I’ve been having a ton of fun with Celeste. I’ll focus on the core aesthetic of challenge, which is the primary reason I enjoy the game (combined with the way you discover and develop the relevant dynamics as you play!)
The fun of Celeste’s challenge comes from the game’s level design combined with its movement dynamic. This dynamic starts very simply– you can walk, and jump. During the game’s prologue, it gradually introduces the player to additional core movement mechanics: climbing and dashing. Most of the game can be completed with these four mechanics at a basic level, alone. However, as you progress through the game, new levels introduce new mechanics that change or add to this dynamic: one level has wind that changes your speed and jump height, another introduces bubbles that give you a free additional midair dash, yet another one introduces little jellyfish you can grab into to glide; with each new movement mechanic, whole different solution spaces open up to solve each level’s “obstacle course.” You have to reason about what movement is available to you to solve the “puzzle” of how best to move through the level (“obstacle course,”) and then after that you have to execute your plan! This back-and-forth exercises and rewards deep knowledge of the dynamic as a whole; then, it rewards you again for understanding how to execute each individual movement mechanic in sequence and together as your knowledge and skill improves as you play. I think Celeste is a masterclass of an obstacle course and a masterclass in teaching mechanics gradually to the player in a way that still lets the player feel like they’re naturally uncovering and growing their own knowledge and talents, expanding their repertoire through trial and error combined with gradual introductions to new mechanics in well-designed levels.