Quite enjoyable! The only thing I really have to say is 1. since there are 2 lines on the left, I assumed you have to get the number between them, 2. why is there a time signature if it doesn't really have any meaning, 3. imo the difficulty ramps up too slowly, and 4. so much more could be done with this. Multiple lines of numbers. Different numbers making different-pitched sounds. Some cooler graphics. As it is, though, it's perfectly fine.