I'm glad you like my idea! Regarding the enemy spawns, I do agree that the randomness can feel stressful in this game. At first, I wanted to have a spawn animation for the enemies, so that the player can notice their positions before spawn, but I ran out of time. But having enemies approach from outside the screen also sounds interesting. I'll be sure to look into that when I update this game.
Again, thank you a lot for the feedback :D