However, it is a position in word (16 bits), not in byte. So, the screen will move two bytes at a time horizontally. Also, the precision will be one CRTC character vertically.
The first game that used R12/R13 for both horizontal and vertical hardware scrolling is [https://www.cpc-power.com/index.php?page=detail&num=1839 Roland on the Ropes] , released in 1984.
To achieve smoother hardware scrolling, other tricks are required in complement to R12/R13. Usually, R3 is used for smooth horizontal scroll and R5 for smooth vertical scroll.
A good example of smooth hardware multidirectional scrolling game on CPC is [https://www.cpc-power.com/index.php?page=detail&num=2119 Super Cauldron], released in 1993.
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