Great tool and great tutorial! I have a sense that I have a good grasp of CSS grids now.

In my Firefox I did have an issue with the sound cutting out after a while. Chrome worked great.

And I think your voice sounded a bit robotic at times. I'm guessing the threshold on your mic is a bit to high.

Or from some segments I gathered that small sound fragments were being played in quick succession. If that is the case, I think fade in-out with some overlap would give a more natural sound. Though, do note that I almost never work with audio, so I may be far off here :).