diff --git a/README.md b/README.md
index fcf3f057..035f869d 100644
--- a/README.md
+++ b/README.md
@@ -5,3 +5,8 @@
 
 ## 과제 제출 과정
 * [과제 제출 방법](https://github.com/next-step/nextstep-docs/tree/master/ent-precourse)
+
+## 구현 기능
+- 임의의 3자리 수 선정
+- 유저 input & 결과(힌트) return
+- (게임 오버 시) 재시작 여부 체크
diff --git a/src/main/java/Application.java b/src/main/java/Application.java
new file mode 100644
index 00000000..da7e3469
--- /dev/null
+++ b/src/main/java/Application.java
@@ -0,0 +1,13 @@
+import game.BaseballGame;
+import service.RandomGenerator;
+
+public class Application {
+    public static void main(String[] args) {
+        RandomGenerator.generateRandomNumber();
+        Boolean keepPlaying = true;
+        while (keepPlaying) {
+            BaseballGame baseballGame = new BaseballGame();
+            keepPlaying = baseballGame.playGame();
+        }
+    }
+}
diff --git a/src/main/java/game/BaseballGame.java b/src/main/java/game/BaseballGame.java
new file mode 100644
index 00000000..4cf239f2
--- /dev/null
+++ b/src/main/java/game/BaseballGame.java
@@ -0,0 +1,66 @@
+package game;
+
+import service.RandomGenerator;
+import service.StrikeBallCount;
+import service.SubmissionValidator;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Scanner;
+
+public class BaseballGame {
+    private final List<Integer> answer;
+    private final List<Integer> userInput = new ArrayList<>();
+    private final Scanner scanner = new Scanner(System.in);
+
+    public BaseballGame() {
+        this.answer = RandomGenerator.generateRandomNumber();
+    }
+
+    public Boolean playGame() {
+        Boolean stop = false;
+        while (!stop) {
+            stop = progressGame();
+        }
+        System.out.println("3개의 숫자를 모두 맞히셨습니다! 게임 종료");
+        System.out.println("게임을 새로 시작하려면 1, 종료하려면 2를 입력하세요.");
+        return scanner.nextInt() == 1;
+    }
+
+    private Boolean progressGame() {
+        setUserInput();
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(userInput, answer);
+        System.out.println(strikeBallCount.getResultString());
+        return strikeBallCount.isCorrect();
+    }
+
+    private void setUserInput() {
+        System.out.print("숫자를 입력해주세요: ");
+        String input = scanner.nextLine().replaceAll("\\s", "");
+        if (isInputValid(input)) {
+            updateUserInput(input);
+            return;
+        }
+        System.out.println("올바른 숫자를 입력해 주세요!");
+        setUserInput();
+    }
+
+    private void updateUserInput(String input) {
+        userInput.clear();
+        for (int i = 0; i < 3; i++) {
+            userInput.add(Character.getNumericValue(input.charAt(i)));
+        }
+    }
+
+    private boolean isInputValid(String input) {
+        if (input.length() != 3) return false;
+        int idx = 0;
+        while (idx < 3 && Character.isDigit(input.charAt(idx)) && Character.getNumericValue(input.charAt(idx)) > 0) {
+            idx++;
+        }
+        if (idx != 3) {
+            return false;
+        }
+        return true;
+    }
+}
diff --git a/src/main/java/service/RandomGenerator.java b/src/main/java/service/RandomGenerator.java
new file mode 100644
index 00000000..78c900ee
--- /dev/null
+++ b/src/main/java/service/RandomGenerator.java
@@ -0,0 +1,22 @@
+package service;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class RandomGenerator {
+    public static List<Integer> generateRandomNumber() {
+        ArrayList<Integer> candidate = new ArrayList<>();
+        while (candidate.size() < 3) {
+            insertDistinctNumber(candidate);
+        }
+        return candidate;
+    }
+
+    private static void insertDistinctNumber(List<Integer> candidate) {
+        int newCandidate = (int) ((Math.random() * 8) + 1);
+        while (candidate.contains(newCandidate)) {
+            newCandidate = (int) ((Math.random() * 8) + 1);
+        }
+        candidate.add(newCandidate);
+    }
+}
diff --git a/src/main/java/service/StrikeBallCount.java b/src/main/java/service/StrikeBallCount.java
new file mode 100644
index 00000000..39a6bb2e
--- /dev/null
+++ b/src/main/java/service/StrikeBallCount.java
@@ -0,0 +1,38 @@
+package service;
+
+public class StrikeBallCount {
+    private int strikeCount = 0;
+    private int ballCount = 0;
+
+    public int getStrikeCount() {
+        return strikeCount;
+    }
+
+    public int getBallCount() {
+        return ballCount;
+    }
+
+    public void updateStrike() {
+        this.strikeCount += 1;
+    }
+
+    public void updateBall() {
+        this.ballCount += 1;
+    }
+
+    public Boolean isCorrect() {
+        return this.strikeCount == 3;
+    }
+
+    public Boolean isNothing() {
+        return this.ballCount == 0 & this.strikeCount == 0;
+    }
+
+    public String getResultString() {
+        StringBuilder res = new StringBuilder();
+        if (this.strikeCount > 0) res.append(strikeCount).append("스트라이크 ");
+        if (this.ballCount > 0) res.append(ballCount).append("볼");
+        if (this.isNothing()) res.append("낫싱");
+        return res.toString();
+    }
+}
diff --git a/src/main/java/service/SubmissionValidator.java b/src/main/java/service/SubmissionValidator.java
new file mode 100644
index 00000000..1a7157e0
--- /dev/null
+++ b/src/main/java/service/SubmissionValidator.java
@@ -0,0 +1,24 @@
+package service;
+
+import java.util.List;
+
+public class SubmissionValidator {
+    public static StrikeBallCount validateSubmission(List<Integer> submission, List<Integer> answer) {
+        StrikeBallCount strikeBallCount = new StrikeBallCount();
+        for (int idx = 0; idx < 3; idx++) {
+            updateStrikeBallCountPerIdx(idx, submission, answer, strikeBallCount);
+        }
+        return strikeBallCount;
+    }
+
+    private static void updateStrikeBallCountPerIdx(int idx, List<Integer> submission, List<Integer> answer, StrikeBallCount strikeBallCount) {
+        if (submission.get(idx).equals(answer.get(idx))) {
+            strikeBallCount.updateStrike();
+            return;
+        }
+        if(answer.contains(submission.get(idx))) {
+            strikeBallCount.updateBall();
+            return;
+        }
+    }
+}
diff --git a/src/test/java/game/BaseballGameTest.java b/src/test/java/game/BaseballGameTest.java
new file mode 100644
index 00000000..d2c3861d
--- /dev/null
+++ b/src/test/java/game/BaseballGameTest.java
@@ -0,0 +1,10 @@
+package game;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class BaseballGameTest {
+    BaseballGame game = new BaseballGame();
+
+}
\ No newline at end of file
diff --git a/src/test/java/service/RandomGeneratorTest.java b/src/test/java/service/RandomGeneratorTest.java
new file mode 100644
index 00000000..3431104f
--- /dev/null
+++ b/src/test/java/service/RandomGeneratorTest.java
@@ -0,0 +1,30 @@
+package service;
+
+import org.junit.jupiter.api.Test;
+import java.util.HashSet;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.*;
+
+class RandomGeneratorTest {
+
+    @Test
+    void generateRandomNumber_sizeIsThree() {
+        List<Integer> randomNumber = RandomGenerator.generateRandomNumber();
+        assertThat(randomNumber.size()).isEqualTo(3);
+    }
+
+    @Test
+    void generateRandomNumber_noDuplicate() {
+        List<Integer> randomNumber = RandomGenerator.generateRandomNumber();
+        assertThat(new HashSet<>(randomNumber).size()).isEqualTo(randomNumber.size());
+    }
+
+    @Test
+    void generateRandomNumber_isInRange() {
+        List<Integer> randomNumber = RandomGenerator.generateRandomNumber();
+        for (Integer num : randomNumber) {
+            assertThat(num).isBetween(1, 9);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/service/SubmissionValidatorTest.java b/src/test/java/service/SubmissionValidatorTest.java
new file mode 100644
index 00000000..5bd355d0
--- /dev/null
+++ b/src/test/java/service/SubmissionValidatorTest.java
@@ -0,0 +1,164 @@
+package service;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.*;
+
+class SubmissionValidatorTest {
+
+    @Test
+    void validateSubmission_isStrikeThree() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(1);
+        answer.add(2);
+        answer.add(3);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(3);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(0);
+    }
+
+    @Test
+    void validateSubmission_isStrikeThreeAndCorrect() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(1);
+        answer.add(2);
+        answer.add(3);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(3);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(0);
+        assertThat(strikeBallCount.isCorrect()).isTrue();
+    }
+
+    @Test
+    void validateSubmission_isBallThree() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(3);
+        answer.add(1);
+        answer.add(2);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(0);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(3);
+    }
+
+    @Test
+    void validateSubmission_isTwoBallOneStrike() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(1);
+        answer.add(3);
+        answer.add(2);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(1);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(2);
+    }
+
+    @Test
+    void validateSubmission_isOneBall() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(4);
+        answer.add(5);
+        answer.add(1);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(0);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(1);
+    }
+
+    @Test
+    void validateSubmission_noMatch() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(4);
+        answer.add(5);
+        answer.add(6);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(0);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(0);
+    }
+
+    @Test
+    void validateSubmission_noMatchAndNothing() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(4);
+        answer.add(5);
+        answer.add(6);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getStrikeCount()).isEqualTo(0);
+        assertThat(strikeBallCount.getBallCount()).isEqualTo(0);
+        assertThat(strikeBallCount.isNothing()).isTrue();
+    }
+
+    @Test
+    void validateSubmission_resultStringIsTwoBallOneStrike() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(1);
+        answer.add(3);
+        answer.add(2);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getResultString()).isEqualTo("1스트라이크 2볼");
+    }
+
+    @Test
+    void validateSubmission_resultStringIsNothing() {
+        List<Integer> submission = new ArrayList<>();
+        submission.add(1);
+        submission.add(2);
+        submission.add(3);
+
+        List<Integer> answer = new ArrayList<>();
+        answer.add(4);
+        answer.add(5);
+        answer.add(6);
+
+        StrikeBallCount strikeBallCount = SubmissionValidator.validateSubmission(submission, answer);
+        assertThat(strikeBallCount.getResultString()).isEqualTo("낫싱");
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/study/SetTest.java b/src/test/java/study/SetTest.java
new file mode 100644
index 00000000..5f833d7c
--- /dev/null
+++ b/src/test/java/study/SetTest.java
@@ -0,0 +1,43 @@
+package study;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SetTest {
+    private Set<Integer> numbers;
+
+    @BeforeEach
+    void setUp() {
+        numbers = new HashSet<>();
+        numbers.add(1);
+        numbers.add(1);
+        numbers.add(2);
+        numbers.add(3);
+    }
+
+    @Test
+    void sizeOfSet() {
+        assertThat(numbers.size()).isEqualTo(3);
+    }
+
+    @ParameterizedTest
+    @ValueSource(ints = {1, 2, 3})
+    void contains(int input) {
+        assertThat(numbers.contains(input)).isTrue();
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"1:true", "2:true", "3:true", "4:false", "5:false"}, delimiter = ':')
+    void contains_trueAndFalse(int input, Boolean expected) {
+        Assertions.assertEquals(expected, numbers.contains(input));
+    }
+}
diff --git a/src/test/java/study/StringTest.java b/src/test/java/study/StringTest.java
index 43e47d90..6447fb39 100644
--- a/src/test/java/study/StringTest.java
+++ b/src/test/java/study/StringTest.java
@@ -2,12 +2,35 @@
 
 import org.junit.jupiter.api.Test;
 
-import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.*;
 
 public class StringTest {
     @Test
-    void replace() {
-        String actual = "abc".replace("b", "d");
-        assertThat(actual).isEqualTo("adc");
+    void splitOneAndTwo() {
+        String str = "1,2";
+        String[] resStr = str.split(",");
+        assertThat(resStr).contains("1", "2");
+    }
+
+    @Test
+    void splitOne() {
+        String str = "1";
+        String[] resStr = str.split(",");
+        assertThat(resStr).containsExactly("1");
+    }
+
+    @Test
+    void removeParenthesis() {
+        String str = "(1,2)";
+        String resStr = str.substring(1, 4);
+        assertThat(resStr).isEqualTo("1,2");
+    }
+
+    @Test
+    void strIdxOutOfBound() {
+        String str = "abc";
+        assertThatExceptionOfType(IndexOutOfBoundsException.class).isThrownBy(() -> {
+            str.charAt(3);
+        }).withMessageMatching("Index \\d+ out of bounds for length \\d+");
     }
 }