Speeding up the code: There is a part of our code that is slowing down our game. It doesn't matter for this simple game, but we can speed things up by putting the sstream code in a block that only executes occasionally. After all, we don't need to update the score hundreds of times a second!

Debugging console: Let's add some more text so we can see the current frame rate. As with the score, we don't need to update this too often. Once every hundred frames will do.

Adding more trees in the background: Simply add some more tree sprites and draw them in whatever position looks good (you could have some nearer the camera, some further away).

Improving the visibility of the HUD text: We can draw simple RectangleShape objects behind the score and the FPS counter; black with a bit of transparency will look quite...