[NTG-context] Reset environment between MetaPost graphics?

Hi, Say I’m writing a document containing many independent MetaPost figures. I don’t want to bother with enclosing each and every graphics in a ‘begingroup...endgroup’ with the appropriate ‘save’ statement. But I don’t want variables from previous graphics to leak into following ones either. Like this: % SOF \starttext Text about some topic. \startMPcode u=1cm; draw (-u, u)--origin--(u ,u); \stopMPcode Now on to another topic. \startMPcode u=2cm; % Triggers an error: Inconsistent equation (off by 28.34645) draw (-u, u)..origin..(u ,u); \stopMPcode \stoptext % EOF Is that achievable? Thanks, Vincent