The library uses the usual HTML/CSS/SVG coordinate system, that is:

• X values increase in the rightward direction
• Y values increase in the downward direction
• Angles are measured clockwise as depicted below

                                -y

                               -90°
                                |
        -135°                   |                    -45°
           .                    .                   .
            .             .     |     .           .
              .      .          |         .     .
                . .             |             .
                .  .            |           .  .
               .     .          |         .     .
              .        .        |       .        .
             .           .      |     .           .
            .              .    |   .              .
  -180°     .                .  | .                .
   -x   ------------------------O------------------------- 0° +x
  +180°     .                 . |.                 ..
            .               .   |  .               .
            .             .     |    .             .
             .          .       |      .          .
              .       .         |        .       .
               .    .           |          .    .
                . .             |            . .
                .               |             .
              .      .          |               .
            .              .    .     .           .
           .                    |                   .
       +135°                    |                   +45°
                               +90°

                                +y