How about adding more musical notes. For example, if the player goes further, then you can add not just a note, but some combination of notes in one dice. Or perhaps combine the note cubes into one powerful salvo. You can also add a laser attack (for the player), some mines, more allies, more rooms and bosses, as well as new game mechanics (only bosses; free mode, etc.) Waiting for a new assembly! X) Thank you for attention. (._.)