# Units and coordinates

> Millimetres by default, unit strings for everything else, Y growing down and rotation counter-clockwise on screen.

- Lengths are numbers in millimetres, or strings with a unit: `"0.2mm"`, `"8mil"`, `"35um"`,
  `"0.1in"`, `"1oz"` (copper, 35 um).
- A point is `[x, y]`. X grows to the right, **Y grows down**, for symbols and footprints alike.
- Rotation is in degrees, counter-clockwise as seen on screen.
- Current `"2A"` / `"500mA"`, impedance `"50ohm"`, temperature rise `"10C"`, tolerance `"10%"`.