[ludwik]

Shouldn't the code say:

    position = (position + direction + 1) % 12;

Or have I misunderstood something?

[LiamPowell]

The +12 is to keep the number positive. The direction contains the movement so a +1 wouldn't make sense.

[nulptr]

The +12 there is so that % works correctly (ie the number never becomes negative)