diff --git a/.gitignore b/.gitignore
index 6c01878138..5dca701a77 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,6 @@ out/
 
 ### VS Code ###
 .vscode/
+
+### Mac OS ###
+.DS_Store
diff --git a/build.gradle.kts b/build.gradle.kts
index e78e729567..0191fcd943 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,28 +1,26 @@
 plugins {
-    kotlin("jvm") version "1.8.10"
-    id("org.jlleitschuh.gradle.ktlint") version "10.3.0"
+    kotlin("jvm") version "1.9.24"
+    id("org.jlleitschuh.gradle.ktlint") version "12.1.0"
 }
 
 group = "camp.nextstep.edu"
 version = "1.0-SNAPSHOT"
 
+kotlin {
+    jvmToolchain(21)
+}
+
 repositories {
     mavenCentral()
 }
 
 dependencies {
-    testImplementation("org.junit.jupiter", "junit-jupiter", "5.8.2")
-    testImplementation("org.assertj", "assertj-core", "3.22.0")
-    testImplementation("io.kotest", "kotest-runner-junit5", "5.2.3")
+    testImplementation("org.junit.jupiter", "junit-jupiter", "5.10.2")
+    testImplementation("org.assertj", "assertj-core", "3.25.3")
+    testImplementation("io.kotest", "kotest-runner-junit5", "5.8.0")
 }
 
 tasks {
-    compileKotlin {
-        kotlinOptions.jvmTarget = "11"
-    }
-    compileTestKotlin {
-        kotlinOptions.jvmTarget = "11"
-    }
     test {
         useJUnitPlatform()
     }
diff --git a/gradle.properties b/gradle.properties
index 29e08e8ca8..7fc6f1ff27 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1 +1 @@
-kotlin.code.style=official
\ No newline at end of file
+kotlin.code.style=official
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 943f0cbfa7..e6441136f3 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index f398c33c4b..b82aa23a4f 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.6-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
 networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 65dcd68d65..1aa94a4269 100755
--- a/gradlew
+++ b/gradlew
@@ -83,10 +83,8 @@ done
 # This is normally unused
 # shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -133,10 +131,13 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
@@ -144,7 +145,7 @@ if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
         # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
-        # shellcheck disable=SC3045 
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
@@ -152,7 +153,7 @@ if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
       '' | soft) :;; #(
       *)
         # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
-        # shellcheck disable=SC3045 
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -197,11 +198,15 @@ if "$cygwin" || "$msys" ; then
     done
 fi
 
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
diff --git a/gradlew.bat b/gradlew.bat
index 6689b85bee..7101f8e467 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -43,11 +43,11 @@ set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
 if %ERRORLEVEL% equ 0 goto execute
 
-echo.
-echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
 goto fail
 
@@ -57,11 +57,11 @@ set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
 if exist "%JAVA_EXE%" goto execute
 
-echo.
-echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
-echo.
-echo Please set the JAVA_HOME variable in your environment to match the
-echo location of your Java installation.
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
 
 goto fail
 
diff --git a/settings.gradle.kts b/settings.gradle.kts
index c926782029..ea3d11c28b 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -1 +1,4 @@
+plugins {
+    id("org.gradle.toolchains.foojay-resolver-convention") version "0.8.0"
+}
 rootProject.name = "kotlin-blackjack"