Added an automatic updater for new releases.

opsu! will now check for updates upon launching, and will prompt the user to download and run a newer version, if available.
- The remote version file is just the filled "version" file, currently located in the gh-pages branch.
- The new version is downloaded to the working directory, and launched with ProcessBuilder.

Related changes:
- Added "file" property (containing the download URL) to "version" file.
- Added maven-artifact dependency for version comparisons.
- Added methods in Downloads class to retrieve the constructor parameters.
- Moved method for showing exit confirmation dialogs into UI.
- Moved method for reading from URLs into Utils.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

pom.xml

@@ -191,5 +191,10 @@
 			<artifactId>jna-platform</artifactId>
 			<version>4.1.0</version>
 		</dependency>
+		<dependency>
+			<groupId>org.apache.maven</groupId>
+			<artifactId>maven-artifact</artifactId>
+			<version>3.0.3</version>
+		</dependency>
 	</dependencies>
 </project>

res/version

@@ -1,2 +1,3 @@
 version=${pom.version}
-build.date=${timestamp}
+file=https://github.com/itdelatrisu/opsu/releases/download/${pom.version}/opsu-${pom.version}.jar
+build.date=${timestamp}

src/itdelatrisu/opsu/Container.java

@@ -20,6 +20,7 @@ package itdelatrisu.opsu;
 
 import itdelatrisu.opsu.audio.MusicController;
 import itdelatrisu.opsu.downloads.DownloadList;
+import itdelatrisu.opsu.downloads.Updater;
 
 import org.lwjgl.opengl.Display;
 import org.newdawn.slick.AppGameContainer;
@@ -76,8 +77,10 @@ public class Container extends AppGameContainer {
 			}
 		}
 
-		if (forceExit)
-			Opsu.exit();
+		if (forceExit) {
+			Opsu.close();
+			System.exit(0);
+		}
 	}
 
 	@Override
@@ -128,8 +131,14 @@ public class Container extends AppGameContainer {
 	@Override
 	public void exit() {
 		// show confirmation dialog if any downloads are active
-		if (forceExit && DownloadList.get().hasActiveDownloads() && DownloadList.showExitConfirmation())
-			return;
+		if (forceExit) {
+			if (DownloadList.get().hasActiveDownloads() &&
+			    UI.showExitConfirmation(DownloadList.EXIT_CONFIRMATION))
+				return;
+			if (Updater.get().getStatus() == Updater.Status.UPDATE_DOWNLOADING && 
+			    UI.showExitConfirmation(Updater.EXIT_CONFIRMATION))
+				return;
+		}
 
 		super.exit();
 	}

src/itdelatrisu/opsu/ErrorHandler.java

@@ -119,7 +119,7 @@ public class ErrorHandler {
 						String issueTitle = (error != null) ? error : e.getMessage();
 						StringBuilder sb = new StringBuilder();
 						Properties props = new Properties();
-						props.load(ResourceLoader.getResourceAsStream("version"));
+						props.load(ResourceLoader.getResourceAsStream(Options.VERSION_FILE));
 						String version = props.getProperty("version");
 						if (version != null && !version.equals("${pom.version}")) {
 							sb.append("**Version:** ");

src/itdelatrisu/opsu/GameImage.java

@@ -447,6 +447,12 @@ public enum GameImage {
 		protected Image process_sub(Image img, int w, int h) {
 			return img.getScaledCopy((h / 17f) / img.getHeight());
 		}
+	},
+	BANG ("bang", "png", false, false) {
+		@Override
+		protected Image process_sub(Image img, int w, int h) {
+			return REPOSITORY.process_sub(img, w, h);
+		}
 	};
 
 	/** Image file types. */

src/itdelatrisu/opsu/Opsu.java

@@ -21,6 +21,7 @@ package itdelatrisu.opsu;
 import itdelatrisu.opsu.audio.MusicController;
 import itdelatrisu.opsu.db.DBController;
 import itdelatrisu.opsu.downloads.DownloadList;
+import itdelatrisu.opsu.downloads.Updater;
 import itdelatrisu.opsu.states.ButtonMenu;
 import itdelatrisu.opsu.states.DownloadsMenu;
 import itdelatrisu.opsu.states.Game;
@@ -136,6 +137,18 @@ public class Opsu extends StateBasedGame {
 		// initialize databases
 		DBController.init();
 
+		// check for updates
+		new Thread() {
+			@Override
+			public void run() {
+				try {
+					Updater.get().checkForUpdates();
+				} catch (IOException e) {
+					Log.warn("Check for updates failed.", e);
+				}
+			}
+		}.start();
+
 		// start the game
 		try {
 			// loop until force exit
@@ -150,6 +163,13 @@ public class Opsu extends StateBasedGame {
 				app.setForceExit(true);
 
 				app.start();
+
+				// run update if available
+				if (Updater.get().getStatus() == Updater.Status.UPDATE_FINAL) {
+					close();
+					Updater.get().runUpdate();
+					break;
+				}
 			}
 		} catch (SlickException e) {
 			// JARs will not run properly inside directories containing '!'
@@ -159,8 +179,6 @@ public class Opsu extends StateBasedGame {
 			else
 				ErrorHandler.error("Error while creating game container.", e, true);
 		}
-
-		Opsu.exit();
 	}
 
 	@Override
@@ -191,16 +209,20 @@ public class Opsu extends StateBasedGame {
 		}
 
 		// show confirmation dialog if any downloads are active
-		if (DownloadList.get().hasActiveDownloads() && DownloadList.showExitConfirmation())
+		if (DownloadList.get().hasActiveDownloads() &&
+		    UI.showExitConfirmation(DownloadList.EXIT_CONFIRMATION))
+			return false;
+		if (Updater.get().getStatus() == Updater.Status.UPDATE_DOWNLOADING && 
+		    UI.showExitConfirmation(Updater.EXIT_CONFIRMATION))
 			return false;
 
 		return true;
 	}
 
 	/**
-	 * Closes all resources and exits the application.
+	 * Closes all resources.
 	 */
-	public static void exit() {
+	public static void close() {
 		// close databases
 		DBController.closeConnections();
 
@@ -215,7 +237,5 @@ public class Opsu extends StateBasedGame {
 				ErrorHandler.error("Failed to close server socket.", e, false);
 			}
 		}
-
-		System.exit(0);
 	}
 }

src/itdelatrisu/opsu/Options.java

@@ -69,11 +69,17 @@ public class Options {
 	/** Font file name. */
 	public static final String FONT_NAME = "kochi-gothic.ttf";
 
+	/** Version file name. */
+	public static final String VERSION_FILE = "version";
+
 	/** Repository address. */
-	public static URI REPOSITORY_URI = URI.create("https://github.com/itdelatrisu/opsu");
+	public static final URI REPOSITORY_URI = URI.create("https://github.com/itdelatrisu/opsu");
 
 	/** Issue reporting address. */
-	public static String ISSUES_URL = "https://github.com/itdelatrisu/opsu/issues/new?title=%s&body=%s";
+	public static final String ISSUES_URL = "https://github.com/itdelatrisu/opsu/issues/new?title=%s&body=%s";
+
+	/** Address containing the latest version file. */
+	public static final String VERSION_REMOTE = "https://raw.githubusercontent.com/itdelatrisu/opsu/gh-pages/version";
 
 	/** The beatmap directory. */
 	private static File beatmapDir;

src/itdelatrisu/opsu/UI.java

@@ -21,6 +21,9 @@ package itdelatrisu.opsu;
 import java.util.Iterator;
 import java.util.LinkedList;
 
+import javax.swing.JOptionPane;
+import javax.swing.UIManager;
+
 import itdelatrisu.opsu.audio.SoundController;
 
 import org.newdawn.slick.Animation;
@@ -571,4 +574,20 @@ public class UI {
 		Utils.COLOR_BLACK_ALPHA.a = oldAlphaB;
 		Utils.COLOR_WHITE_ALPHA.a = oldAlphaW;
 	}
+
+	/**
+	 * Shows a confirmation dialog (used before exiting the game).
+	 * @param message the message to display
+	 * @return true if user selects "yes", false otherwise
+	 */
+	public static boolean showExitConfirmation(String message) {
+		try {
+			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
+		} catch (Exception e) {
+			ErrorHandler.error("Could not set system look and feel for exit confirmation.", e, true);
+		}
+		int n = JOptionPane.showConfirmDialog(null, message, "Warning",
+				JOptionPane.YES_NO_OPTION, JOptionPane.WARNING_MESSAGE);
+		return (n != JOptionPane.YES_OPTION);
+	}
 }

src/itdelatrisu/opsu/Utils.java

@@ -20,12 +20,19 @@ package itdelatrisu.opsu;
 
 import itdelatrisu.opsu.audio.SoundController;
 import itdelatrisu.opsu.audio.SoundEffect;
+import itdelatrisu.opsu.downloads.Download;
 import itdelatrisu.opsu.downloads.DownloadNode;
 
 import java.awt.Font;
 import java.awt.image.BufferedImage;
+import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.SocketTimeoutException;
+import java.net.URL;
 import java.nio.ByteBuffer;
 import java.nio.IntBuffer;
 import java.text.SimpleDateFormat;
@@ -394,6 +401,9 @@ public class Utils {
 	 * @author Sarel Botha (http://stackoverflow.com/a/5626340)
 	 */
 	public static String cleanFileName(String badFileName, char replace) {
+		if (badFileName == null)
+			return null;
+
 		boolean doReplace = (replace > 0 && Arrays.binarySearch(illegalChars, replace) < 0);
 	    StringBuilder cleanName = new StringBuilder();
 	    for (int i = 0, n = badFileName.length(); i < n; i++) {
@@ -500,4 +510,39 @@ public class Utils {
 			list.add(str);
 		return list;
     }
+
+	/**
+	 * Returns a the contents of a URL as a string.
+	 * @param url the remote URL
+	 * @return the contents as a string, or null if any error occurred
+	 */
+	public static String readDataFromUrl(URL url) throws IOException {
+		// open connection
+		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
+		conn.setConnectTimeout(Download.CONNECTION_TIMEOUT);
+		conn.setReadTimeout(Download.READ_TIMEOUT);
+		conn.setUseCaches(false);
+		try {
+			conn.connect();
+		} catch (SocketTimeoutException e) {
+			Log.warn("Connection to server timed out.", e);
+			throw e;
+		}
+
+		if (Thread.interrupted())
+			return null;
+
+		// read contents
+		try (InputStream in = conn.getInputStream()) {
+			BufferedReader rd = new BufferedReader(new InputStreamReader(in));
+			StringBuilder sb = new StringBuilder();
+			int c;
+			while ((c = rd.read()) != -1)
+				sb.append((char) c);
+			return sb.toString();
+		} catch (SocketTimeoutException e) {
+			Log.warn("Connection to server timed out.", e);
+			throw e;
+		}
+	}
 }

src/itdelatrisu/opsu/downloads/BloodcatServer.java

@@ -19,15 +19,11 @@
 package itdelatrisu.opsu.downloads;
 
 import itdelatrisu.opsu.ErrorHandler;
+import itdelatrisu.opsu.Utils;
 
-import java.io.BufferedReader;
 import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
 import java.io.UnsupportedEncodingException;
-import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
-import java.net.SocketTimeoutException;
 import java.net.URL;
 import java.net.URLEncoder;
 
@@ -98,36 +94,15 @@ public class BloodcatServer implements DownloadServer {
 	 * @return the JSON object
 	 * @author Roland Illig (http://stackoverflow.com/a/4308662)
 	 */
-	public static JSONObject readJsonFromUrl(URL url) throws IOException {
-		// open connection
-		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
-		conn.setConnectTimeout(Download.CONNECTION_TIMEOUT);
-		conn.setReadTimeout(Download.READ_TIMEOUT);
-		conn.setUseCaches(false);
-		try {
-			conn.connect();
-		} catch (SocketTimeoutException e) {
-			ErrorHandler.error("Connection to server timed out.", e, false);
-			throw e;
-		}
-
-		if (Thread.interrupted())
-			return null;
-
-		// read JSON
+	private static JSONObject readJsonFromUrl(URL url) throws IOException {
+		String s = Utils.readDataFromUrl(url);
 		JSONObject json = null;
-		try (InputStream in = conn.getInputStream()) {
-			BufferedReader rd = new BufferedReader(new InputStreamReader(in));
-			StringBuilder sb = new StringBuilder();
-			int c;
-			while ((c = rd.read()) != -1)
-				sb.append((char) c);
-			json = new JSONObject(sb.toString());
-		} catch (SocketTimeoutException e) {
-			ErrorHandler.error("Connection to server timed out.", e, false);
-			throw e;
-		} catch (JSONException e1) {
-			ErrorHandler.error("Failed to create JSON object.", e1, true);
+		if (s != null) {
+			try {
+				json = new JSONObject(s);
+			} catch (JSONException e) {
+				ErrorHandler.error("Failed to create JSON object.", e, true);
+			}
 		}
 		return json;
 	}

src/itdelatrisu/opsu/downloads/Download.java

@@ -138,9 +138,19 @@ public class Download {
 			return;
 		}
 		this.localPath = localPath;
-		this.rename = rename;
+		this.rename = Utils.cleanFileName(rename, '-');
 	}
 
+	/**
+	 * Returns the remote download URL.
+	 */
+	public URL getRemoteURL() { return url; }
+
+	/**
+	 * Returns the local path to save the download (after renamed).
+	 */
+	public String getLocalPath() { return (rename != null) ? rename : localPath; }
+
 	/**
 	 * Sets the download listener.
 	 * @param listener the listener to set
@@ -187,9 +197,8 @@ public class Download {
 						rbc.close();
 						fos.close();
 						if (rename != null) {
-							String cleanedName = Utils.cleanFileName(rename, '-');
 							Path source = new File(localPath).toPath();
-							Files.move(source, source.resolveSibling(cleanedName), StandardCopyOption.REPLACE_EXISTING);
+							Files.move(source, source.resolveSibling(rename), StandardCopyOption.REPLACE_EXISTING);
 						}
 						if (listener != null)
 							listener.completed();

src/itdelatrisu/opsu/downloads/DownloadList.java

@@ -18,7 +18,6 @@
 
 package itdelatrisu.opsu.downloads;
 
-import itdelatrisu.opsu.ErrorHandler;
 import itdelatrisu.opsu.downloads.Download.Status;
 
 import java.util.ArrayList;
@@ -27,9 +26,6 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
-import javax.swing.JOptionPane;
-import javax.swing.UIManager;
-
 /**
  * Maintains the current downloads list.
  */
@@ -37,6 +33,9 @@ public class DownloadList {
 	/** The single instance of this class. */
 	private static DownloadList list = new DownloadList();
 
+	/** The exit confirmation message. */
+	public static final String EXIT_CONFIRMATION = "Beatmap downloads are in progress.\nAre you sure you want to quit opsu!?";
+
 	/** Current list of downloads. */
 	private List<DownloadNode> nodes;
 
@@ -160,20 +159,4 @@ public class DownloadList {
 			}
 		}
 	}
-
-	/**
-	 * Shows a confirmation dialog (used before exiting the game).
-	 * @return true if user selects "yes", false otherwise
-	 */
-	public static boolean showExitConfirmation() {
-		try {
-			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-		} catch (Exception e) {
-			ErrorHandler.error("Could not set system look and feel for DownloadList.", e, true);
-		}
-		int n = JOptionPane.showConfirmDialog(null,
-				"Beatmap downloads are in progress.\nAre you sure you want to quit opsu!?",
-				"Warning", JOptionPane.YES_NO_OPTION, JOptionPane.WARNING_MESSAGE);
-		return (n != JOptionPane.YES_OPTION);
-	}
 }

src/itdelatrisu/opsu/downloads/Updater.java

@@ -0,0 +1,219 @@
+/*
+ * opsu! - an open-source osu! client
+ * Copyright (C) 2014, 2015 Jeffrey Han
+ *
+ * opsu! is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * opsu! is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with opsu!.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package itdelatrisu.opsu.downloads;
+
+import itdelatrisu.opsu.ErrorHandler;
+import itdelatrisu.opsu.Options;
+import itdelatrisu.opsu.UI;
+import itdelatrisu.opsu.Utils;
+import itdelatrisu.opsu.downloads.Download.DownloadListener;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.StringReader;
+import java.net.URL;
+import java.util.Properties;
+
+import org.apache.maven.artifact.versioning.DefaultArtifactVersion;
+import org.newdawn.slick.util.ResourceLoader;
+
+/**
+ * Handles automatic program updates.
+ */
+public class Updater {
+	/** The single instance of this class. */
+	private static Updater updater = new Updater();
+
+	/** The exit confirmation message. */
+	public static final String EXIT_CONFIRMATION = "An opsu! update is being downloaded.\nAre you sure you want to quit opsu!?";
+
+	/**
+	 * Returns the single instance of this class.
+	 */
+	public static Updater get() { return updater; }
+
+	/** Updater status. */
+	public enum Status {
+		INITIAL (""),
+		CHECKING ("Checking for updates..."),
+		CONNECTION_ERROR ("Connection error."),
+		INTERNAL_ERROR ("Internal error."),
+		UP_TO_DATE ("Up to date!"),
+		UPDATE_AVAILABLE ("Update available!\nClick to download."),
+		UPDATE_DOWNLOADING ("Downloading update...") {
+			@Override
+			public String getDescription() {
+				Download d = updater.download;
+				if (d != null && d.getStatus() == Download.Status.DOWNLOADING) {
+					return String.format("Downloading update...\n%.1f%% complete (%s/%s)",
+							d.getProgress(), Utils.bytesToString(d.readSoFar()), Utils.bytesToString(d.contentLength()));
+				} else
+					return super.getDescription();
+			}
+		},
+		UPDATE_DOWNLOADED ("Download complete.\nClick to restart."),
+		UPDATE_FINAL ("Update queued.");
+
+		/** The status description. */
+		private String description;
+
+		/**
+		 * Constructor.
+		 * @param description the status description
+		 */
+		Status(String description) {
+			this.description = description;
+		}
+
+		/**
+		 * Returns the status description.
+		 */
+		public String getDescription() { return description; }
+	};
+
+	/** The current updater status. */
+	private Status status;
+
+	/** The current and latest versions. */
+	private DefaultArtifactVersion currentVersion, latestVersion;
+
+	/** The download object. */
+	private Download download;
+
+	/**
+	 * Constructor.
+	 */
+	private Updater() {
+		status = Status.INITIAL;
+	}
+
+	/**
+	 * Returns the updater status.
+	 */
+	public Status getStatus() { return status; }
+
+	/**
+	 * Returns whether or not the updater button should be displayed.
+	 */
+	public boolean showButton() {
+		return (status == Status.UPDATE_AVAILABLE || status == Status.UPDATE_DOWNLOADED || status == Status.UPDATE_DOWNLOADING);
+	}
+
+	/**
+	 * Returns the version from a set of properties.
+	 * @param props the set of properties
+	 * @return the version, or null if not found
+	 */
+	private DefaultArtifactVersion getVersion(Properties props) {
+		String version = props.getProperty("version");
+		if (version == null || version.equals("${pom.version}")) {
+			status = Status.INTERNAL_ERROR;
+			return null;
+		} else
+			return new DefaultArtifactVersion(version);
+	}
+
+	/**
+	 * Checks the program version against the version file on the update server.
+	 */
+	public void checkForUpdates() throws IOException {
+		if (status != Status.INITIAL)
+			return;
+
+		status = Status.CHECKING;
+
+		// get current version
+		Properties props = new Properties();
+		props.load(ResourceLoader.getResourceAsStream(Options.VERSION_FILE));
+		if ((currentVersion = getVersion(props)) == null)
+			return;
+
+		// get latest version
+		String s = Utils.readDataFromUrl(new URL(Options.VERSION_REMOTE));
+		if (s == null) {
+			status = Status.CONNECTION_ERROR;
+			return;
+		}
+		props = new Properties();
+		props.load(new StringReader(s));
+		if ((latestVersion = getVersion(props)) == null)
+			return;
+
+		// compare versions
+		if (latestVersion.compareTo(currentVersion) <= 0)
+			status = Status.UP_TO_DATE;
+		else {
+			String updateURL = props.getProperty("file");
+			if (updateURL == null) {
+				status = Status.INTERNAL_ERROR;
+				return;
+			}
+			status = Status.UPDATE_AVAILABLE;
+			String localPath = String.format("%s%copsu-update-%s",
+					System.getProperty("user.dir"), File.separatorChar, latestVersion.toString());
+			String rename = String.format("opsu-%s.jar", latestVersion.toString());
+			download = new Download(updateURL, localPath, rename);
+			download.setListener(new DownloadListener() {
+				@Override
+				public void completed() {
+					status = Status.UPDATE_DOWNLOADED;
+					UI.sendBarNotification("Update has finished downloading.");
+				}
+			});
+		}
+	}
+
+	/**
+	 * Starts the download, if available.
+	 */
+	public void startDownload() {
+		if (status != Status.UPDATE_AVAILABLE || download == null || download.getStatus() != Download.Status.WAITING)
+			return;
+
+		status = Status.UPDATE_DOWNLOADING;
+		download.start();
+	}
+
+	/**
+	 * Prepares to run the update when the application closes.
+	 */
+	public void prepareUpdate() {
+		if (status != Status.UPDATE_DOWNLOADED || download == null || download.getStatus() != Download.Status.COMPLETE)
+			return;
+
+		status = Status.UPDATE_FINAL;
+	}
+
+	/**
+	 * Hands over execution to the updated file, if available.
+	 */
+	public void runUpdate() {
+		if (status != Status.UPDATE_FINAL)
+			return;
+
+		try {
+			// TODO: it is better to wait for the process? is this portable?
+			ProcessBuilder pb = new ProcessBuilder("java", "-jar", download.getLocalPath());
+			pb.start();
+		} catch (IOException e) {
+			status = Status.INTERNAL_ERROR;
+			ErrorHandler.error("Failed to start new process.", e, true);
+		}
+	}
+}

src/itdelatrisu/opsu/states/MainMenu.java

@@ -32,6 +32,7 @@ import itdelatrisu.opsu.Utils;
 import itdelatrisu.opsu.audio.MusicController;
 import itdelatrisu.opsu.audio.SoundController;
 import itdelatrisu.opsu.audio.SoundEffect;
+import itdelatrisu.opsu.downloads.Updater;
 import itdelatrisu.opsu.states.ButtonMenu.MenuState;
 
 import java.awt.Desktop;
@@ -84,6 +85,9 @@ public class MainMenu extends BasicGameState {
 	/** Button linking to repository. */
 	private MenuButton repoButton;
 
+	/** Button for installing updates. */
+	private MenuButton updateButton;
+
 	/** Application start time, for drawing the total running time. */
 	private long osuStartTime;
 
@@ -93,6 +97,9 @@ public class MainMenu extends BasicGameState {
 	/** Background alpha level (for fade-in effect). */
 	private float bgAlpha = 0f;
 
+	/** Whether or not an update notification was already sent. */
+	private boolean updateNotification = false;
+
 	/** Music position bar coordinates and dimensions. */
 	private float musicBarX, musicBarY, musicBarWidth, musicBarHeight;
 
@@ -164,13 +171,21 @@ public class MainMenu extends BasicGameState {
 		downloadsButton.setHoverExpand(1.03f, Expand.LEFT);
 
 		// initialize repository button
+		float startX = width * 0.997f, startY = height * 0.997f;
 		if (Desktop.isDesktopSupported()) {  // only if a webpage can be opened
 			Image repoImg = GameImage.REPOSITORY.getImage();
 			repoButton = new MenuButton(repoImg,
-					(width * 0.997f) - repoImg.getWidth(), (height * 0.997f) - repoImg.getHeight()
+					startX - repoImg.getWidth(), startY - repoImg.getHeight()
 			);
 			repoButton.setHoverExpand();
-		}
+			startX -= repoImg.getWidth() * 1.75f;
+		} else
+			startX -= width * 0.005f;
+
+		// initialize update button
+		Image bangImg = GameImage.BANG.getImage();
+		updateButton = new MenuButton(bangImg, startX - bangImg.getWidth(), startY - bangImg.getHeight());
+		updateButton.setHoverExpand(1.15f);
 
 		reset();
 	}
@@ -232,6 +247,27 @@ public class MainMenu extends BasicGameState {
 		if (repoButton != null)
 			repoButton.draw();
 
+		// draw update button
+		boolean showUpdateButton = Updater.get().showButton();
+		if (Updater.get().showButton()) {
+			Color updateColor = null;
+			switch (Updater.get().getStatus()) {
+			case UPDATE_AVAILABLE:
+				updateColor = Color.red;
+				break;
+			case UPDATE_DOWNLOADED:
+				updateColor = Color.green;
+				break;
+			case UPDATE_DOWNLOADING:
+				updateColor = Color.yellow;
+				break;
+			default:
+				updateColor = Color.white;
+				break;
+			}
+			updateButton.draw(updateColor);
+		}
+
 		// draw text
 		float marginX = width * 0.015f, marginY = height * 0.015f;
 		g.setFont(Utils.FONT_MEDIUM);
@@ -268,6 +304,8 @@ public class MainMenu extends BasicGameState {
 			UI.drawTooltip(g, "Next track", false);
 		else if (musicPrevious.contains(mouseX, mouseY))
 			UI.drawTooltip(g, "Previous track", false);
+		else if (showUpdateButton && updateButton.contains(mouseX, mouseY))
+			UI.drawTooltip(g, Updater.get().getStatus().getDescription(), true);
 	}
 
 	@Override
@@ -280,6 +318,7 @@ public class MainMenu extends BasicGameState {
 		exitButton.hoverUpdate(delta, mouseX, mouseY, 0.25f);
 		if (repoButton != null)
 			repoButton.hoverUpdate(delta, mouseX, mouseY);
+		updateButton.hoverUpdate(delta, mouseX, mouseY);
 		downloadsButton.hoverUpdate(delta, mouseX, mouseY);
 		// ensure only one button is in hover state at once
 		if (musicPositionBarContains(mouseX, mouseY))
@@ -347,6 +386,10 @@ public class MainMenu extends BasicGameState {
 	public void enter(GameContainer container, StateBasedGame game)
 			throws SlickException {
 		UI.enter();
+		if (!updateNotification && Updater.get().getStatus() == Updater.Status.UPDATE_AVAILABLE) {
+			UI.sendBarNotification("An opsu! update is available.");
+			updateNotification = true;
+		}
 
 		// reset button hover states if mouse is not currently hovering over the button
 		int mouseX = input.getMouseX(), mouseY = input.getMouseY();
@@ -366,6 +409,8 @@ public class MainMenu extends BasicGameState {
 			musicPrevious.resetHover();
 		if (repoButton != null && !repoButton.contains(mouseX, mouseY))
 			repoButton.resetHover();
+		if (!updateButton.contains(mouseX, mouseY))
+			updateButton.resetHover();
 		if (!downloadsButton.contains(mouseX, mouseY))
 			downloadsButton.resetHover();
 	}
@@ -424,6 +469,24 @@ public class MainMenu extends BasicGameState {
 			}
 		}
 
+		// update button actions
+		else if (Updater.get().showButton() && updateButton.contains(x, y)) {
+			switch (Updater.get().getStatus()) {
+			case UPDATE_AVAILABLE:
+				SoundController.playSound(SoundEffect.MENUHIT);
+				Updater.get().startDownload();
+				break;
+			case UPDATE_DOWNLOADED:
+				SoundController.playSound(SoundEffect.MENUHIT);
+				Updater.get().prepareUpdate();
+				container.setForceExit(false);
+				container.exit();
+				break;
+			default:
+				break;
+			}
+		}
+
 		// start moving logo (if clicked)
 		else if (!logoClicked) {
 			if (logo.contains(x, y, 0.25f)) {
@@ -519,6 +582,9 @@ public class MainMenu extends BasicGameState {
 		musicPause.resetHover();
 		musicNext.resetHover();
 		musicPrevious.resetHover();
+		if (repoButton != null)
+			repoButton.resetHover();
+		updateButton.resetHover();
 		downloadsButton.resetHover();
 	}