User experience principle: Gameplay
Your game is somewhat challenging, and as levels progress, the difficulty gradually increases, which can increase player engagement and long-term game value. In addition, the unique design of enemies in the game brings players different challenges and fun.
However, in terms of gameplay, you can consider adding some additional game elements to enrich the player's gaming experience. For example, tasks that hide levels or unlock special rewards can be added, which can attract players to explore the game world more deeply and increase the playability and replay value of the game.