Read treble-clef notes against a clock that speeds up with every answer. One miss ends the run. How long can you last, and how far can your record go?
In Infinite mode the notes keep coming and the clock gets a little faster with every answer. One mistake ends the run; your score is how many notes you read correctly in a row.
It is the honest test of automatic note recognition. When you can survive a long run with the sharps switched on, you truly know first position on the treble clef.