https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/d
Path commands are instructions that define a path to be drawn.
Each command is composed of a command letter and numbers that represent the command parameters.
SVG defines 6 types of path commands, for a total of 20 commands:
MoveTo: M , m.
LineTo: L , l , H , h , V , v.
Cubic Bézier Curve: C , c , S , s.
Quadratic Bézier Curve: Q , q , T , t.
Elliptical Arc Curve: A , a.
ClosePath: Z , z.
Explanation
m100,100: move to point(100,100)
h200: draw a 200px horizontal line from where we are
a20,20 0 0 1 20,20: draw an arc with 20px X radius, 20px Y radius, clockwise, to a point with 20px difference in X and Y axis
v200: draw a 200px vertical line from where we are
a20,20 0 0 1 -20,20: draw an arc with 20px X and Y radius, clockwise, to a point with -20px difference in X and 20px difference in Y axis
h-200: draw a -200px horizontal line from where we are
a20,20 0 0 1 -20,-20: draw an arc with 20px X and Y radius, clockwise, to a point with -20px difference in X and -20px difference in Y axis
v-200: draw a -200px vertical line from where we are
a20,20 0 0 1 20,-20: draw an arc with 20px X and Y radius, clockwise, to a point with 20px difference in X and -20px difference in Y axis
z: close the path
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