
-import mill.bsp._
 
-object playground extends ScalaModule with ScalafmtModule { m =>
-  override def scalaVersion = "2.13.15"
+object `package` extends ScalaModule with ScalafmtModule { m =>
+  override def scalaVersion = "2.13.18"
 
   override def scalacOptions = Seq(
     "-language:reflectiveCalls",
@@ -20,22 +17,14 @@ object playground extends ScalaModule with ScalafmtModule { m =>
     "-Xcheckinit"
   )
 
-  override def ivyDeps             = Agg(ivy"org.chipsalliance::chisel:6.6.0")
-  override def scalacPluginIvyDeps = Agg(ivy"org.chipsalliance:::chisel-plugin:6.6.0")
+  override def mvnDeps             = Seq(mvn"org.chipsalliance::chisel:7.6.0")
+  override def scalacPluginMvnDeps = Seq(mvn"org.chipsalliance:::chisel-plugin:7.6.0")
 
   object test extends ScalaTests with TestModule.ScalaTest with ScalafmtModule {
-    override def ivyDeps = m.ivyDeps() ++ Agg(
-      ivy"org.scalatest::scalatest::3.2.19",
+    override def mvnDeps = m.mvnDeps() ++ Seq(
+      mvn"org.scalatest::scalatest::3.2.19",
       // for formal flow in future
-      ivy"edu.berkeley.cs::chiseltest:6.0.0"
+      mvn"edu.berkeley.cs::chiseltest:6.0.0"
     )
   }
-
-  def repositoriesTask = Task.Anon {
-    Seq(
-      coursier.MavenRepository("https://repo.scala-sbt.org/scalasbt/maven-releases"),
-      coursier.MavenRepository("https://oss.sonatype.org/content/repositories/releases"),
-      coursier.MavenRepository("https://oss.sonatype.org/content/repositories/snapshots")
-    ) ++ super.repositoriesTask()
-  }
 }
diff --git a/playground/src/DecoupledGCD.scala b/src/DecoupledGCD.scala
similarity index 100%
rename from playground/src/DecoupledGCD.scala
rename to src/DecoupledGCD.scala
diff --git a/playground/src/Elaborate.scala b/src/Elaborate.scala
similarity index 100%
rename from playground/src/Elaborate.scala
rename to src/Elaborate.scala
diff --git a/playground/src/GCD.scala b/src/GCD.scala
similarity index 100%
rename from playground/src/GCD.scala
rename to src/GCD.scala
diff --git a/playground/test/src/GCDSpec.scala b/test/src/GCDSpec.scala
similarity index 100%
rename from playground/test/src/GCDSpec.scala
rename to test/src/GCDSpec.scala