Profile to understand why performance has decreased

[wkeeling]

The movement of the ball has become less smooth, possibly due to the new and better graphics.

Try profiling the game to discover any particular hotspots.

[wkeeling]

Other things to try:

• Strip alpha layers from all images, because we don't use any transparency (apart from exploding paddle?)
• Lose the background to see whether performance improves without it (so just use the screen itself for erasure)
• Try passing the background to surface.convert() in util.load_png()

[wkeeling]

This is hardware specific. None of the above make any difference. Game runs better on Mac.