All assets are bundled into the executable and the measured size is the size of that executable. If you download the 14k .zip file available on that web page,

All assets are bundled into the executable and the measured size is the size of that executable. If you download the 14k .zip file available on that web page, inside you will find a 128 byte .com file. In this case, there is no sound and the textures are generated procedurally.