diff --git a/.github/run.sh b/.github/run.sh
index 4079db4..2466e4c 100755
--- a/.github/run.sh
+++ b/.github/run.sh
@@ -8,7 +8,7 @@ no_lint=0
 while (( $# > 0 )); do
    case "$1" in
    	--help)
-			printf "run.sh [OPTION]... [PKG]\n"
+			printf "run.sh [OPTION]... [DIR]\n"
 			printf "options:\n"
 			printf "\t--help			Show help\n"
 			printf "\t--no-test		Skip tests\n"
@@ -29,21 +29,24 @@ while (( $# > 0 )); do
    esac
 done
 
+./mill __.compile
+
 if (( no_test == 0 )); then
   if [[ -z "$1" ]]; then
-    sbt -warn test
+    ./mill __.test
+  elif ./mill resolve problems["$1"].__.test &>/dev/null; then
+    ./mill problems["$1"].__.test
   else
-    green='\033[1;32m'
+    red='\033[0;31m'
     no_color='\033[0m'
-	printf "Running tests in packages matching: %b%s*%b\n" "$green" "$1" "$no_color"
-    sbt -warn "Test / testOnly $1*"
+	  printf "%bNo tests found in: %s%b\n" "$red" "$1" "$no_color"
   fi
 fi
 
 if (( no_lint == 0 )); then
 	if [[ -z "${CI}" ]]; then
-	  sbt -warn scalafmtAll
+	  ./mill mill.scalalib.scalafmt.ScalafmtModule/reformatAll problems[_].sources
 	else
-	  sbt -warn scalafmtCheckAll
+		./mill mill.scalalib.scalafmt.ScalafmtModule/checkFormatAll problems[_].sources
 	fi
 fi
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 49264ae..6a2717d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,12 +8,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: 17
+          java-version: 21
       - name: Test
         run: ./.github/run.sh --no-lint
       - name: Lint
diff --git a/.gitignore b/.gitignore
index 7c2f816..4cf6a63 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,33 +1,31 @@
-# macOS
 .DS_Store
+*.class
+*.log
+*~
 
-# sbt
+# idea
+.idea
+.idea_modules
+/.worksheet/
+
+# mill
+out/
+
+.bsp/
+.metals/
+.vscode/
+.bloop/
+
+# SBT
 dist/*
 target/
 lib_managed/
 src_managed/
 project/boot/
-project/project
 project/plugins/project/
-project/local-plugins.sbt
 .history
-.ensime
-.ensime_cache/
-.sbt-scripted/
-local.sbt
+.cache
+.lib/
 
-# Bloop
-.bsp
-
-# VS Code
-.vscode/
-
-# Metals
-.bloop/
-.metals/
-metals.sbt
-
-# IDEA
-.idea
-.idea_modules
-/.worksheet/
+# virtual machine crash logs
+hs_err_pid*
diff --git a/.mill-version b/.mill-version
new file mode 100644
index 0000000..7fd0b1e
--- /dev/null
+++ b/.mill-version
@@ -0,0 +1 @@
+0.12.4
\ No newline at end of file
diff --git a/.scalafmt.conf b/.scalafmt.conf
index cf5cb5b..449f165 100644
--- a/.scalafmt.conf
+++ b/.scalafmt.conf
@@ -1,4 +1,4 @@
-version = "3.7.17"
+version = "3.8.3"
 align.preset = more
 maxColumn = 120
 runner.dialect = scala3
diff --git a/build.mill b/build.mill
new file mode 100644
index 0000000..a8cf16d
--- /dev/null
+++ b/build.mill
@@ -0,0 +1,35 @@
+package build
+
+import mill._, scalalib._, scalafmt._
+import $packages._
+import $file.{versions => v}
+
+val moduleNames = interp.watchValue(os.list(millSourcePath / "problems").map(_.last))
+
+object problems extends Cross[NineNineModule](moduleNames)
+
+trait NineNineModule extends ScalaModule with Cross.Module[String] with ScalafmtModule {
+
+  val scalaVersion = v.scalaVersion
+  def millSourcePath = super.millSourcePath / crossValue
+
+  def scalacOptions: T[Seq[String]] = Seq(
+    "-encoding", "UTF-8",
+    "-feature",
+    "-Werror",
+    "-explain",
+    "-deprecation",
+    "-unchecked",
+    "-Wunused:all",
+    "-rewrite",
+    "-indent",
+    "-source", "future",
+  )
+
+  object test extends ScalaTests with TestModule.Munit {
+   def ivyDeps = Agg(
+     ivy"org.scalameta::munit:${v.munitVersion}",
+     ivy"org.scalameta::munit-scalacheck:${v.munitScalaCheckVersion}",
+   )
+  }
+}
diff --git a/build.sbt b/build.sbt
deleted file mode 100644
index ba3ee19..0000000
--- a/build.sbt
+++ /dev/null
@@ -1,31 +0,0 @@
-val scala3Version = "3.3.1"
-
-lazy val root = project
-  .in(file("."))
-  .settings(
-    name := "99-scala",
-    version := "1.0.0",
-
-    scalaVersion := scala3Version,
-
-    scalafmtPrintDiff := true,
-
-    libraryDependencies ++= Seq(
-      "org.scalameta" %% "munit" % "1.0.0-M10" % Test,
-      "org.scalameta" %% "munit-scalacheck" % "1.0.0-M10" % Test,
-      // "org.typelevel" %% "cats-core" % "2.10.0"
-    ),
-
-    scalacOptions ++= Seq(
-        "-encoding", "UTF-8",
-        "-feature",
-        "-Werror",
-        "-explain",
-        "-deprecation",
-        "-unchecked",
-        "-Wunused:all",
-        "-rewrite",
-        "-indent",
-        "-source", "future",
-      ),
-  )
diff --git a/mill b/mill
new file mode 100755
index 0000000..44386d6
--- /dev/null
+++ b/mill
@@ -0,0 +1,241 @@
+#!/usr/bin/env sh
+
+# This is a wrapper script, that automatically download mill from GitHub release pages
+# You can give the required mill version with --mill-version parameter
+# If no version is given, it falls back to the value of DEFAULT_MILL_VERSION
+#
+# Original Project page: https://github.com/lefou/millw
+# Script Version: 0.4.12
+#
+# If you want to improve this script, please also contribute your changes back!
+#
+# Licensed under the Apache License, Version 2.0
+
+set -e
+
+if [ -z "${DEFAULT_MILL_VERSION}" ] ; then
+  DEFAULT_MILL_VERSION=0.12.4
+fi
+
+
+if [ -z "${GITHUB_RELEASE_CDN}" ] ; then
+  GITHUB_RELEASE_CDN=""
+fi
+
+
+MILL_REPO_URL="https://github.com/com-lihaoyi/mill"
+
+if [ -z "${CURL_CMD}" ] ; then
+  CURL_CMD=curl
+fi
+
+# Explicit commandline argument takes precedence over all other methods
+if [ "$1" = "--mill-version" ] ; then
+  shift
+  if [ "x$1" != "x" ] ; then
+    MILL_VERSION="$1"
+    shift
+  else
+    echo "You specified --mill-version without a version." 1>&2
+    echo "Please provide a version that matches one provided on" 1>&2
+    echo "${MILL_REPO_URL}/releases" 1>&2
+    false
+  fi
+fi
+
+# Please note, that if a MILL_VERSION is already set in the environment,
+# We reuse it's value and skip searching for a value.
+
+# If not already set, read .mill-version file
+if [ -z "${MILL_VERSION}" ] ; then
+  if [ -f ".mill-version" ] ; then
+    MILL_VERSION="$(tr '\r' '\n' < .mill-version | head -n 1 2> /dev/null)"
+  elif [ -f ".config/mill-version" ] ; then
+    MILL_VERSION="$(tr '\r' '\n' < .config/mill-version | head -n 1 2> /dev/null)"
+  fi
+fi
+
+MILL_USER_CACHE_DIR="${XDG_CACHE_HOME:-${HOME}/.cache}/mill"
+
+if [ -z "${MILL_DOWNLOAD_PATH}" ] ; then
+  MILL_DOWNLOAD_PATH="${MILL_USER_CACHE_DIR}/download"
+fi
+
+# If not already set, try to fetch newest from Github
+if [ -z "${MILL_VERSION}" ] ; then
+  # TODO: try to load latest version from release page
+  echo "No mill version specified." 1>&2
+  echo "You should provide a version via '.mill-version' file or --mill-version option." 1>&2
+
+  mkdir -p "${MILL_DOWNLOAD_PATH}"
+  LANG=C touch -d '1 hour ago' "${MILL_DOWNLOAD_PATH}/.expire_latest" 2>/dev/null || (
+    # we might be on OSX or BSD which don't have -d option for touch
+    # but probably a -A [-][[hh]mm]SS
+    touch "${MILL_DOWNLOAD_PATH}/.expire_latest"; touch -A -010000 "${MILL_DOWNLOAD_PATH}/.expire_latest"
+  ) || (
+    # in case we still failed, we retry the first touch command with the intention
+    # to show the (previously suppressed) error message
+    LANG=C touch -d '1 hour ago' "${MILL_DOWNLOAD_PATH}/.expire_latest"
+  )
+
+  # POSIX shell variant of bash's -nt operator, see https://unix.stackexchange.com/a/449744/6993
+  # if [ "${MILL_DOWNLOAD_PATH}/.latest" -nt "${MILL_DOWNLOAD_PATH}/.expire_latest" ] ; then
+  if [ -n "$(find -L "${MILL_DOWNLOAD_PATH}/.latest" -prune -newer "${MILL_DOWNLOAD_PATH}/.expire_latest")" ]; then
+    # we know a current latest version
+    MILL_VERSION=$(head -n 1 "${MILL_DOWNLOAD_PATH}"/.latest 2> /dev/null)
+  fi
+
+  if [ -z "${MILL_VERSION}" ] ; then
+    # we don't know a current latest version
+    echo "Retrieving latest mill version ..." 1>&2
+    LANG=C ${CURL_CMD} -s -i -f -I ${MILL_REPO_URL}/releases/latest 2> /dev/null  | grep --ignore-case Location: | sed s'/^.*tag\///' | tr -d '\r\n' > "${MILL_DOWNLOAD_PATH}/.latest"
+    MILL_VERSION=$(head -n 1 "${MILL_DOWNLOAD_PATH}"/.latest 2> /dev/null)
+  fi
+
+  if [ -z "${MILL_VERSION}" ] ; then
+    # Last resort
+    MILL_VERSION="${DEFAULT_MILL_VERSION}"
+    echo "Falling back to hardcoded mill version ${MILL_VERSION}" 1>&2
+  else
+    echo "Using mill version ${MILL_VERSION}" 1>&2
+  fi
+fi
+
+MILL="${MILL_DOWNLOAD_PATH}/${MILL_VERSION}"
+
+try_to_use_system_mill() {
+  if [ "$(uname)" != "Linux" ]; then
+    return 0
+  fi
+
+  MILL_IN_PATH="$(command -v mill || true)"
+
+  if [ -z "${MILL_IN_PATH}" ]; then
+    return 0
+  fi
+
+  SYSTEM_MILL_FIRST_TWO_BYTES=$(head --bytes=2 "${MILL_IN_PATH}")
+  if [ "${SYSTEM_MILL_FIRST_TWO_BYTES}" = "#!" ]; then
+	  # MILL_IN_PATH is (very likely) a shell script and not the mill
+	  # executable, ignore it.
+	  return 0
+  fi
+
+  SYSTEM_MILL_PATH=$(readlink -e "${MILL_IN_PATH}")
+  SYSTEM_MILL_SIZE=$(stat --format=%s "${SYSTEM_MILL_PATH}")
+  SYSTEM_MILL_MTIME=$(stat --format=%y "${SYSTEM_MILL_PATH}")
+
+  if [ ! -d "${MILL_USER_CACHE_DIR}" ]; then
+    mkdir -p "${MILL_USER_CACHE_DIR}"
+  fi
+
+  SYSTEM_MILL_INFO_FILE="${MILL_USER_CACHE_DIR}/system-mill-info"
+  if [ -f "${SYSTEM_MILL_INFO_FILE}" ]; then
+    parseSystemMillInfo() {
+        LINE_NUMBER="${1}"
+        # Select the line number of the SYSTEM_MILL_INFO_FILE, cut the
+        # variable definition in that line in two halves and return
+        # the value, and finally remove the quotes.
+        sed -n "${LINE_NUMBER}p" "${SYSTEM_MILL_INFO_FILE}" |\
+            cut -d= -f2 |\
+            sed 's/"\(.*\)"/\1/'
+    }
+
+    CACHED_SYSTEM_MILL_PATH=$(parseSystemMillInfo 1)
+    CACHED_SYSTEM_MILL_VERSION=$(parseSystemMillInfo 2)
+    CACHED_SYSTEM_MILL_SIZE=$(parseSystemMillInfo 3)
+    CACHED_SYSTEM_MILL_MTIME=$(parseSystemMillInfo 4)
+
+    if [ "${SYSTEM_MILL_PATH}" = "${CACHED_SYSTEM_MILL_PATH}" ] \
+           && [ "${SYSTEM_MILL_SIZE}" = "${CACHED_SYSTEM_MILL_SIZE}" ] \
+           && [ "${SYSTEM_MILL_MTIME}" = "${CACHED_SYSTEM_MILL_MTIME}" ]; then
+      if [ "${CACHED_SYSTEM_MILL_VERSION}" = "${MILL_VERSION}" ]; then
+          MILL="${SYSTEM_MILL_PATH}"
+          return 0
+      else
+          return 0
+      fi
+    fi
+  fi
+
+  SYSTEM_MILL_VERSION=$(${SYSTEM_MILL_PATH} --version | head -n1 | sed -n 's/^Mill.*version \(.*\)/\1/p')
+
+  cat <<EOF > "${SYSTEM_MILL_INFO_FILE}"
+CACHED_SYSTEM_MILL_PATH="${SYSTEM_MILL_PATH}"
+CACHED_SYSTEM_MILL_VERSION="${SYSTEM_MILL_VERSION}"
+CACHED_SYSTEM_MILL_SIZE="${SYSTEM_MILL_SIZE}"
+CACHED_SYSTEM_MILL_MTIME="${SYSTEM_MILL_MTIME}"
+EOF
+
+  if [ "${SYSTEM_MILL_VERSION}" = "${MILL_VERSION}" ]; then
+    MILL="${SYSTEM_MILL_PATH}"
+  fi
+}
+try_to_use_system_mill
+
+# If not already downloaded, download it
+if [ ! -s "${MILL}" ] ; then
+
+  # support old non-XDG download dir
+  MILL_OLD_DOWNLOAD_PATH="${HOME}/.mill/download"
+  OLD_MILL="${MILL_OLD_DOWNLOAD_PATH}/${MILL_VERSION}"
+  if [ -x "${OLD_MILL}" ] ; then
+    MILL="${OLD_MILL}"
+  else
+    case $MILL_VERSION in
+      0.0.* | 0.1.* | 0.2.* | 0.3.* | 0.4.* )
+        DOWNLOAD_SUFFIX=""
+        DOWNLOAD_FROM_MAVEN=0
+        ;;
+      0.5.* | 0.6.* | 0.7.* | 0.8.* | 0.9.* | 0.10.* | 0.11.0-M* )
+        DOWNLOAD_SUFFIX="-assembly"
+        DOWNLOAD_FROM_MAVEN=0
+        ;;
+      *)
+        DOWNLOAD_SUFFIX="-assembly"
+        DOWNLOAD_FROM_MAVEN=1
+        ;;
+    esac
+
+    DOWNLOAD_FILE=$(mktemp mill.XXXXXX)
+
+    if [ "$DOWNLOAD_FROM_MAVEN" = "1" ] ; then
+      DOWNLOAD_URL="https://repo1.maven.org/maven2/com/lihaoyi/mill-dist/${MILL_VERSION}/mill-dist-${MILL_VERSION}.jar"
+    else
+      MILL_VERSION_TAG=$(echo "$MILL_VERSION" | sed -E 's/([^-]+)(-M[0-9]+)?(-.*)?/\1\2/')
+      DOWNLOAD_URL="${GITHUB_RELEASE_CDN}${MILL_REPO_URL}/releases/download/${MILL_VERSION_TAG}/${MILL_VERSION}${DOWNLOAD_SUFFIX}"
+      unset MILL_VERSION_TAG
+    fi
+
+    # TODO: handle command not found
+    echo "Downloading mill ${MILL_VERSION} from ${DOWNLOAD_URL} ..." 1>&2
+    ${CURL_CMD} -f -L -o "${DOWNLOAD_FILE}" "${DOWNLOAD_URL}"
+    chmod +x "${DOWNLOAD_FILE}"
+    mkdir -p "${MILL_DOWNLOAD_PATH}"
+    mv "${DOWNLOAD_FILE}" "${MILL}"
+
+    unset DOWNLOAD_FILE
+    unset DOWNLOAD_SUFFIX
+  fi
+fi
+
+if [ -z "$MILL_MAIN_CLI" ] ; then
+  MILL_MAIN_CLI="${0}"
+fi
+
+MILL_FIRST_ARG=""
+if [ "$1" = "--bsp" ] || [ "$1" = "-i" ] || [ "$1" = "--interactive" ] || [ "$1" = "--no-server" ] || [ "$1" = "--repl" ] || [ "$1" = "--help" ] ; then
+  # Need to preserve the first position of those listed options
+  MILL_FIRST_ARG=$1
+  shift
+fi
+
+unset MILL_DOWNLOAD_PATH
+unset MILL_OLD_DOWNLOAD_PATH
+unset OLD_MILL
+unset MILL_VERSION
+unset MILL_REPO_URL
+
+# We don't quote MILL_FIRST_ARG on purpose, so we can expand the empty value without quotes
+# shellcheck disable=SC2086
+exec "${MILL}" $MILL_FIRST_ARG -D "mill.main.cli=${MILL_MAIN_CLI}" "$@"
\ No newline at end of file
diff --git a/src/main/scala/arithmetic/P31.scala b/problems/arithmetic/src/P31.scala
similarity index 100%
rename from src/main/scala/arithmetic/P31.scala
rename to problems/arithmetic/src/P31.scala
diff --git a/src/main/scala/arithmetic/P32.scala b/problems/arithmetic/src/P32.scala
similarity index 100%
rename from src/main/scala/arithmetic/P32.scala
rename to problems/arithmetic/src/P32.scala
diff --git a/src/main/scala/arithmetic/P33.scala b/problems/arithmetic/src/P33.scala
similarity index 100%
rename from src/main/scala/arithmetic/P33.scala
rename to problems/arithmetic/src/P33.scala
diff --git a/src/main/scala/arithmetic/P34.scala b/problems/arithmetic/src/P34.scala
similarity index 100%
rename from src/main/scala/arithmetic/P34.scala
rename to problems/arithmetic/src/P34.scala
diff --git a/src/main/scala/arithmetic/P35.scala b/problems/arithmetic/src/P35.scala
similarity index 100%
rename from src/main/scala/arithmetic/P35.scala
rename to problems/arithmetic/src/P35.scala
diff --git a/src/main/scala/arithmetic/P36.scala b/problems/arithmetic/src/P36.scala
similarity index 100%
rename from src/main/scala/arithmetic/P36.scala
rename to problems/arithmetic/src/P36.scala
diff --git a/src/main/scala/arithmetic/P39.scala b/problems/arithmetic/src/P39.scala
similarity index 100%
rename from src/main/scala/arithmetic/P39.scala
rename to problems/arithmetic/src/P39.scala
diff --git a/src/main/scala/arithmetic/P40.scala b/problems/arithmetic/src/P40.scala
similarity index 100%
rename from src/main/scala/arithmetic/P40.scala
rename to problems/arithmetic/src/P40.scala
diff --git a/src/main/scala/arithmetic/P41.scala b/problems/arithmetic/src/P41.scala
similarity index 100%
rename from src/main/scala/arithmetic/P41.scala
rename to problems/arithmetic/src/P41.scala
diff --git a/src/test/scala/arithmetic/P31Suite.scala b/problems/arithmetic/test/src/P31Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P31Suite.scala
rename to problems/arithmetic/test/src/P31Suite.scala
diff --git a/src/test/scala/arithmetic/P32Suite.scala b/problems/arithmetic/test/src/P32Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P32Suite.scala
rename to problems/arithmetic/test/src/P32Suite.scala
diff --git a/src/test/scala/arithmetic/P33Suite.scala b/problems/arithmetic/test/src/P33Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P33Suite.scala
rename to problems/arithmetic/test/src/P33Suite.scala
diff --git a/src/test/scala/arithmetic/P34Suite.scala b/problems/arithmetic/test/src/P34Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P34Suite.scala
rename to problems/arithmetic/test/src/P34Suite.scala
diff --git a/src/test/scala/arithmetic/P35Suite.scala b/problems/arithmetic/test/src/P35Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P35Suite.scala
rename to problems/arithmetic/test/src/P35Suite.scala
diff --git a/src/test/scala/arithmetic/P36Suite.scala b/problems/arithmetic/test/src/P36Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P36Suite.scala
rename to problems/arithmetic/test/src/P36Suite.scala
diff --git a/src/test/scala/arithmetic/P39Suite.scala b/problems/arithmetic/test/src/P39Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P39Suite.scala
rename to problems/arithmetic/test/src/P39Suite.scala
diff --git a/src/test/scala/arithmetic/P40Suite.scala b/problems/arithmetic/test/src/P40Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P40Suite.scala
rename to problems/arithmetic/test/src/P40Suite.scala
diff --git a/src/test/scala/arithmetic/P41Suite.scala b/problems/arithmetic/test/src/P41Suite.scala
similarity index 100%
rename from src/test/scala/arithmetic/P41Suite.scala
rename to problems/arithmetic/test/src/P41Suite.scala
diff --git a/src/main/scala/bintree/P55.scala b/problems/bintree/src/P55.scala
similarity index 100%
rename from src/main/scala/bintree/P55.scala
rename to problems/bintree/src/P55.scala
diff --git a/src/main/scala/bintree/P56.scala b/problems/bintree/src/P56.scala
similarity index 100%
rename from src/main/scala/bintree/P56.scala
rename to problems/bintree/src/P56.scala
diff --git a/src/main/scala/bintree/P57.scala b/problems/bintree/src/P57.scala
similarity index 100%
rename from src/main/scala/bintree/P57.scala
rename to problems/bintree/src/P57.scala
diff --git a/src/main/scala/bintree/P58.scala b/problems/bintree/src/P58.scala
similarity index 100%
rename from src/main/scala/bintree/P58.scala
rename to problems/bintree/src/P58.scala
diff --git a/src/main/scala/bintree/P59.scala b/problems/bintree/src/P59.scala
similarity index 100%
rename from src/main/scala/bintree/P59.scala
rename to problems/bintree/src/P59.scala
diff --git a/src/main/scala/bintree/Tree.scala b/problems/bintree/src/Tree.scala
similarity index 100%
rename from src/main/scala/bintree/Tree.scala
rename to problems/bintree/src/Tree.scala
diff --git a/src/test/scala/bintree/P55Suite.scala b/problems/bintree/test/src/P55Suite.scala
similarity index 100%
rename from src/test/scala/bintree/P55Suite.scala
rename to problems/bintree/test/src/P55Suite.scala
diff --git a/src/test/scala/bintree/P56Suite.scala b/problems/bintree/test/src/P56Suite.scala
similarity index 100%
rename from src/test/scala/bintree/P56Suite.scala
rename to problems/bintree/test/src/P56Suite.scala
diff --git a/src/test/scala/bintree/P57Suite.scala b/problems/bintree/test/src/P57Suite.scala
similarity index 97%
rename from src/test/scala/bintree/P57Suite.scala
rename to problems/bintree/test/src/P57Suite.scala
index b717403..cc5deef 100644
--- a/src/test/scala/bintree/P57Suite.scala
+++ b/problems/bintree/test/src/P57Suite.scala
@@ -1,7 +1,6 @@
 package bintree
 
 import munit.FunSuite
-import Tree.*
 import P56.*
 import P57.*
 
diff --git a/src/test/scala/bintree/P58Suite.scala b/problems/bintree/test/src/P58Suite.scala
similarity index 100%
rename from src/test/scala/bintree/P58Suite.scala
rename to problems/bintree/test/src/P58Suite.scala
diff --git a/src/test/scala/bintree/P59Suite.scala b/problems/bintree/test/src/P59Suite.scala
similarity index 100%
rename from src/test/scala/bintree/P59Suite.scala
rename to problems/bintree/test/src/P59Suite.scala
diff --git a/src/main/scala/list/P01.scala b/problems/list/src/P01.scala
similarity index 100%
rename from src/main/scala/list/P01.scala
rename to problems/list/src/P01.scala
diff --git a/src/main/scala/list/P02.scala b/problems/list/src/P02.scala
similarity index 100%
rename from src/main/scala/list/P02.scala
rename to problems/list/src/P02.scala
diff --git a/src/main/scala/list/P03.scala b/problems/list/src/P03.scala
similarity index 100%
rename from src/main/scala/list/P03.scala
rename to problems/list/src/P03.scala
diff --git a/src/main/scala/list/P04.scala b/problems/list/src/P04.scala
similarity index 100%
rename from src/main/scala/list/P04.scala
rename to problems/list/src/P04.scala
diff --git a/src/main/scala/list/P05.scala b/problems/list/src/P05.scala
similarity index 100%
rename from src/main/scala/list/P05.scala
rename to problems/list/src/P05.scala
diff --git a/src/main/scala/list/P06.scala b/problems/list/src/P06.scala
similarity index 100%
rename from src/main/scala/list/P06.scala
rename to problems/list/src/P06.scala
diff --git a/src/main/scala/list/P07.scala b/problems/list/src/P07.scala
similarity index 100%
rename from src/main/scala/list/P07.scala
rename to problems/list/src/P07.scala
diff --git a/src/main/scala/list/P08.scala b/problems/list/src/P08.scala
similarity index 100%
rename from src/main/scala/list/P08.scala
rename to problems/list/src/P08.scala
diff --git a/src/main/scala/list/P09.scala b/problems/list/src/P09.scala
similarity index 100%
rename from src/main/scala/list/P09.scala
rename to problems/list/src/P09.scala
diff --git a/src/main/scala/list/P10.scala b/problems/list/src/P10.scala
similarity index 100%
rename from src/main/scala/list/P10.scala
rename to problems/list/src/P10.scala
diff --git a/src/main/scala/list/P11.scala b/problems/list/src/P11.scala
similarity index 100%
rename from src/main/scala/list/P11.scala
rename to problems/list/src/P11.scala
diff --git a/src/main/scala/list/P12.scala b/problems/list/src/P12.scala
similarity index 100%
rename from src/main/scala/list/P12.scala
rename to problems/list/src/P12.scala
diff --git a/src/main/scala/list/P13.scala b/problems/list/src/P13.scala
similarity index 100%
rename from src/main/scala/list/P13.scala
rename to problems/list/src/P13.scala
diff --git a/src/main/scala/list/P14.scala b/problems/list/src/P14.scala
similarity index 100%
rename from src/main/scala/list/P14.scala
rename to problems/list/src/P14.scala
diff --git a/src/main/scala/list/P15.scala b/problems/list/src/P15.scala
similarity index 100%
rename from src/main/scala/list/P15.scala
rename to problems/list/src/P15.scala
diff --git a/src/main/scala/list/P16.scala b/problems/list/src/P16.scala
similarity index 100%
rename from src/main/scala/list/P16.scala
rename to problems/list/src/P16.scala
diff --git a/src/main/scala/list/P17.scala b/problems/list/src/P17.scala
similarity index 100%
rename from src/main/scala/list/P17.scala
rename to problems/list/src/P17.scala
diff --git a/src/main/scala/list/P18.scala b/problems/list/src/P18.scala
similarity index 100%
rename from src/main/scala/list/P18.scala
rename to problems/list/src/P18.scala
diff --git a/src/main/scala/list/P19.scala b/problems/list/src/P19.scala
similarity index 100%
rename from src/main/scala/list/P19.scala
rename to problems/list/src/P19.scala
diff --git a/src/main/scala/list/P20.scala b/problems/list/src/P20.scala
similarity index 100%
rename from src/main/scala/list/P20.scala
rename to problems/list/src/P20.scala
diff --git a/src/main/scala/list/P21.scala b/problems/list/src/P21.scala
similarity index 100%
rename from src/main/scala/list/P21.scala
rename to problems/list/src/P21.scala
diff --git a/src/main/scala/list/P22.scala b/problems/list/src/P22.scala
similarity index 100%
rename from src/main/scala/list/P22.scala
rename to problems/list/src/P22.scala
diff --git a/src/main/scala/list/P23.scala b/problems/list/src/P23.scala
similarity index 100%
rename from src/main/scala/list/P23.scala
rename to problems/list/src/P23.scala
diff --git a/src/main/scala/list/P24.scala b/problems/list/src/P24.scala
similarity index 100%
rename from src/main/scala/list/P24.scala
rename to problems/list/src/P24.scala
diff --git a/src/main/scala/list/P25.scala b/problems/list/src/P25.scala
similarity index 100%
rename from src/main/scala/list/P25.scala
rename to problems/list/src/P25.scala
diff --git a/src/main/scala/list/P26.scala b/problems/list/src/P26.scala
similarity index 100%
rename from src/main/scala/list/P26.scala
rename to problems/list/src/P26.scala
diff --git a/src/main/scala/list/P27.scala b/problems/list/src/P27.scala
similarity index 100%
rename from src/main/scala/list/P27.scala
rename to problems/list/src/P27.scala
diff --git a/src/main/scala/list/P28.scala b/problems/list/src/P28.scala
similarity index 100%
rename from src/main/scala/list/P28.scala
rename to problems/list/src/P28.scala
diff --git a/src/test/scala/list/ListGen.scala b/problems/list/test/src/ListGen.scala
similarity index 100%
rename from src/test/scala/list/ListGen.scala
rename to problems/list/test/src/ListGen.scala
diff --git a/src/test/scala/list/P01Suite.scala b/problems/list/test/src/P01Suite.scala
similarity index 100%
rename from src/test/scala/list/P01Suite.scala
rename to problems/list/test/src/P01Suite.scala
diff --git a/src/test/scala/list/P02Suite.scala b/problems/list/test/src/P02Suite.scala
similarity index 100%
rename from src/test/scala/list/P02Suite.scala
rename to problems/list/test/src/P02Suite.scala
diff --git a/src/test/scala/list/P03Suite.scala b/problems/list/test/src/P03Suite.scala
similarity index 100%
rename from src/test/scala/list/P03Suite.scala
rename to problems/list/test/src/P03Suite.scala
diff --git a/src/test/scala/list/P04Suite.scala b/problems/list/test/src/P04Suite.scala
similarity index 100%
rename from src/test/scala/list/P04Suite.scala
rename to problems/list/test/src/P04Suite.scala
diff --git a/src/test/scala/list/P05Suite.scala b/problems/list/test/src/P05Suite.scala
similarity index 100%
rename from src/test/scala/list/P05Suite.scala
rename to problems/list/test/src/P05Suite.scala
diff --git a/src/test/scala/list/P06Suite.scala b/problems/list/test/src/P06Suite.scala
similarity index 100%
rename from src/test/scala/list/P06Suite.scala
rename to problems/list/test/src/P06Suite.scala
diff --git a/src/test/scala/list/P07Suite.scala b/problems/list/test/src/P07Suite.scala
similarity index 100%
rename from src/test/scala/list/P07Suite.scala
rename to problems/list/test/src/P07Suite.scala
diff --git a/src/test/scala/list/P08Suite.scala b/problems/list/test/src/P08Suite.scala
similarity index 100%
rename from src/test/scala/list/P08Suite.scala
rename to problems/list/test/src/P08Suite.scala
diff --git a/src/test/scala/list/P09Suite.scala b/problems/list/test/src/P09Suite.scala
similarity index 100%
rename from src/test/scala/list/P09Suite.scala
rename to problems/list/test/src/P09Suite.scala
diff --git a/src/test/scala/list/P10Suite.scala b/problems/list/test/src/P10Suite.scala
similarity index 100%
rename from src/test/scala/list/P10Suite.scala
rename to problems/list/test/src/P10Suite.scala
diff --git a/src/test/scala/list/P11Suite.scala b/problems/list/test/src/P11Suite.scala
similarity index 100%
rename from src/test/scala/list/P11Suite.scala
rename to problems/list/test/src/P11Suite.scala
diff --git a/src/test/scala/list/P12Suite.scala b/problems/list/test/src/P12Suite.scala
similarity index 100%
rename from src/test/scala/list/P12Suite.scala
rename to problems/list/test/src/P12Suite.scala
diff --git a/src/test/scala/list/P13Suite.scala b/problems/list/test/src/P13Suite.scala
similarity index 100%
rename from src/test/scala/list/P13Suite.scala
rename to problems/list/test/src/P13Suite.scala
diff --git a/src/test/scala/list/P14Suite.scala b/problems/list/test/src/P14Suite.scala
similarity index 100%
rename from src/test/scala/list/P14Suite.scala
rename to problems/list/test/src/P14Suite.scala
diff --git a/src/test/scala/list/P15Suite.scala b/problems/list/test/src/P15Suite.scala
similarity index 100%
rename from src/test/scala/list/P15Suite.scala
rename to problems/list/test/src/P15Suite.scala
diff --git a/src/test/scala/list/P16Suite.scala b/problems/list/test/src/P16Suite.scala
similarity index 100%
rename from src/test/scala/list/P16Suite.scala
rename to problems/list/test/src/P16Suite.scala
diff --git a/src/test/scala/list/P17Suite.scala b/problems/list/test/src/P17Suite.scala
similarity index 100%
rename from src/test/scala/list/P17Suite.scala
rename to problems/list/test/src/P17Suite.scala
diff --git a/src/test/scala/list/P18Suite.scala b/problems/list/test/src/P18Suite.scala
similarity index 100%
rename from src/test/scala/list/P18Suite.scala
rename to problems/list/test/src/P18Suite.scala
diff --git a/src/test/scala/list/P19Suite.scala b/problems/list/test/src/P19Suite.scala
similarity index 100%
rename from src/test/scala/list/P19Suite.scala
rename to problems/list/test/src/P19Suite.scala
diff --git a/src/test/scala/list/P20Suite.scala b/problems/list/test/src/P20Suite.scala
similarity index 100%
rename from src/test/scala/list/P20Suite.scala
rename to problems/list/test/src/P20Suite.scala
diff --git a/src/test/scala/list/P21Suite.scala b/problems/list/test/src/P21Suite.scala
similarity index 100%
rename from src/test/scala/list/P21Suite.scala
rename to problems/list/test/src/P21Suite.scala
diff --git a/src/test/scala/list/P22Suite.scala b/problems/list/test/src/P22Suite.scala
similarity index 100%
rename from src/test/scala/list/P22Suite.scala
rename to problems/list/test/src/P22Suite.scala
diff --git a/src/test/scala/list/P23Suite.scala b/problems/list/test/src/P23Suite.scala
similarity index 100%
rename from src/test/scala/list/P23Suite.scala
rename to problems/list/test/src/P23Suite.scala
diff --git a/src/test/scala/list/P24Suite.scala b/problems/list/test/src/P24Suite.scala
similarity index 100%
rename from src/test/scala/list/P24Suite.scala
rename to problems/list/test/src/P24Suite.scala
diff --git a/src/test/scala/list/P25Suite.scala b/problems/list/test/src/P25Suite.scala
similarity index 100%
rename from src/test/scala/list/P25Suite.scala
rename to problems/list/test/src/P25Suite.scala
diff --git a/src/test/scala/list/P26Suite.scala b/problems/list/test/src/P26Suite.scala
similarity index 100%
rename from src/test/scala/list/P26Suite.scala
rename to problems/list/test/src/P26Suite.scala
diff --git a/src/test/scala/list/P27Suite.scala b/problems/list/test/src/P27Suite.scala
similarity index 100%
rename from src/test/scala/list/P27Suite.scala
rename to problems/list/test/src/P27Suite.scala
diff --git a/src/test/scala/list/P28Suite.scala b/problems/list/test/src/P28Suite.scala
similarity index 100%
rename from src/test/scala/list/P28Suite.scala
rename to problems/list/test/src/P28Suite.scala
diff --git a/src/main/scala/logic/P46.scala b/problems/logic/src/P46.scala
similarity index 100%
rename from src/main/scala/logic/P46.scala
rename to problems/logic/src/P46.scala
diff --git a/src/main/scala/logic/P47.scala b/problems/logic/src/P47.scala
similarity index 100%
rename from src/main/scala/logic/P47.scala
rename to problems/logic/src/P47.scala
diff --git a/src/main/scala/logic/P49.scala b/problems/logic/src/P49.scala
similarity index 100%
rename from src/main/scala/logic/P49.scala
rename to problems/logic/src/P49.scala
diff --git a/src/main/scala/logic/P50.scala b/problems/logic/src/P50.scala
similarity index 100%
rename from src/main/scala/logic/P50.scala
rename to problems/logic/src/P50.scala
diff --git a/src/test/scala/logic/P46Suite.scala b/problems/logic/test/src/P46Suite.scala
similarity index 100%
rename from src/test/scala/logic/P46Suite.scala
rename to problems/logic/test/src/P46Suite.scala
diff --git a/src/test/scala/logic/P47Suite.scala b/problems/logic/test/src/P47Suite.scala
similarity index 100%
rename from src/test/scala/logic/P47Suite.scala
rename to problems/logic/test/src/P47Suite.scala
diff --git a/src/test/scala/logic/P49Spec.scala b/problems/logic/test/src/P49Spec.scala
similarity index 100%
rename from src/test/scala/logic/P49Spec.scala
rename to problems/logic/test/src/P49Spec.scala
diff --git a/src/test/scala/logic/P50Spec.scala b/problems/logic/test/src/P50Spec.scala
similarity index 100%
rename from src/test/scala/logic/P50Spec.scala
rename to problems/logic/test/src/P50Spec.scala
diff --git a/project/build.properties b/project/build.properties
deleted file mode 100644
index e8a1e24..0000000
--- a/project/build.properties
+++ /dev/null
@@ -1 +0,0 @@
-sbt.version=1.9.7
diff --git a/project/plugins.sbt b/project/plugins.sbt
deleted file mode 100644
index f02b4bb..0000000
--- a/project/plugins.sbt
+++ /dev/null
@@ -1 +0,0 @@
-addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.4.6")
\ No newline at end of file
diff --git a/versions.mill b/versions.mill
new file mode 100644
index 0000000..52199fd
--- /dev/null
+++ b/versions.mill
@@ -0,0 +1,5 @@
+package build
+
+val scalaVersion = "3.6.2"
+val munitVersion = "1.0.3"
+val munitScalaCheckVersion = "1.0.0"
\ No newline at end of file