whether the ability is currently mid-sequence
the currently active stage, or null when not in use
Advances one turn.
the newly entered stage's name the turn a stage changes, 'done' the turn the
last stage finishes, or null when nothing changed (still mid-stage, or never started)
ends the ability early - interrupted mid-windup, say
begins the ability at its first stage; a no-op, reporting false, while already active
Staticfrom
Example