7.12: Drawing the Screen

        DISPLAYSURF.fill(BGCOLOR)
        drawGrid()
        drawWorm(wormCoords)
        drawApple(apple)
        drawScore(len(wormCoords) - 3)
        pygame.display.update()
        FPSCLOCK.tick(FPS)

The code for drawing the screen in the runGame() function is fairly simple. Line 1 [101] fills in the entire display Surface with the background color. Lines 2 [102] to 5 [105] draw the grid, worm, apple, and score to the display Surface. Then the call to pygame.display.update() draws the display Surface to the actual computer screen.