In fact, even with optimizations, the default background seems to be to complex to run at full speed (so it runs only at 30 fps).
I used an alternative background the original programmer had made to run faster (60 fps).
You can still choose the original background if you prefer.
Also I updated the game to display nicer on the 16/9 screen. This is why the patch is now bigger, since there are now some more modifications to the original code.