0 is in fact ONE

do this with pen on paper

so the circle is one, unity

if you divide the circle in two with an S (yin/yang) you have two, the symbol for 2 is a stylized s

if you further divide the right side of the circle to get three slices, you obtain the symbol for 3

if you further divide it in four, you get the cross with is the base symbol for 4

so basically you have 0,2,3,4

1 is the one from the roman version which is not of geometrical origin, but simple monkey arithmetic based on hand signs and the number of fingers

I, II, III

hand is V

both hands is X