v2.0

Hey!

v2.0 fixes the black screen bug a lot of people were experiencing. It took way too long to work out what the problem was - the wall graphic was instantiated as a 20,000px-wide texture, which not all GPUs will accept (which is retrospect is entirely reasonable). So sometimes the creation would silently fail and render as a black screen instead.

The fix was to use multiple render targets instead of 1 giant one. As render targets disappear off the side of the screen (i.e. when the camera scrolls far enough), the render targets are cleared and moved back onto the screen.

List of changes is below:

• Fix the RenderTarget2D bug (dimensions too big)
• Add sound effects
• Tidy up code

Have fun!