Added new Mirror Sprites; Fixed GAME_MODE issue.

The previous handling of the GAME_MODE was done in a way that after the
Player retries a game, he/she would have to hit Play at least once before
being able to re-arrange the mirrors because the GAME_MODE of RETRIED
considers the game has already stopped, whereas the Laser is still on the
screen.

This has been fixed by considering the RETRIED mode as still being in
play, so that the user can simply press the Stop button to be able to
re-arrange the mirrors.