diff --git a/README.md b/README.md
index 8d7e8aee..06d455dc 100644
--- a/README.md
+++ b/README.md
@@ -1 +1,96 @@
-# java-baseball-precourse
\ No newline at end of file
+# 숫자 야구 게임 기능 구현 목록
+
+## 게임 초기화 (컴퓨터)
+
+* 1에서 9까지의 서로 다른 임의의 수 3개를 생성한다.
+
+## 사용자 입력
+
+* 플레이어로부터 서로 다른 3자리의 수를 입력받는다.
+* 게임 종료 후 재시작(1) 또는 종료(2) 여부를 입력받는다.
+
+## 입력 유효성 검사
+
+* 사용자가 잘못된 값을 입력할 경우 [ERROR]로 시작하는 에러 메시지를 출력한다.
+* 에러 메시지 출력 후 게임을 종료하지 않고 다시 입력을 받는다.
+
+## 게임 결과 판정 (볼/스트라이크 계산)
+
+* 컴퓨터의 수와 플레이어의 수를 비교하여 결과를 계산한다.
+* 같은 수가 같은 자리에 있으면 스트라이크.
+* 같은 수가 다른 자리에 있으면 볼.
+* 같은 수가 전혀 없으면 낫싱.
+
+## 결과 출력
+
+* 계산된 볼, 스트라이크 개수를 출력한다 (예: 1볼 1스트라이크, 낫싱).
+* 3개의 숫자를 모두 맞히면(3스트라이크) 게임 종료 문구를 출력한다.
+
+```mermaid
+classDiagram
+    class Application {
+        <<Entrypoint>>
+        +main(args: String[]): void
+    }
+
+    class GameFlowController {
+        <<Controller>>
+        -secretModel: SecretNumberModel
+        -playerInputValidator: PlayerInputValidator
+        -hintModel: HintCalculatorModel
+        -gameOutput: GameOutput
+        -gameInput: GameInput
+        +start(): void
+        -askRestart(): boolean
+    }
+
+    class GameInput {
+        <<IO>>
+        -scanner: java.util.Scanner
+        +readLine(): String
+    }
+
+    class PlayerInputValidator {
+        <<Validator>>
+        +isValidInput(input: String): boolean
+        +toDigits(input: String): java.util.List<Integer>
+    }
+
+    class SecretNumberModel {
+        <<Model>>
+        -secret: java.util.List<Integer>
+        +generateSecret(): void
+        +getSecret(): java.util.List<Integer>
+    }
+
+    class HintCalculatorModel {
+        <<Model>>
+        +calculate(secret: java.util.List<Integer>, guess: java.util.List<Integer>): HintResultModel
+    }
+
+    class HintResultModel {
+        <<ValueObject>>
+        -strikes: int
+        -balls: int
+        +getStrikes(): int
+        +toString(): String
+    }
+
+    class GameOutput {
+        <<View>>
+        +showPromptForGuess(): void
+        +showHint(result: HintResultModel): void
+        +showWinAndPromptRestart(): void
+        +showError(message: String): void
+        +showExitMessage(): void
+    }
+
+    Application --> GameFlowController: starts
+    GameFlowController --> SecretNumberModel: "정답 생성 요청"
+    GameFlowController --> PlayerInputValidator: "입력 검증/숫자 변환 요청"
+    GameFlowController --> HintCalculatorModel: "판정 로직 실행"
+    GameFlowController --> GameOutput: "결과/메시지 출력 요청"
+    GameFlowController --> GameInput: "입력(readLine) 요청"
+    HintCalculatorModel ..> HintResultModel: returns
+    GameOutput ..> HintResultModel: displays
+```
\ No newline at end of file
diff --git a/src/main/java/.gitkeep b/src/main/java/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/src/main/java/Application.java b/src/main/java/Application.java
new file mode 100644
index 00000000..874a96b1
--- /dev/null
+++ b/src/main/java/Application.java
@@ -0,0 +1,7 @@
+import baseball.GameFlowController;
+
+public class Application {
+	public static void main(String[] args) {
+		new GameFlowController().start();
+	}
+}
diff --git a/src/main/java/baseball/GameFlowController.java b/src/main/java/baseball/GameFlowController.java
new file mode 100644
index 00000000..93e362dc
--- /dev/null
+++ b/src/main/java/baseball/GameFlowController.java
@@ -0,0 +1,54 @@
+package baseball;
+
+import java.util.List;
+import java.util.Scanner;
+
+public class GameFlowController {
+	private final SecretNumberModel secretModel = new SecretNumberModel();
+	private final PlayerInputValidator playerInputValidator = new PlayerInputValidator();
+	private final HintCalculatorModel hintModel = new HintCalculatorModel();
+	private final GameOutput gameOutput = new GameOutput();
+	private final GameInput gameInput = new GameInput(new Scanner(System.in));
+
+	private boolean askRestart() {
+		while (true) {
+			String choice = gameInput.readLine();
+			if ("1".equals(choice))
+				return true;
+			if ("2".equals(choice))
+				return false;
+			gameOutput.showError("1 또는 2만 입력 가능합니다.");
+		}
+	}
+
+	public void start() {
+		boolean running = true;
+		while (running) {
+			secretModel.generateSecret();
+			List<Integer> secret = secretModel.getSecret();
+
+			while (true) {
+				gameOutput.showPromptForGuess();
+				String line = gameInput.readLine();
+				if (!playerInputValidator.isValidInput(line)) {
+					gameOutput.showError("입력은 서로 다른 3개의 숫자(1-9)여야 합니다.");
+					continue;
+				}
+				List<Integer> guess = playerInputValidator.toDigits(line);
+				HintResultModel hint = hintModel.calculate(secret, guess);
+				gameOutput.showHint(hint);
+				if (hint.getStrikes() == 3) {
+					gameOutput.showWinAndPromptRestart();
+					boolean restart = askRestart();
+					if (restart) {
+						break;
+					} else {
+						running = false;
+						break;
+					}
+				}
+			}
+		}
+		gameOutput.showExitMessage();
+	}
+}
diff --git a/src/main/java/baseball/GameInput.java b/src/main/java/baseball/GameInput.java
new file mode 100644
index 00000000..1d464ba6
--- /dev/null
+++ b/src/main/java/baseball/GameInput.java
@@ -0,0 +1,16 @@
+package baseball;
+
+import java.util.Scanner;
+
+public class GameInput {
+
+	private final Scanner scanner;
+
+	public GameInput(Scanner scanner) {
+		this.scanner = scanner;
+	}
+
+	public String readLine() {
+		return scanner.nextLine().strip();
+	}
+}
diff --git a/src/main/java/baseball/GameOutput.java b/src/main/java/baseball/GameOutput.java
new file mode 100644
index 00000000..0ae97bc8
--- /dev/null
+++ b/src/main/java/baseball/GameOutput.java
@@ -0,0 +1,25 @@
+package baseball;
+
+public class GameOutput {
+
+	public void showHint(HintResultModel result) {
+		System.out.println(result.toString());
+	}
+
+	public void showError(String message) {
+		System.out.println("[ERROR] " + message);
+	}
+
+	public void showWinAndPromptRestart() {
+		System.out.println("3스트라이크! 승리했습니다.");
+		System.out.println("게임을 재시작하려면 1, 종료하려면 2를 입력하세요.");
+	}
+
+	public void showPromptForGuess() {
+		System.out.println("서로 다른 3자리 숫자를 입력하세요 (각 자리 1-9):");
+	}
+
+	public void showExitMessage() {
+		System.out.println("게임을 종료합니다.");
+	}
+}
diff --git a/src/main/java/baseball/HintCalculatorModel.java b/src/main/java/baseball/HintCalculatorModel.java
new file mode 100644
index 00000000..9f695ea7
--- /dev/null
+++ b/src/main/java/baseball/HintCalculatorModel.java
@@ -0,0 +1,18 @@
+package baseball;
+
+import java.util.List;
+
+public class HintCalculatorModel {
+	public HintResultModel calculate(List<Integer> secret, List<Integer> guess) {
+		int strikes = 0;
+		int balls = 0;
+		for (int i = 0; i < 3; i++) {
+			if (guess.get(i).equals(secret.get(i))) {
+				strikes++;
+			} else if (secret.contains(guess.get(i))) {
+				balls++;
+			}
+		}
+		return new HintResultModel(strikes, balls);
+	}
+}
diff --git a/src/main/java/baseball/HintResultModel.java b/src/main/java/baseball/HintResultModel.java
new file mode 100644
index 00000000..698b3889
--- /dev/null
+++ b/src/main/java/baseball/HintResultModel.java
@@ -0,0 +1,32 @@
+package baseball;
+
+public class HintResultModel {
+	private final int strikes;
+	private final int balls;
+
+	public HintResultModel(int strikes, int balls) {
+		this.strikes = strikes;
+		this.balls = balls;
+	}
+
+	public int getStrikes() {
+		return strikes;
+	}
+
+	@Override
+	public String toString() {
+		if (strikes == 0 && balls == 0)
+			return "낫싱";
+		StringBuilder sb = new StringBuilder();
+		if (strikes > 0) {
+			sb.append(strikes).append("스트라이크");
+		}
+		if (balls > 0) {
+			if (strikes > 0) {
+				sb.append(" ");
+			}
+			sb.append(balls).append("볼");
+		}
+		return sb.toString();
+	}
+}
diff --git a/src/main/java/baseball/PlayerInputValidator.java b/src/main/java/baseball/PlayerInputValidator.java
new file mode 100644
index 00000000..584627f3
--- /dev/null
+++ b/src/main/java/baseball/PlayerInputValidator.java
@@ -0,0 +1,34 @@
+package baseball;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+
+public class PlayerInputValidator {
+	public boolean isValidInput(String s) {
+		if (s == null)
+			return false;
+		if (s.length() != 3)
+			return false;
+		HashSet<Character> set = new HashSet<>();
+		for (char c : s.toCharArray()) {
+			if (!Character.isDigit(c))
+				return false;
+			int d = c - '0';
+			if (d < 1 || d > 9)
+				return false;
+			set.add(c);
+		}
+		return set.size() == 3;
+	}
+
+	/*
+	 * 올바른 입력이 주어졌을 때만 호출되어야 합니다.
+	 * */
+	public List<Integer> toDigits(String s) {
+		List<Integer> list = new ArrayList<>();
+		for (char c : s.toCharArray())
+			list.add(c - '0');
+		return list;
+	}
+}
diff --git a/src/main/java/baseball/SecretNumberModel.java b/src/main/java/baseball/SecretNumberModel.java
new file mode 100644
index 00000000..652ea6a3
--- /dev/null
+++ b/src/main/java/baseball/SecretNumberModel.java
@@ -0,0 +1,21 @@
+package baseball;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class SecretNumberModel {
+	private List<Integer> secret = new ArrayList<>();
+
+	public void generateSecret() {
+		List<Integer> pool = new ArrayList<>();
+		for (int i = 1; i <= 9; i++)
+			pool.add(i);
+		Collections.shuffle(pool);
+		secret = new ArrayList<>(pool.subList(0, 3));
+	}
+
+	public List<Integer> getSecret() {
+		return new ArrayList<>(secret);
+	}
+}
diff --git a/src/test/java/.gitkeep b/src/test/java/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/src/test/java/baseball/GameInputTest.java b/src/test/java/baseball/GameInputTest.java
new file mode 100644
index 00000000..7359c759
--- /dev/null
+++ b/src/test/java/baseball/GameInputTest.java
@@ -0,0 +1,29 @@
+package baseball;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Scanner;
+
+import org.junit.jupiter.api.Test;
+
+class GameInputTest {
+
+	// 트림 기능 테스트
+	@Test
+	void readLine_trims_leading_and_trailing_spaces() {
+		Scanner scanner = new Scanner("  123  ");
+		GameInput input = new GameInput(scanner);
+
+		String result = input.readLine();
+		assertEquals("123", result);
+	}
+
+	// 일반 입력 테스트
+	@Test
+	void readLine_returns_input_as_is() {
+		Scanner scanner = new Scanner("456");
+		GameInput input = new GameInput(scanner);
+		String result = input.readLine();
+		assertEquals("456", result);
+	}
+}
\ No newline at end of file
diff --git a/src/test/java/baseball/GameOutputTest.java b/src/test/java/baseball/GameOutputTest.java
new file mode 100644
index 00000000..3298a6b9
--- /dev/null
+++ b/src/test/java/baseball/GameOutputTest.java
@@ -0,0 +1,55 @@
+package baseball;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class GameOutputTest {
+	private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
+	private final PrintStream originalOut = System.out;
+	private GameOutput view;
+
+	@BeforeEach
+	void setUp() {
+		System.setOut(new PrintStream(outContent));
+		view = new GameOutput();
+		outContent.reset();
+	}
+
+	@AfterEach
+	void tearDown() {
+		System.setOut(originalOut);
+	}
+
+	@Test
+	void showHint_prints_nothing_when_no_match() {
+		view.showHint(new HintResultModel(0, 0));
+		assertEquals("낫싱\n", outContent.toString());
+	}
+
+	@Test
+	void showHint_prints_ball_and_strike() {
+		view.showHint(new HintResultModel(2, 1));
+		assertEquals("2스트라이크 1볼\n", outContent.toString());
+	}
+
+	@Test
+	void showError_prefixes_message_with_error_tag() {
+		view.showError("입력 오류");
+		assertEquals("[ERROR] 입력 오류\n", outContent.toString());
+	}
+
+	@Test
+	void showWinAndPromptRestart_prints_two_lines() {
+		view.showWinAndPromptRestart();
+		String output = outContent.toString();
+		assertTrue(output.contains("3스트라이크! 승리했습니다."));
+		assertTrue(output.contains("게임을 재시작하려면 1, 종료하려면 2를 입력하세요."));
+	}
+}
diff --git a/src/test/java/baseball/HintCalculatorModelTest.java b/src/test/java/baseball/HintCalculatorModelTest.java
new file mode 100644
index 00000000..9404db1e
--- /dev/null
+++ b/src/test/java/baseball/HintCalculatorModelTest.java
@@ -0,0 +1,109 @@
+package baseball;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+class HintCalculatorModelTest {
+	/*
+	* public HintResultModel calculate(List<Integer> secret, List<Integer> guess) {
+		int strikes = 0;
+		int balls = 0;
+		for (int i = 0; i < 3; i++) {
+			if (guess.get(i).equals(secret.get(i))) {
+				strikes++;
+			} else if (secret.contains(guess.get(i))) {
+				balls++;
+			}
+		}
+		return new HintResultModel(strikes, balls);
+	}
+	* */
+
+	private final HintCalculatorModel hintCalculator = new HintCalculatorModel();
+
+	// 1. 모든 숫자가 일치하는 경우 (3 스트라이크, 0 볼)
+	@Test
+	void calculate_all_match() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(1, 2, 3),
+			List.of(1, 2, 3)
+		);
+		assert result.getStrikes() == 3;
+		assert result.toString().equals("3스트라이크");
+	}
+
+	// 2. 일부 숫자가 위치까지 일치하는 경우 (예: 2 스트라이크, 0 볼)
+	@Test
+	void calculate_partial_strike_match() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(1, 2, 3),
+			List.of(1, 2, 4)
+		);
+		assert result.getStrikes() == 2;
+		assert result.toString().equals("2스트라이크");
+	}
+
+	@Test
+	void calculate_partial_strike_match_2() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(4, 5, 6),
+			List.of(4, 7, 6)
+		);
+		assert result.getStrikes() == 2;
+		assert result.toString().equals("2스트라이크");
+	}
+
+	@Test
+	void calculate_partial_strike_match_3() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(7, 8, 9),
+			List.of(0, 8, 9)
+		);
+		assert result.getStrikes() == 2;
+		assert result.toString().equals("2스트라이크");
+	}
+
+	// 3. 일부 숫자가 위치는 다르지만 포함되는 경우 (예: 0 스트라이크, 2 볼)
+	@Test
+	void calculate_partial_ball_match() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(1, 2, 3),
+			List.of(3, 1, 4)
+		);
+		assert result.getStrikes() == 0;
+		assert result.toString().equals("2볼");
+	}
+
+	@Test
+	void calculate_partial_ball_match_2() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(4, 5, 6),
+			List.of(6, 4, 7)
+		);
+		assert result.getStrikes() == 0;
+		assert result.toString().equals("2볼");
+	}
+
+	// 4. 숫자가 전혀 일치하지 않는 경우 (0 스트라이크, 0 볼)
+	@Test
+	void calculate_no_match() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(1, 2, 3),
+			List.of(4, 5, 6)
+		);
+		assert result.getStrikes() == 0;
+		assert result.toString().equals("낫싱");
+	}
+
+	@Test
+	void calculate_no_match_2() {
+		HintResultModel result = hintCalculator.calculate(
+			List.of(7, 8, 9),
+			List.of(1, 2, 3)
+		);
+		assert result.getStrikes() == 0;
+		assert result.toString().equals("낫싱");
+	}
+
+}
\ No newline at end of file
diff --git a/src/test/java/baseball/HintResultModelTest.java b/src/test/java/baseball/HintResultModelTest.java
new file mode 100644
index 00000000..7310ad36
--- /dev/null
+++ b/src/test/java/baseball/HintResultModelTest.java
@@ -0,0 +1,70 @@
+package baseball;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class HintResultModelTest {
+	// 0볼 0스트라이크
+	@Test
+	void testNoBallsNoStrikes() {
+		HintResultModel hint = new HintResultModel(0, 0);
+		assertEquals("낫싱", hint.toString());
+	}
+
+	// 0볼 1스트라이크
+	@Test
+	void testNoBallsOneStrike() {
+		HintResultModel hint = new HintResultModel(1, 0);
+		assertEquals("1스트라이크", hint.toString());
+	}
+
+	// 0볼 2스트라이크
+	@Test
+	void testNoBallsTwoStrikes() {
+		HintResultModel hint = new HintResultModel(2, 0);
+		assertEquals("2스트라이크", hint.toString());
+	}
+
+	// 1볼 0스트라이크
+	@Test
+	void testOneBallNoStrikes() {
+		HintResultModel hint = new HintResultModel(0, 1);
+		assertEquals("1볼", hint.toString());
+	}
+
+	// 1스트라이크 1볼 (스트라이크 먼저)
+	@Test
+	void testOneBallOneStrike() {
+		HintResultModel hint = new HintResultModel(1, 1);
+		assertEquals("1스트라이크 1볼", hint.toString());
+	}
+
+	// 2볼 0스트라이크
+	@Test
+	void testTwoBallsNoStrikes() {
+		HintResultModel hint = new HintResultModel(0, 2);
+		assertEquals("2볼", hint.toString());
+	}
+
+	// 1스트라이크 2볼 (스트라이크 먼저)
+	@Test
+	void testTwoBallsOneStrike() {
+		HintResultModel hint = new HintResultModel(1, 2);
+		assertEquals("1스트라이크 2볼", hint.toString());
+	}
+
+	// 3볼 0스트라이크
+	@Test
+	void testThreeBallsNoStrikes() {
+		HintResultModel hint = new HintResultModel(0, 3);
+		assertEquals("3볼", hint.toString());
+	}
+
+	// 0볼 3스트라이크
+	@Test
+	void testNoBallsThreeStrikes() {
+		HintResultModel hint = new HintResultModel(3, 0);
+		assertEquals("3스트라이크", hint.toString());
+	}
+}
\ No newline at end of file
diff --git a/src/test/java/baseball/PlayerInputValidatorTest.java b/src/test/java/baseball/PlayerInputValidatorTest.java
new file mode 100644
index 00000000..4a3cf9ea
--- /dev/null
+++ b/src/test/java/baseball/PlayerInputValidatorTest.java
@@ -0,0 +1,52 @@
+package baseball;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class PlayerInputValidatorTest {
+	private final PlayerInputValidator validator = new PlayerInputValidator();
+
+	//    - null 입력 -> false 반환
+	@Test
+	void testIsValidInput_NullInput() {
+		assertFalse(validator.isValidInput(null));
+	}
+
+	//    - 길이 3이 아닌 입력 (예: "12", "12333", "1234") -> false 반환
+	@Test
+	void testIsValidInput_InvalidLength() {
+		assertFalse(validator.isValidInput("12"));
+		assertFalse(validator.isValidInput("12333"));
+		assertFalse(validator.isValidInput("1234"));
+	}
+
+	//    - 숫자가 아닌 문자 포함 (예: "1a3", "12!")
+	@Test
+	void testIsValidInput_NonDigitCharacters() {
+		assertFalse(validator.isValidInput("1a3"));
+	}
+
+	//    - 1-9 범위 밖의 숫자 포함 (예: "023", "1450")
+	@Test
+	void testIsValidInput_OutOfRangeNumbers() {
+		assertFalse(validator.isValidInput("023"));
+		assertFalse(validator.isValidInput("1450"));
+	}
+
+	//    - 중복된 숫자 포함 (예: "112", "121")
+	@Test
+	void testIsValidInput_DuplicateNumbers() {
+		assertFalse(validator.isValidInput("112"));
+		assertFalse(validator.isValidInput("121"));
+	}
+
+	//    - 올바른 입력 (예: "123", "987") -> true
+	@Test
+	void testIsValidInput_ValidInput() {
+		assertTrue(validator.isValidInput("123"));
+		assertTrue(validator.isValidInput("987"));
+	}
+
+}
\ No newline at end of file
diff --git a/src/test/java/baseball/SecretNumberModelTest.java b/src/test/java/baseball/SecretNumberModelTest.java
new file mode 100644
index 00000000..f73de1a4
--- /dev/null
+++ b/src/test/java/baseball/SecretNumberModelTest.java
@@ -0,0 +1,28 @@
+package baseball;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class SecretNumberModelTest {
+	@Test
+	void testGenerateSecret() {
+		SecretNumberModel model = new SecretNumberModel();
+		model.generateSecret();
+		// 테스트 코드는 여기에서 작성합니다.
+		// 예: 비어 있지 않은지, 3자리 숫자인지, 중복이 없는지 등을 확인할 수 있습니다.
+
+		List<Integer> test = model.getSecret();
+		Assertions.assertEquals(3, test.size(), "시크릿 넘버는 3자리여야 합니다.");
+		for (Integer integer : test) {
+			Assertions.assertNotNull(integer, "시크릿 넘버의 각 자리는 null이 될 수 없습니다.");
+			Assertions.assertTrue(0 < integer && integer < 10, "시크릿 넘버의 각 자리는 한 자리 자연수여야 합니다.");
+		}
+		for (int i = 0; i < test.size(); i++) {
+			for (int j = i + 1; j < test.size(); j++) {
+				Assertions.assertNotEquals(test.get(i), test.get(j), "시크릿 넘버의 각 자리는 서로 달라야 합니다.");
+			}
+		}
+	}
+}
\ No newline at end of file