Fifth Door is building a platform that lets everyone create and play games with AI in any setting and with anyone. The company aims to make game development, distribution, and play accessible to all, fostering imagination, social connection, and enjoyment through interactive experiences. Co-founder Daniel Kan previously built Exec (YC W12) and was part of Cruise (YC W14). Fifth Door was founded in 2025 and is part of Y Combinator's Fall 2025 batch.