Improve pipeline, test coverage, and add progressive speed-up

README.md

@@ -38,22 +38,28 @@ Run unit tests:
 mvn test
 ```
 
+Run tests with Checkstyle and SpotBugs checks:
+
+```bash
+mvn verify
+```
+
 ### Without Maven
 
 If you only have the JDK, compile every `.java` file under `src/main/java`, then run `Game`:
 
-**macOS / Linux (shell expands the glob):**
+**macOS / Linux:**
 
 ```bash
-javac -d out -encoding UTF-8 src/main/java/*.java
-java -cp out Game
+javac -d out -encoding UTF-8 src/main/java/com/mapna/snake/*.java
+java -cp out com.mapna.snake.Game
 ```
 
 **Windows (PowerShell):**
 
 ```powershell
-javac -d out -encoding UTF-8 (Get-ChildItem -Path src\main\java\*.java).FullName
-java -cp out Game
+javac -d out -encoding UTF-8 (Get-ChildItem -Recurse -Path src\main\java\*.java).FullName
+java -cp out com.mapna.snake.Game
 ```
 
 The window icon loads from the classpath when run via Maven; with plain `javac`/`java`, the app falls back to `src/main/resources/images/icon.png` on disk.
@@ -64,7 +70,7 @@ The window icon loads from the classpath when run via Maven; with plain `javac`/
 |--------|------|
 | Move | **W A S D** or **arrow keys** |
 | Pause / resume | **P** |
-| Restart (after game over) | **R** |
+| Restart (after game over or win) | **R** |
 | Quit | **Esc** |
 
 ## Screenshots
@@ -87,6 +93,10 @@ The window icon loads from the classpath when run via Maven; with plain `javac`/
 
 ![Game over screenshot](docs/images/screenshot3.png)
 
+## Gameplay
+
+The snake speeds up as it grows — after eating 10 pieces of food the tick rate begins to decrease, making the game progressively harder. Fill the entire board to win.
+
 ## High score
 
 The best score is stored in **`highscore.txt`** in the process **working directory** (usually the folder you run the game from). That file is ignored by Git (see `.gitignore`).

config/checkstyle/checkstyle.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+    "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+  <property name="severity" value="error"/>
+  <property name="charset" value="UTF-8"/>
+
+  <module name="NewlineAtEndOfFile"/>
+  <module name="FileTabCharacter"/>
+  <module name="LineLength">
+    <property name="max" value="140"/>
+    <property name="ignorePattern" value="^package.*|^import.*"/>
+  </module>
+
+  <module name="TreeWalker">
+    <!-- Imports -->
+    <module name="AvoidStarImport"/>
+    <module name="UnusedImports"/>
+    <module name="RedundantImport"/>
+
+    <!-- Naming -->
+    <module name="TypeName"/>
+    <module name="MethodName"/>
+    <module name="ConstantName"/>
+    <module name="LocalVariableName"/>
+    <module name="ParameterName"/>
+    <module name="MemberName"/>
+
+    <!-- Coding -->
+    <module name="FallThrough"/>
+    <module name="OneStatementPerLine"/>
+    <module name="MultipleVariableDeclarations"/>
+    <module name="ModifierOrder"/>
+    <module name="UpperEll"/>
+    <module name="ArrayTypeStyle"/>
+    <module name="DefaultComesLast"/>
+    <module name="SimplifyBooleanExpression"/>
+    <module name="SimplifyBooleanReturn"/>
+    <module name="StringLiteralEquality"/>
+
+    <!-- Blocks -->
+    <module name="NeedBraces"/>
+    <module name="LeftCurly"/>
+    <module name="RightCurly"/>
+    <module name="EmptyBlock">
+      <property name="option" value="TEXT"/>
+    </module>
+  </module>
+</module>

config/spotbugs/exclude.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<FindBugsFilter>
+  <!-- Swing components are Serializable but never serialized in this app -->
+  <Match>
+    <Class name="com.mapna.snake.Board"/>
+    <Bug pattern="SE_BAD_FIELD,SE_BAD_FIELD_STORE"/>
+  </Match>
+
+  <!-- GameState is a mutable state holder — sharing the Snake reference is intentional -->
+  <Match>
+    <Class name="com.mapna.snake.GameState"/>
+    <Bug pattern="EI_EXPOSE_REP,EI_EXPOSE_REP2"/>
+  </Match>
+
+</FindBugsFilter>

pom.xml

@@ -5,14 +5,16 @@
 
   <groupId>com.mapna</groupId>
   <artifactId>javasnake</artifactId>
-  <version>1.0.0</version>
+  <version>1.1.0</version>
   <name>JavaSnake</name>
 
   <properties>
     <maven.compiler.source>21</maven.compiler.source>
     <maven.compiler.target>21</maven.compiler.target>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <junit.version>5.11.4</junit.version>
+    <checkstyle.plugin.version>3.4.0</checkstyle.plugin.version>
+    <spotbugs.plugin.version>4.8.3.1</spotbugs.plugin.version>
   </properties>
 
   <dependencies>
@@ -56,6 +58,41 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-checkstyle-plugin</artifactId>
+        <version>${checkstyle.plugin.version}</version>
+        <configuration>
+          <configLocation>config/checkstyle/checkstyle.xml</configLocation>
+          <consoleOutput>true</consoleOutput>
+          <failsOnError>true</failsOnError>
+          <includeTestSourceDirectory>true</includeTestSourceDirectory>
+        </configuration>
+        <executions>
+          <execution>
+            <id>checkstyle</id>
+            <phase>verify</phase>
+            <goals><goal>check</goal></goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>com.github.spotbugs</groupId>
+        <artifactId>spotbugs-maven-plugin</artifactId>
+        <version>${spotbugs.plugin.version}</version>
+        <configuration>
+          <effort>Max</effort>
+          <threshold>Medium</threshold>
+          <excludeFilterFile>config/spotbugs/exclude.xml</excludeFilterFile>
+        </configuration>
+        <executions>
+          <execution>
+            <id>spotbugs</id>
+            <phase>verify</phase>
+            <goals><goal>check</goal></goals>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>exec-maven-plugin</artifactId>

src/main/java/com/mapna/snake/Board.java

@@ -1,11 +1,15 @@
 package com.mapna.snake;
 
-import javax.swing.*;
-import java.awt.*;
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Graphics;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.event.KeyAdapter;
 import java.awt.event.KeyEvent;
+import javax.swing.JPanel;
+import javax.swing.SwingUtilities;
+import javax.swing.Timer;
 
 public class Board extends JPanel implements ActionListener {
   private final Timer timer = new Timer(BoardConfig.TICK_RATE_MS, this);
@@ -28,12 +32,14 @@ private void initBoard() {
     engine.reset(state);
     state.setHighScore(highScoreStore.load());
     highScoreSaved = false;
+    timer.setDelay(BoardConfig.TICK_RATE_MS);
     timer.start();
   }
 
   @Override
   public void actionPerformed(ActionEvent e) {
     engine.tick(state);
+    timer.setDelay(BoardConfig.tickRateMs(state.getSnake().growth()));
     if (state.getMode() == GameMode.PAUSED || state.getMode() == GameMode.GAME_OVER || state.getMode() == GameMode.WON) {
       timer.stop();
     }
@@ -70,6 +76,7 @@ public void keyPressed(KeyEvent e) {
           }
         }
         case KeyEvent.VK_ESCAPE -> SwingUtilities.getWindowAncestor(Board.this).dispose();
+        default -> { }
       }
     }
   }

src/main/java/com/mapna/snake/BoardConfig.java

@@ -2,6 +2,9 @@
 
 public final class BoardConfig {
   public static final int TICK_RATE_MS = 80;
+  public static final int MIN_TICK_RATE_MS = 40;
+  public static final int SPEEDUP_THRESHOLD = 10;
+  public static final int SPEED_STEP_MS = 2;
   public static final int BOARD_WIDTH = 480;
   public static final int BOARD_HEIGHT = 480;
   public static final int PIXEL_SIZE = 24;
@@ -14,4 +17,9 @@ public final class BoardConfig {
 
   private BoardConfig() {
   }
+
+  public static int tickRateMs(int growth) {
+    int speedups = Math.max(0, growth - SPEEDUP_THRESHOLD);
+    return Math.max(MIN_TICK_RATE_MS, TICK_RATE_MS - speedups * SPEED_STEP_MS);
+  }
 }

src/main/java/com/mapna/snake/BoardRenderer.java

@@ -1,6 +1,9 @@
 package com.mapna.snake;
 
-import java.awt.*;
+import java.awt.Color;
+import java.awt.Font;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
 
 public class BoardRenderer {
   private static final Font TITLE_FONT = new Font("Arial", Font.BOLD, 64);
@@ -40,18 +43,22 @@ private void paintScoreOverlay(Graphics g, GameState state) {
 
     g.setFont(CAPTION_FONT);
     g.setColor(Color.white);
-    g.drawString(highScoreText, (BoardConfig.BOARD_WIDTH - g.getFontMetrics().stringWidth(highScoreText)) / 2, BoardConfig.COMPONENT_HEIGHT / 4);
+    int hsX = (BoardConfig.BOARD_WIDTH - g.getFontMetrics().stringWidth(highScoreText)) / 2;
+    g.drawString(highScoreText, hsX, BoardConfig.COMPONENT_HEIGHT / 4);
     g.setColor(Color.yellow);
-    g.drawString(scoreText, (BoardConfig.BOARD_WIDTH - g.getFontMetrics().stringWidth(scoreText)) / 2, BoardConfig.COMPONENT_HEIGHT / 8);
+    int scoreX = (BoardConfig.BOARD_WIDTH - g.getFontMetrics().stringWidth(scoreText)) / 2;
+    g.drawString(scoreText, scoreX, BoardConfig.COMPONENT_HEIGHT / 8);
   }
 
   private void paintTitles(Graphics g, String title, String caption) {
     g.setFont(TITLE_FONT);
-    g.drawString(title, (BoardConfig.BOARD_WIDTH - g.getFontMetrics(TITLE_FONT).stringWidth(title)) / 2, BoardConfig.COMPONENT_HEIGHT / 2);
+    int titleX = (BoardConfig.BOARD_WIDTH - g.getFontMetrics(TITLE_FONT).stringWidth(title)) / 2;
+    g.drawString(title, titleX, BoardConfig.COMPONENT_HEIGHT / 2);
 
     g.setColor(Color.white);
     g.setFont(CAPTION_FONT);
-    g.drawString(caption, (BoardConfig.BOARD_WIDTH - g.getFontMetrics(CAPTION_FONT).stringWidth(caption)) / 2, BoardConfig.COMPONENT_HEIGHT * 5 / 8);
+    int captionX = (BoardConfig.BOARD_WIDTH - g.getFontMetrics(CAPTION_FONT).stringWidth(caption)) / 2;
+    g.drawString(caption, captionX, BoardConfig.COMPONENT_HEIGHT * 5 / 8);
   }
 
   private void paintGameContent(Graphics g, GameState state, Color hudColor, Color foodColor, Color snakeColor) {
@@ -63,13 +70,15 @@ private void paintGameContent(Graphics g, GameState state, Color hudColor, Color
     g2D.setPaint(Color.black);
     paintScore(g2D, state.getSnake().growth());
 
-    Point food = state.getFood();
+    Position food = state.getFood();
     g2D.setPaint(foodColor);
-    g2D.fillRect(food.x * BoardConfig.PIXEL_SIZE, food.y * BoardConfig.PIXEL_SIZE, BoardConfig.BORDERED_PIXEL_SIZE, BoardConfig.BORDERED_PIXEL_SIZE);
+    g2D.fillRect(food.x() * BoardConfig.PIXEL_SIZE, food.y() * BoardConfig.PIXEL_SIZE,
+        BoardConfig.BORDERED_PIXEL_SIZE, BoardConfig.BORDERED_PIXEL_SIZE);
 
     g2D.setPaint(snakeColor);
-    for (Point point : state.getSnake().getBody()) {
-      g2D.fillRect(point.x * BoardConfig.PIXEL_SIZE, point.y * BoardConfig.PIXEL_SIZE, BoardConfig.BORDERED_PIXEL_SIZE, BoardConfig.BORDERED_PIXEL_SIZE);
+    for (Position point : state.getSnake().getBody()) {
+      g2D.fillRect(point.x() * BoardConfig.PIXEL_SIZE, point.y() * BoardConfig.PIXEL_SIZE,
+          BoardConfig.BORDERED_PIXEL_SIZE, BoardConfig.BORDERED_PIXEL_SIZE);
     }
   }
 

src/main/java/com/mapna/snake/Game.java

@@ -1,6 +1,7 @@
 package com.mapna.snake;
 
-import javax.swing.*;
+import javax.swing.JFrame;
+import javax.swing.SwingUtilities;
 
 public class Game {
 

src/main/java/com/mapna/snake/GameEngine.java

@@ -1,6 +1,5 @@
 package com.mapna.snake;
 
-import java.awt.*;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
@@ -50,7 +49,7 @@ public void tick(GameState state) {
     }
 
     Snake snake = state.getSnake();
-    Point head = snake.nextHead(nextDirection, BoardConfig.PIXEL_WIDTH, BoardConfig.PIXEL_HEIGHT);
+    Position head = snake.nextHead(nextDirection, BoardConfig.PIXEL_WIDTH, BoardConfig.PIXEL_HEIGHT);
     boolean growing = head.equals(state.getFood());
 
     state.setDirection(nextDirection);
@@ -72,11 +71,11 @@ public void tick(GameState state) {
 
   private void spawnFood(GameState state) {
     Snake snake = state.getSnake();
-    List<Point> free = new ArrayList<>();
+    List<Position> free = new ArrayList<>();
     for (int x = 0; x < BoardConfig.PIXEL_WIDTH; x++) {
       for (int y = 0; y < BoardConfig.PIXEL_HEIGHT; y++) {
-        Point p = new Point(x, y);
-        if (!snake.containsPoint(p)) {
+        Position p = new Position(x, y);
+        if (!snake.contains(p)) {
           free.add(p);
         }
       }

src/main/java/com/mapna/snake/GameState.java

@@ -1,10 +1,8 @@
 package com.mapna.snake;
 
-import java.awt.*;
-
 public class GameState {
   private Snake snake;
-  private Point food = new Point();
+  private Position food = new Position(0, 0);
   private Direction direction = Direction.UP;
   private GameMode mode = GameMode.RUNNING;
   private int highScore = -1;
@@ -17,11 +15,11 @@ public void setSnake(Snake snake) {
     this.snake = snake;
   }
 
-  public Point getFood() {
+  public Position getFood() {
     return food;
   }
 
-  public void setFood(Point food) {
+  public void setFood(Position food) {
     this.food = food;
   }
 

src/main/java/com/mapna/snake/Position.java

@@ -0,0 +1,4 @@
+package com.mapna.snake;
+
+public record Position(int x, int y) {
+}