Favicon works for me. I get a tomato.
In terms of the UI, a couple suggestions:
The editable numbers - i wouldn’t have know to edit them if you hadn’t told me. Maybe change the text or background color.
When the numbers go down, the word session keeps shifting slightly because the width of the line is shifting. Try to make it fixed in its position.
At the risk of going overboard, i don;t think there’s a point in having both the stop and start buttons display simultaneously. Try to combine them. (When its playing, the onnly option is to stop or pause; you can’t keep playing, etc.) Great job