That was pretty hard! It took me a bit over 2 hours. It took me a long time to get started, it felt impossible.
But I found a lot of satisfying "ah ah!" moments that kept me going.
Really well done, but now I don't ever want to do one of these again.
In graphics programming, if you are not done with a frame when it would be the time to show it, you can just delay it and it won't cause much problems.
In audio, if you are not done processing the data when it should be playing, you WILL hear a glitch. Is double buffering really that useful then? Can't you just maintain a write pointer into a circular buffer that is always ahead of the read pointer?
Really well done, but now I don't ever want to do one of these again.