diff --git a/README.md b/README.md
index fcf3f057..89884fda 100644
--- a/README.md
+++ b/README.md
@@ -5,3 +5,15 @@
 
 ## 과제 제출 과정
 * [과제 제출 방법](https://github.com/next-step/nextstep-docs/tree/master/ent-precourse)
+
+
+## 기능 구현
+Main:
+BaseballGame:
+- startGame: 게임을 시작한다.
+- runGame: 게임의 전체 흐름을 순서대로 호출한다.
+- setGame: 컴퓨터의 정답을 정한다.
+- setUserAnswer: 유저의 정답을 입력받는다.
+- evaluate: 유저의 정답에 대해 스트라이크, 볼을 계산한다.
+- printMessage: 콘솔창에 출력한다.
+
diff --git a/src/main/.DS_Store b/src/main/.DS_Store
new file mode 100644
index 00000000..068ac138
Binary files /dev/null and b/src/main/.DS_Store differ
diff --git a/src/main/java/.DS_Store b/src/main/java/.DS_Store
new file mode 100644
index 00000000..d0f2c78a
Binary files /dev/null and b/src/main/java/.DS_Store differ
diff --git a/src/main/java/baseballGame/BaseballGame.java b/src/main/java/baseballGame/BaseballGame.java
new file mode 100644
index 00000000..3eb86fe0
--- /dev/null
+++ b/src/main/java/baseballGame/BaseballGame.java
@@ -0,0 +1,90 @@
+package baseballGame;
+import java.util.Scanner;
+public class BaseballGame {
+    protected int[] answer; //컴퓨터가 정한 답
+    protected int[] userAnswer; //유저가 입력한 답
+    protected int strike;
+    protected int ball;
+    protected boolean finish;
+    BaseballGame() {
+        answer = new int[3];
+        userAnswer = new int[3];
+    }
+    void startGame() {
+        runGame();
+        Scanner sc = new Scanner(System.in);
+        int response = sc.nextInt();
+        if (response == 2) return;
+        startGame();
+    }
+    protected void runGame() {
+        finish = false;
+        setGame();
+        while (!finish) {
+            setUserAnswer();
+            evaluate();
+            printOutputMessage();
+        }
+        printFinishMessage();
+    }
+    protected int[] setGame() { //정답 세팅
+        answer[0] = (int)(Math.random() * 9) + 1;
+        answer[1] = (int)(Math.random() * 9) + 1;
+        answer[2] = (int)(Math.random() * 9) + 1;
+
+        while(answer[1] == answer[0]) {
+            answer[1] = (int)(Math.random() * 9) + 1;
+        }
+        while(answer[2] == answer[0] || answer[2] == answer[1]) {
+            answer[2] = (int)(Math.random() * 9) + 1;
+        }
+        return answer;
+    }
+    protected String receiveUserInput() {
+        String buffer;
+        Scanner sc = new Scanner(System.in);
+        buffer = sc.nextLine();
+        return buffer;
+    }
+    protected void setUserAnswer() { //유저의 입력을 받음
+        System.out.print("숫자를 입력해주세요 : ");
+        String buffer = receiveUserInput();
+        for (int i = 0; i < 3; i++) {
+            userAnswer[i] = buffer.charAt(i) - '0';
+        }
+    }
+    protected int isStrike(int idx) { // idx번째가 스트라이크인지 판단한다
+        if(answer[idx] == userAnswer[idx]) return 1;
+        return 0;
+    }
+    protected int isBall(int idx) { //idx번째가 볼인지 판단한다
+        if(answer[idx] == userAnswer[idx]) return 0;
+        if(answer[0] == userAnswer[idx] || answer[1] == userAnswer[idx] || answer[2] == userAnswer[idx]) return 1;
+        return 0;
+    }
+    protected void evaluate() { //유저 입력 결과 계산
+        strike = 0;
+        ball = 0;
+        for(int i = 0; i < 3; i++) {
+            strike += isStrike(i);
+            ball += isBall(i);
+        }
+        if(strike == 3) finish = true;
+    }
+    protected void printOutputMessage() { //결과 출력
+        if(strike == 0 && ball == 0) {
+            System.out.print("낫싱");
+        }
+        if(strike > 0) {
+            System.out.print(strike + " 스트라이크 ");
+        }
+        if(ball > 0) {
+            System.out.print(ball + "볼");
+        }
+        System.out.println();
+    }
+    protected void printFinishMessage() { //종료메시지 출력
+        System.out.println("3개의 숫자를 모두 맞히셨습니다! 게임 종료");
+        System.out.println("게임을 새로 시작하려면 1, 종료하려면 2를 입력하세요.");
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/baseballGame/BaseballTest.java b/src/main/java/baseballGame/BaseballTest.java
new file mode 100644
index 00000000..e2030baf
--- /dev/null
+++ b/src/main/java/baseballGame/BaseballTest.java
@@ -0,0 +1,27 @@
+package baseballGame;
+
+public class BaseballTest extends BaseballGame {
+
+    int[] testAnswer() {
+        setGame();
+        return answer;
+    }
+    void testSetAnswer(int[] answer) {
+        this.answer = answer;
+    }
+    void testSetUserAnswer(int[] userAnswer) {
+        this.userAnswer = userAnswer;
+    }
+    int testStrike(int[] answer, int[] userAnswer) {
+        testSetAnswer(answer);
+        testSetUserAnswer(userAnswer);
+        evaluate();
+        return strike;
+    }
+    int testBall(int[] answer, int[] userAnswer) {
+        testSetAnswer(answer);
+        testSetUserAnswer(userAnswer);
+        evaluate();
+        return ball;
+    }
+}
diff --git a/src/main/java/baseballGame/Main.java b/src/main/java/baseballGame/Main.java
new file mode 100644
index 00000000..8558177b
--- /dev/null
+++ b/src/main/java/baseballGame/Main.java
@@ -0,0 +1,8 @@
+package baseballGame;
+
+public class Main {
+    public static void main(String[] args) {
+        BaseballGame baseballgame = new BaseballGame();
+        baseballgame.startGame();
+    }
+}
\ No newline at end of file
diff --git a/src/test/.DS_Store b/src/test/.DS_Store
new file mode 100644
index 00000000..068ac138
Binary files /dev/null and b/src/test/.DS_Store differ
diff --git a/src/test/java/.DS_Store b/src/test/java/.DS_Store
new file mode 100644
index 00000000..eed9005e
Binary files /dev/null and b/src/test/java/.DS_Store differ
diff --git a/src/test/java/baseballGame/BaseballGameTest.java b/src/test/java/baseballGame/BaseballGameTest.java
new file mode 100644
index 00000000..5afa4c23
--- /dev/null
+++ b/src/test/java/baseballGame/BaseballGameTest.java
@@ -0,0 +1,33 @@
+package baseballGame;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+public class BaseballGameTest {
+    //정답, 유저정답, 스트라이크, 볼
+    @Test
+    void testAnswer() {
+        BaseballTest baseballtest = new BaseballTest();
+        int[] answer = baseballtest.testAnswer();
+        for(int i = 0; i < 3; i++)
+            assertThat(answer[i] >= 1 && answer[i] <= 9);
+    }
+    @Test
+    void testStrike() {
+        BaseballTest baseballtest = new BaseballTest();
+        int[] answer = {1, 2, 3};
+        int[] userAnswer = {1, 3, 5};
+        int strike = baseballtest.testStrike(answer, userAnswer);
+        assertThat(strike == 1);
+        //스트라이크가 1맞는지
+    }
+
+    @Test
+    void testBall() {
+        BaseballTest baseballtest = new BaseballTest();
+        int[] answer = {1, 2, 3};
+        int[] userAnswer = {1, 3, 5};
+        int ball = baseballtest.testBall(answer, userAnswer);
+        assertThat(ball == 1);
+        //볼이 1맞는지
+    }
+}
diff --git a/src/test/java/study/StringTest.java b/src/test/java/study/StringTest.java
index 43e47d90..9609007d 100644
--- a/src/test/java/study/StringTest.java
+++ b/src/test/java/study/StringTest.java
@@ -5,6 +5,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class StringTest {
+
     @Test
     void replace() {
         String actual = "abc".replace("b", "d");