Developmental strokes are basic drawings that a child should be able to perform before expecting them to write
letters (i.e. practicing writing their name). They include, in order of development: a vertical line (2- years), a
horizontal line, (2 ½ years), a circle (3-years), a cross (3 ½ -4 years), a square (4-years), a diagonal line (4 ½
years), an “X” (4 years- 11 months), a triangle (5 years-3 months). Diagonal strokes are the most difficult;
therefore the “x” and the triangle are the last to develop.

http://www.bentonstearns.k12.mn.us/PDF Downloads/Development...

Direi così.