The 20th City 24hrs Marathon Digital Photo Contest is a unique competition spanning two consecutive days. Participants check in at 9:30 AM on Day 1 and visit four checkpoints (3 PM, 8 PM, 5 AM, 9 AM) at designated location. Each checkpoint has a different photography theme revealed sequentially. While photographers can shoot anywhere in the city, they must submit exactly four photos taken within each specific time period. In this article, I will share my inspiration behind each topic and reflection on this competition.