Scalable Vector Graphics

<svg 
     viewbox="0 0 100 100"
     width="100" height="100"
     version="1.1" xmlns="http://www.w3.org/2000/svg"
>
    …
</svg>

Strokes are centered across paths by default. This may complicate width and coordinate calculation.

stroke-alignment := "inside" | "outside" | "center"

Shapes

rect

<rect x="0" y="0" width="100" height="100" stroke="black" />

line

<line x1="0" y1="0" x2="100" y2="100" stroke="black" />

polyline

<polyline points="0,0, 0,20 20,20 20,0 0,0" stroke="black" />

Each of the points defined are connected by lines.