Can't say I've tried the game in question, but my best guess would be to the look for the Options menu in the game and see if it lets you toggle it to full screen rather than windowed.
Somehow this seems a little obvious, but when not having a full screen option within the game... has anyone ever tried to zoom in on the browser page to make a game go full screen?
Note on quest score count : captured me 1 bunneh...
It would ruin the game resolution and it would look blurry. I don't suggest doing this. If the game has the option to full screen then, and only then, full screen it.
Not neccessarily... it might become blurry when a game is zoomed into a lot, but not for a mere 10-20%. That should still have good graphics left... all depends on how big the original game is to begin with.
@ Suryavrat : That's the same thing as zooming in... when lacking a slide bar to zoom in, the default keys to use are Ctrl+ (zoom in) and Ctrl- (zoom out) for most browsers.