# Register an event that starts with the current one.
	#
	# `delay` indicates the time between the begin of the current event and the begin of the new one.
	# Use 0.0 if both events should start at the same time and overlaps.
	#
	# Returns the new event information that can be used in fluent programming.
	fun add_sync(event: E, delay: Float, duration: nullable Float): EventInfo[E]
	do
		return queue.add_at(event, start + delay, duration)
	end