A sequence diagram whose lifelines are people: Ines, Unit the agent, the vault and Vex stand at the top, drawn by the kit at half size, with a dashed lifeline under each. The messages come from a few lines of text. Play sends each one as an envelope along its arrow, then the arrow draws itself and the receiver's face changes.
a -> b: text a message, a --> b: text a reply, note over a: text a note. Names: ines, unit, vault, vex. An optional [mood] at the end sets the receiver's face (happy, worried, surprised, thinking, confused, determined, calm, sad, excited, neutral) or the vault's door (open, locked, closed).
space play → step ← back