Everything you need on one page. Official spec: SYNTAX.md.
Auto-layout tools (Mermaid, Graphviz, D2) decide where things go — great until you care where things go. Drag tools (draw.io, Excalidraw) give control but every edit is hand-work. Reladraw is the middle: positions are stated as relationships (below of, level with), so edits are one-line changes and agents can draw too.
| Declare a node | node id "Label" | node api "API" |
| Place it | … below / above / left of / right of other | node db "DB" below api |
| Diagonal placement | below-left / below-right / above-left / above-right of | node cache "Redis" above-right of api |
| Align | … level with other | node gw "GW" level with api |
| Connect | edge a -> b "label" | edge api -> db "queries" |
| Edge ports | … from: top / bottom / left / right to: … | edge api -> db from: bottom to: top |
| Group | cluster id "Label" { … } | cluster vpc "VPC" { node alb } |
| Theme | diagram theme: name | diagram theme: nord |
Open the playground with any template from the template gallery.