diff --git a/src/java/com/threerings/getdown/data/Application.java b/src/java/com/threerings/getdown/data/Application.java
index 7a71049..ca049c6 100644
--- a/src/java/com/threerings/getdown/data/Application.java
+++ b/src/java/com/threerings/getdown/data/Application.java
@@ -1,5 +1,5 @@
 //
-// $Id: Application.java,v 1.3 2004/07/02 17:03:33 mdb Exp $
+// $Id: Application.java,v 1.4 2004/07/06 05:13:35 mdb Exp $
 
 package com.threerings.getdown.data;
 
@@ -215,6 +215,64 @@ public class Application
         return new File(_appdir, path);
     }
 
+    /**
+     * Invokes the process associated with this application definition.
+     */
+    public Process createProcess ()
+        throws IOException
+    {
+        // create our classpath
+        StringBuffer cpbuf = new StringBuffer();
+        for (Iterator iter = _codes.iterator(); iter.hasNext(); ) {
+            if (cpbuf.length() > 0) {
+                cpbuf.append(File.pathSeparator);
+            }
+            Resource rsrc = (Resource)iter.next();
+            cpbuf.append(rsrc.getLocal().getAbsolutePath());
+        }
+
+        // we'll need the JVM, classpath, JVM args, class name and app args
+        String[] args = new String[4 + _jvmargs.size() + _appargs.size()];
+        int idx = 0;
+
+        // reconstruct the path to the JVM
+        args[idx++] = System.getProperty("java.home") +
+            File.separator + "bin" + File.separator + "java";
+
+        // add the classpath arguments
+        args[idx++] = "-classpath";
+        args[idx++] = cpbuf.toString();
+
+        // add the JVM arguments
+        for (Iterator iter = _jvmargs.iterator(); iter.hasNext(); ) {
+            args[idx++] = processArg((String)iter.next());
+        }
+
+        // add the application class name
+        args[idx++] = _class;
+
+        // finally add the application arguments
+        for (Iterator iter = _appargs.iterator(); iter.hasNext(); ) {
+            args[idx++] = processArg((String)iter.next());
+        }
+
+        Log.info("Running " + StringUtil.join(args, "\n"));
+        return Runtime.getRuntime().exec(args, null);
+    }
+
+    /** Replaces the application directory and version in any argument. */
+    protected String processArg (String arg)
+    {
+        if (arg.indexOf("%APPDIR%") != -1) {
+            arg = StringUtil.replace(
+                arg, "%APPDIR%", _appdir.getAbsolutePath());
+        }
+        if (arg.indexOf("%VERSION%") != -1) {
+            arg = StringUtil.replace(arg, "%VERSION%", "" + _version);
+        }
+        return arg;
+    }
+
     /**
      * Loads the <code>digest.txt</code> file and verifies the contents of
      * both that file and the <code>getdown.text</code> file. Then it
diff --git a/src/java/com/threerings/getdown/data/Resource.java b/src/java/com/threerings/getdown/data/Resource.java
index dc9e9a2..162fa24 100644
--- a/src/java/com/threerings/getdown/data/Resource.java
+++ b/src/java/com/threerings/getdown/data/Resource.java
@@ -1,5 +1,5 @@
 //
-// $Id: Resource.java,v 1.3 2004/07/02 17:03:33 mdb Exp $
+// $Id: Resource.java,v 1.4 2004/07/06 05:13:36 mdb Exp $
 
 package com.threerings.getdown.data;
 
@@ -39,6 +39,22 @@ public class Resource
         return _path;
     }
 
+    /**
+     * Returns the local location of this resource.
+     */
+    public File getLocal ()
+    {
+        return _local;
+    }
+
+    /**
+     * Returns the remote location of this resource.
+     */
+    public URL getRemote ()
+    {
+        return _remote;
+    }
+
     /**
      * Computes the MD5 hash of this resource's underlying file.
      * <em>Note:</m> This is both CPU and I/O intensive.
diff --git a/src/java/com/threerings/getdown/launcher/Downloader.java b/src/java/com/threerings/getdown/launcher/Downloader.java
new file mode 100644
index 0000000..fab5f82
--- /dev/null
+++ b/src/java/com/threerings/getdown/launcher/Downloader.java
@@ -0,0 +1,264 @@
+//
+// $Id: Downloader.java,v 1.1 2004/07/06 05:13:36 mdb Exp $
+
+package com.threerings.getdown.launcher;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import java.net.HttpURLConnection;
+
+import java.util.Iterator;
+import java.util.List;
+
+import com.samskivert.io.StreamUtil;
+
+import com.threerings.getdown.Log;
+import com.threerings.getdown.data.Resource;
+
+/**
+ * Handles the download of a collection of files, first issuing HTTP head
+ * requests to obtain size information and then downloading the files
+ * individually, reporting progress back via a callback interface.
+ */
+public class Downloader extends Thread
+{
+    /**
+     * An interface used to communicate status back to an external entity.
+     * <em>Note:</em> these methods are all called on the download thread,
+     * so implementors must take care to only execute thread-safe code or
+     * simply pass a message to the AWT thread, for example.
+     */
+    public interface Observer
+    {
+        /**
+         * Called before the downloader begins the series of HTTP head
+         * requests to determine the size of the files it needs to
+         * download.
+         */
+        public void resolvingDownloads ();
+
+        /**
+         * Called to inform the observer of ongoing progress toward
+         * completion of the overall downloading task.  The caller is
+         * guaranteed to get at least one call reporting 100% completion.
+         *
+         * @param percent the percent completion, in terms of total file
+         * size, of the downloads.
+         * @param remaining the estimated download time remaining in
+         * seconds, or <code>-1</code> if the time can not yet be
+         * determined.
+         */
+        public void downloadProgress (int percent, long remaining);
+
+        /**
+         * Called if a failure occurs while checking for an update or
+         * downloading a file.
+         *
+         * @param rsrc the resource that was being downloaded when the
+         * error occurred, or <code>null</code> if the failure occurred
+         * while resolving downloads.
+         * @param e the exception detailing the failure.
+         */
+        public void downloadFailed (Resource rsrc, Exception e);
+    }
+
+    /**
+     * Creates a downloader that will download the supplied list of
+     * resources and communicate with the specified observer. The {@link
+     * #start} method must be called on the downloader to initiate the
+     * download process.
+     */
+    public Downloader (List resources, Observer obs)
+    {
+        super("Downloader");
+        _resources = resources;
+        _obs = obs;
+    }
+
+    /**
+     * This method is invoked as the downloader thread and performs the
+     * actual downloading.
+     */
+    public void run ()
+    {
+        Resource current = null;
+        try {
+            // let the observer know that we're computing download size
+            if (_obs != null) {
+                _obs.resolvingDownloads();
+            }
+
+            // first compute the total size of our download
+            for (Iterator iter = _resources.iterator(); iter.hasNext(); ) {
+                discoverSize((Resource)iter.next());
+            }
+
+            // make a note of the time at which we started the download
+            _start = System.currentTimeMillis();
+
+            // now actually download the files
+            for (Iterator iter = _resources.iterator(); iter.hasNext(); ) {
+                current = (Resource)iter.next();
+                download(current);
+            }
+
+            // finally report our download completion if we did not
+            // already do so when downloading our final resource
+            if (_obs != null && !_complete) {
+                _obs.downloadProgress(100, 0);
+            }
+
+        } catch (Exception e) {
+            if (_obs != null) {
+                _obs.downloadFailed(current, e);
+            }
+        }
+    }
+
+    /**
+     * Issues a HEAD request for the specified resource and notes the
+     * amount of data we will be downloading to account for it.
+     */
+    protected void discoverSize (Resource rsrc)
+        throws IOException
+    {
+        // read the file information via an HTTP HEAD request
+        HttpURLConnection ucon = (HttpURLConnection)
+            rsrc.getRemote().openConnection();
+        ucon.setRequestMethod("HEAD");
+        ucon.connect();
+
+        // make sure we got a satisfactory response code
+        if (ucon.getResponseCode() != HttpURLConnection.HTTP_OK) {
+            String errmsg = "Unable to check up-to-date for " +
+                rsrc.getRemote() + ": " + ucon.getResponseCode();
+            throw new IOException(errmsg);
+        }
+
+        // add this resource's size to our total download size
+        _totalSize += ucon.getContentLength();
+    }
+
+    /**
+     * Downloads the specified resource from its remote location to its
+     * local location.
+     */
+    protected void download (Resource rsrc)
+        throws IOException
+    {
+        // make sure the resource's target directory exists
+        File parent = new File(rsrc.getLocal().getParent());
+        if (!parent.exists()) {
+            if (!parent.mkdirs()) {
+                Log.warning("Failed to create target directory for " +
+                            "resource '" + rsrc + "'. Download will " +
+                            "certainly fail.");
+            }
+        }
+
+        // download the resource from the specified URL
+        HttpURLConnection ucon = (HttpURLConnection)
+            rsrc.getRemote().openConnection();
+        ucon.connect();
+
+        // make sure we got a satisfactory response code
+        if (ucon.getResponseCode() != HttpURLConnection.HTTP_OK) {
+            String errmsg = "Unable to download resource " +
+                rsrc.getRemote() + ": " + ucon.getResponseCode();
+            throw new IOException(errmsg);
+        }
+
+        Log.info("Downloading resource [url=" + rsrc.getRemote() + "].");
+        InputStream in = null;
+        FileOutputStream out = null;
+        try {
+            in = ucon.getInputStream();
+            out = new FileOutputStream(rsrc.getLocal());
+            int read;
+
+            // TODO: look to see if we have a download info file
+            // containing info on potentially partially downloaded data;
+            // if so, use a "Range: bytes=HAVE-" header.
+
+            // read in the file data
+            while ((read = in.read(_buffer)) != -1) {
+                // write it out to our local copy
+                out.write(_buffer, 0, read);
+
+                // if we have no observer, then don't bother computing
+                // download statistics
+                if (_obs == null) {
+                    continue;
+                }
+
+                // note that we've downloaded some data
+                _currentSize += read;
+
+                // notify the observer if it's been sufficiently long
+                // since our last notification
+                long now = System.currentTimeMillis();
+                if ((now - _lastUpdate) >= UPDATE_DELAY) {
+                    _lastUpdate = now;
+
+                    // compute our bytes per second
+                    long secs = (now - _start) / 1000L;
+                    long bps = (secs == 0) ? 0 : (_currentSize / secs);
+
+                    // compute our percentage completion
+                    int pctdone = (int)(
+                        (_currentSize / (float)_totalSize) * 100f);
+
+                    // estimate our time remaining
+                    long remaining = (bps <= 0) ? -1 :
+                        (_totalSize - _currentSize) / bps;
+
+                    // make sure we only report 100% exactly once
+                    if (pctdone < 100 || !_complete) {
+                        _complete = (pctdone == 100);
+                        _obs.downloadProgress(pctdone, remaining);
+                    }
+                }
+            }
+
+        } finally {
+            StreamUtil.close(in);
+            StreamUtil.close(out);
+        }
+    }
+
+    /** The list of resources to be downloaded. */
+    protected List _resources;
+
+    /** The observer with whom we are communicating. */
+    protected Observer _obs;
+
+    /** Used while downloading. */
+    protected byte[] _buffer = new byte[4096];
+
+    /** The total file size in bytes to be transferred. */
+    protected long _totalSize;
+
+    /** The file size in bytes transferred thus far. */
+    protected long _currentSize;
+
+    /** The time at which the file transfer began. */
+    protected long _start;
+
+    /** The current transfer rate in bytes per second. */
+    protected long _bytesPerSecond;
+
+    /** The time at which the last progress update was posted to the
+     * progress observer. */
+    protected long _lastUpdate;
+
+    /** Whether the download has completed and the progress observer
+     * notified. */
+    protected boolean _complete;
+
+    /** The delay in milliseconds between notifying progress observers of
+     * file download progress. */
+    protected static final long UPDATE_DELAY = 2500L;
+}
diff --git a/src/java/com/threerings/getdown/launcher/Getdown.java b/src/java/com/threerings/getdown/launcher/Getdown.java
index a5e8dec..276c8c8 100644
--- a/src/java/com/threerings/getdown/launcher/Getdown.java
+++ b/src/java/com/threerings/getdown/launcher/Getdown.java
@@ -1,5 +1,5 @@
 //
-// $Id: Getdown.java,v 1.3 2004/07/02 17:03:33 mdb Exp $
+// $Id: Getdown.java,v 1.4 2004/07/06 05:13:36 mdb Exp $
 
 package com.threerings.getdown.launcher;
 
@@ -14,6 +14,7 @@ import org.apache.commons.io.TeeOutputStream;
 
 import com.threerings.getdown.Log;
 import com.threerings.getdown.data.Application;
+import com.threerings.getdown.data.Resource;
 
 /**
  * Manages the main control for the Getdown application updater and
@@ -29,26 +30,101 @@ public class Getdown
     public void run ()
     {
         try {
-            _app.init();
+            for (int ii = 0; ii < MAX_LOOPS; ii++) {
+                _app.init();
 
-            if (_app.verifyMetadata()) {
-                Log.info("Application requires update.");
+                if (_app.verifyMetadata()) {
+                    Log.info("Application requires update.");
 
-            } else {
-                Log.info("Metadata verified.");
-                List failures = _app.verifyResources();
-                if (failures == null) {
-                    Log.info("Resources verified.");
                 } else {
-                    Log.info(failures.size() + " resources require update.");
+                    Log.info("Metadata verified.");
+                    List failures = _app.verifyResources();
+                    if (failures == null) {
+                        Log.info("Resources verified.");
+                        launch();
+                        return;
+
+                    } else {
+                        Log.info(failures.size() + " rsrcs require update.");
+                        download(failures);
+                        // now we'll loop back and try it all again
+                    }
                 }
             }
+            Log.warning("Pants! We couldn't get the job done.");
 
         } catch (Exception e) {
             Log.logStackTrace(e);
         }
     }
 
+    /**
+     * Called if the application is determined to be of an old version.
+     */
+    protected void update ()
+    {
+        Log.info("We're needin' an update Cap'n!");
+    }
+
+    /**
+     * Called if the application is determined to require resource
+     * downloads.
+     */
+    protected void download (List resources)
+    {
+        final Object lock = new Object();
+
+        // create a downloader to download our resources
+        Downloader.Observer obs = new Downloader.Observer() {
+            public void resolvingDownloads () {
+                Log.info("Resolving downloads...");
+            }
+
+            public void downloadProgress (int percent, long remaining) {
+                Log.info("Download progress " + percent + "% " +
+                         remaining + "s remaining.");
+                if (percent == 100) {
+                    synchronized (lock) {
+                        lock.notify();
+                    }
+                }
+            }
+
+            public void downloadFailed (Resource rsrc, Exception e) {
+                Log.warning("Download failed [rsrc=" + rsrc + "].");
+                Log.logStackTrace(e);
+                synchronized (lock) {
+                    lock.notify();
+                }
+            }
+        };
+        Downloader dl = new Downloader(resources, obs);
+        dl.start();
+
+        // now wait for it to complete
+        synchronized (lock) {
+            try {
+                lock.wait();
+            } catch (InterruptedException ie) {
+                Log.warning("Waitus interruptus " + ie + ".");
+            }
+        }
+    }
+
+    /**
+     * Called to launch the application if everything is determined to be
+     * ready to go.
+     */
+    protected void launch ()
+    {
+        Log.info("All systems go!");
+        try {
+            Process proc = _app.createProcess();
+        } catch (IOException ioe) {
+            Log.logStackTrace(ioe);
+        }
+    }
+
     public static void main (String[] args)
     {
         // ensure the proper parameters are passed
@@ -85,4 +161,6 @@ public class Getdown
     }
 
     protected Application _app;
+
+    protected static final int MAX_LOOPS = 5;
 }