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5.6: The Main Game Loop

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    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

        while True: # main game loop
            slideTo = None # the direction, if any, a tile should slide
            msg = 'Click tile or press arrow keys to slide.' # contains the message to show in the upper left corner.
            if mainBoard == SOLVEDBOARD:
                msg = 'Solved!'
            drawBoard(mainBoard, msg)

    In the main game loop, the slideTo variable will track which direction the player wants to slide a tile (it starts off at the beginning of the game loop as None and is set later) and the msg variable tracks what string to display at the top of the window. The program does a quick check on line 4 [64] to see if the board data structure has the same value as the solved board data structure stored in SOLVEDBOARD. If so, then the msg variable is changed to the string 'Solved!'.

    This won’t appear on the screen until drawBoard() has been called to draw it to the DISPLAYSURF Surface object (which is done on line 7 [67]) and pygame.display.update() is called to draw the display Surface object on the actual computer screen (which is done on line 291 at the end of the game loop).

    This page titled 5.6: The Main Game Loop is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Al Sweigart via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.