Drag notes to staff, then press the green play button. Drag them back to the top or bottom to delete. You can pause the playback or stop it and start over. The red X clears out all your notes. Change the speed by moving the tempo slider, and change the instrument for each color notes with the instrument sliders.
What I changed (BTW thank you @ScratchMyMouse) was that I added a background, and when you hit play it counts down for 3.
