Make arc diagrams from text

arc Pirate Alliances
//order appearance name, group, degree

// Source -> Target weight
[Caribbean] red
  Blackbeard -> Bonnet 8
  Blackbeard -> Vane 5
  Blackbeard -> Hornigold 4
  Hornigold -> Bonnet 2

[Women Pirates] purple
  Bonny -> Rackham 9
  Bonny -> Read 7
  Rackham -> Vane 3

[West Africa] teal
  Roberts -> Davis 6

Syntax

arc Chart Title
order appearance

Source -> Target weight

Metadata Keys

Key	Description	Required
`chart`	Must be `arc`	Yes
`title`	Chart title displayed above the chart	No
`order`	Node ordering: `appearance` (default), `name`, `group`, or `degree`	No

Data Format

Each data line defines a connection between two nodes with an optional weight:

Source -> Target weight
Source -> Target

If weight is omitted, it defaults to 1. Arc thickness is proportional to weight.

Node Groups

Use [Group Name] color headers to group nodes by color:

[Captains] red
Blackbeard -> Bonnet 8
Blackbeard -> Vane 5

[Crew] blue
Bonny -> Read 7

Nodes inherit the color of the group in which they first appear.

Node Ordering

appearance — nodes appear in the order they are first mentioned (default)
name — nodes sorted alphabetically
group — nodes sorted by group, then by appearance within group
degree — nodes sorted by number of connections (most connected first)