I am little confused with the first example.
Osayamen Osaretin

"M100,100 L300,100 L200,300 z"

Keep in mind that on computer screens 0,0 is the top left corner of the screen. So, when you draw a line from 300, 100 to 200, 300 the X coordinate is smaller, hence move left by 100px, & coordinate is larger so move down by 200px. Hope this clears it up.