If this sounds like your week
Small UI becomes invisible UI.
Tray icons and hidden tabs depend on you remembering to check them. A HUD reverses that relationship: the countdown stays where peripheral vision can keep doing some of the work.
Where tooling usually breaks
Peripheral vision needs a clear target.
A countdown does not need to be huge, but it does need enough presence to survive real work: full windows, calls, code, documents, and long stretches of concentration.