A large consideration for me, when working on Subway Surfers, was the importance of giving players consistently paced discoveries and rewards. Since the infinite runs can become long, it was important for me that players were always engaged.

Rewards doesn't necessarily mean a pick-up or currency. It could even be a particularly well-paced level, which intuitively guides players to satisfying moments, like slamming into a buried cache from high up, as shown in the example below.

Another way I created engaging moments, was to tell a short story through the level design itself. In the below example, by using gameplay elements like drones and trains, I borrow tropes such as establishing shots and foreshadowing from movies, to create an "action movie"-esque level.