Click the flag twice, because sometimes it does weird stuff when you click the flag in the middle of your game. Read the note on the far right, and click the key on the keyboard which it represents. (There are several octaves on the staff, but only one on the keyboard. It doesn't matter what octave the shown blue note is in. If it is a high, low, or middle C, just click C.) Notice that if you click the wrong note, a saxophone instead of piano sound is played. This doesn't mean I don't like saxophones. No, no. I play the sax. I just thought it might sound funny.
I made this to help myself, and anyone else, become a better sight-reader. I did not make it to look nice. I only put it together in two or three days. This program is helping me with reading music, and I hope it helps you too. :) I plan on expanding the keyboard so that several octaves are shown.