void set_current_time(const Msp::Time::TimeDelta &);
const Msp::Time::TimeDelta &get_current_time() const { return current_time; }
void tick(const Msp::Time::TimeDelta &);
void set_current_time(const Msp::Time::TimeDelta &);
const Msp::Time::TimeDelta &get_current_time() const { return current_time; }
void tick(const Msp::Time::TimeDelta &);