Changes
* The priority of sprite-to-sprite is fixed. Sprite 0 has a higher priority than sprite 8.
* The pixel size in high resolution is comparable to CPC's mode 1. Each pixel can be either transparent OR a colour unique for each sprite. The pixel size in multicolour is comparable to CPC's mode 0 and each pixel can be transparent or 1 of the other 3 colours.
* Each sprite can be magnified in heightand width.
* Sprite data is fetched from main RAM.
