  In recent years, there has been a growing application of mixed-initiative
co-creative approaches in the creation of video games. The rapid advances in
the capabilities of artificial intelligence (AI) systems further propel
creative collaboration between humans and computational agents. In this
tutorial, we present guidelines for researchers and practitioners to develop
game design tools with a high degree of mixed-initiative co-creativity
(MI-CCy). We begin by reviewing a selection of current works that will serve as
case studies and categorize them by the type of game content they address. We
introduce the MI-CCy Quantifier, a framework that can be used by researchers
and developers to assess co-creative tools on their level of MI-CCy through a
visual scheme of quantifiable criteria scales. We demonstrate the usage of the
MI-CCy Quantifier by applying it to the selected works. This analysis enabled
us to discern prevalent patterns within these tools, as well as features that
contribute to a higher level of MI-CCy. We highlight current gaps in MI-CCy
approaches within game design, which we propose as pivotal aspects to tackle in
the development of forthcoming approaches.
