Explore system design for mobile free-to-play games in this 2018 GDC session, focusing on the universal resource of time. Delve into practical approaches covering player levels, progression, economy, and balance. Learn about considerations for battle mechanics, unit balancing, and cost optimization. Gain insights from Scopely's Evan Losi as he breaks down essential elements of game design, from introduction to summary, providing a comprehensive overview of creating engaging and balanced mobile gaming experiences.