If I set both the Session and Break times to 01:00, your timer sound does not play and your timer-label does not change to Break when the timer reaches 00;00. Instead the sound and the text changes to Break right before the 01:00 of Break. This brings me to another issue with you project. I should not see 01:00 after 00:00. Instead, I should see 00:59. Why? Because when I see 01:00, that means you have added one additional second to the Break’s timer. When either timer gets to 00:00, that is the equivalent of the next timer starting at 01:00, so the next tick should be 00:59.
Just to clarify, the sequence should be:
00:00 change timer label and play sound as soon as 00:00 is displayed
01:00 this is when your’s changes timer label and plays the sound which is incorrect