Drawing the HUD, home, and level-up screens

All the code in the following three code blocks goes in the drawing phase of our game loop. All we need to do is draw the appropriate Text objects during the appropriate states, in the draw section of the main game loop.

In the PLAYING state, add the following highlighted code:

    //Draw the crosshair
    window.draw(spriteCrosshair);
    // Switch to the HUD view
    window.setView(hudView);
    // Draw all the HUD elements
    window.draw(spriteAmmoIcon);
    window.draw(ammoText);
    window.draw(scoreText);
    window.draw(hiScoreText);
    window.draw(healthBar);
    window.draw(waveNumberText);
    window.draw(zombiesRemainingText);
}
if (state == State::LEVELING_UP)
{
}

The vital thing...