We're so happy to hear your proposals! We'll add music a little bit later, after we finish all basic things like save load system. As for jumps, Double jump will be unlocked later during the game. Regarding holding jump button to jump higher, there will be some basic UI to tell the player what buttons are for what and the instructions will definitely mention this "hold to jump higher" case. There will also be rebinding system, so you will be able to put the controls you love most. (the current controls were taken from basic controls of some famous metroidvania and roguelike platformer games).