Heyyyy I like that color line idea, maybe i will add it hehe
And talking abt the tutorial level... yeah it's kind of hard lol, it's like a challenge to test your skills and tbh i will probably nerf it a bit, especially the final part, (but anyways you can also use the practice mode that lets you even skip to the part you have struggles!)
The idea of only using a line of keys for a tutorial level seems a bit contradictory to the idea of the game tho, I want to empathize from the beginning that the keyboard is your area of game, and you shouldn't limit yourself with it and the area where the keys are shown (that's what the notes are called) is equivalent to the keyboard, so it's easy to get the hang of it
But I still appreciate your feedback and ideas for the game, I'm happy you took your time to write and play it ^ ^! (also i'll be honest with u, i've never played Project Diva lol)