5.9: Sliding Tiles with the Keyboard

            elif event.type == KEYUP:
                # check if the user pressed a key to slide a tile
                if event.key in (K_LEFT, K_a) and isValidMove(mainBoard, LEFT):
                    slideTo = LEFT
                elif event.key in (K_RIGHT, K_d) and isValidMove(mainBoard, RIGHT):
                    slideTo = RIGHT
                elif event.key in (K_UP, K_w) and isValidMove(mainBoard, UP):
                    slideTo = UP
                elif event.key in (K_DOWN, K_s) and isValidMove(mainBoard, DOWN):
                    slideTo = DOWN

We can also let the user slide tiles by pressing keyboard keys. The if and elif statements on lines 3 [100] to 10 [107] let the user set the slideTo variable by either pressing the arrow keys or the WASD keys (explained later). Each if and elif statement also has a call to isValidMove() to make sure that the tile can slide in that direction. (We didn’t have to make this call with the mouse clicks because the checks for the neighboring blank space did the same thing.)

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