You can use as many (or as few) tools, libraries, and frameworks as you'd like. If you're trying to learn something new, this might be a great way to push yourself.
Users should be able to:
Start the timer by clicking on the start link/button.
Once the user clicks start, the word start will change to stop. Then, the user can click on the stop button to make the timer stop.
Click on the gear icon to change the length (minutes and seconds) of the timer.
Once the timer finishes, the ring should change from green to red and an alert message is passed to the browser.