The MegaTangram puzzle has a full screen mode that can be started by clicking on the full screen button. Clicking again on the button goes back to normal webpage mode (in Firefox you may need to use the escape key, on Opera by right clicking it can be found as a menu option).
Full screen mode has been tested and is working well using Google Chrome, Firefox and Opera (12.1) web browsers, it is untested on safari but should work, to my knowledge fullscreen mode is not supported by internet explorer browsers.
Unfortunately for those with iPads and Android tablets, the fullscreen API is not supported on mobile browsers is not supported to my knowledge, however since the webpage resizes to suit the browser page width you can anyway get close to full screen size.
more information on full-screen support can be found here