This paper presents the background research, development, and playtesting results of a sustainability-focused educational game called Planet: Crisis. The new game was designed to raise sustainability awareness through a collaborative, deck-building card game. A review of the market for sustainability games showed that although sustainability games exist on the market today, very few have broken into the mainstream games market or gained recognition outside of the sustainability education field. Seeking to leverage this market opportunity and to produce an effective educational tool for use by sustainability educators, the author created and prototyped a Serious Educational Game (SEG) solution that was not only sustainability-focused but also fun to play. This paper reviews the process undertaken to develop a new SEG to help teach sustainability. Among available sustainability frameworks, the Cradle-to-Cradle (C2C) sustainability framework seemed best suited for the game, and the principles of what makes pure games, as well as what makes them enjoyable, were used to guide the design of the game. Planet: Crisis was developed and prototyped as a new collaborative, deck-building card game intended to help raise sustainability awareness and incentivize sustainable thinking in players. The game provides the opportunity for players to learn how to collaborate with other players to achieve a common sustainability goal and encourages learning, sharing, and replaying. The results of playtesting Planet: Crisis with 16 people over a period of 3 months demonstrated that the game may be helpful in teaching C2C principles although the game could be enhanced for audiences of the proposed target age. Playtesting Planet: Crisis gave the author the opportunity to speak to groups of players about sustainability. Playtesting groups showed a greater understanding of sustainability after playing Planet: Crisis. Next steps for the development of Planet: Crisis include revisions to the game based on playtesting feedback. Final game revisions and comprehensive, written rules will be necessary before Planet: Crisis will go into professional production for the marketplace.