A growing body of academic research and educational institutions are recognizing the need to incorporate sustainability learning into fundamental engineering courses. Furthermore, the recent COVID-19 global pandemic has created a sudden need to augment traditional lecture-based teaching with effective web-based learning platforms. In light of these challenges the engineering education community needs to place a greater focus on designing and testing interactive, information technology-based tools for sustainability learning. To this end, our paper presents the design and implementation of Økoengineer: a web-based game platform that supports guided discovery-based learning of sustainability concepts in engineering curricula. Økoengineer is designed to familiarize engineering students with sustainability concepts and provide them with an understanding of how sustainability can be considered in the engineering design process. Therefore, Økoengineer hosts a collection of open-ended design tasks in multiple engineering disciplines. Students can solve these tasks iteratively and receive guidance through a combination of pre-recorded lectures on sustainability concepts and discussions with domain experts. Økoengineer also aims to increase students’ learning outcomes through the use of gamified elements, including high-score leaderboards, formative feedback & peer discussions, and rewarding achievements through virtual collectible badges. The Økoengineer platform is architected for scalability and allows course instructors to easily add new learning materials and design tasks.