Comment 2 for bug 1244987

lierolibre is initialized in windowed mode by design, as per http://freedesktop.org/wiki/Games/Upstream/

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It is recommended that the first time a game starts, it starts in windowed mode. Subsequent times the game should use the mode the user selected the previous time.
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There are indeed currently no menu options to toggle fullscreen, nor does the game save the previous state for next time (which is arguably something that should be implemented).

For now, the intended method for switching screen size and fullscreen is by using the F# keys, as described in the manpage:

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* Fullscreen, x2, x3 and x4 scaling via the F5, F6, F7 and F8 keys
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Does these keys work as intended for you?