Citations

<-- Images -->
Profile tab icon: https://www.flaticon.com/free-icon/user_1077114?term=profile&page=1&position=2&page=1&position=2&related_id=1077114&origin=search

Home tab icon: https://www.flaticon.com/free-icon/home_1946436?term=home&page=1&position=4&page=1&position=4&related_id=1946436&origin=search

Friends tab icon: https://www.flaticon.com/free-icon/friends_880594?term=friends&page=1&position=3&page=1&position=3&related_id=880594&origin=search

Tree: https://www.pngwing.com/en/free-png-zvwvk/download

<-- Code -->
Sign in: https://getbootstrap.com/docs/4.0/examples/sign-in/

Stopwatch: https://jsfiddle.net/Daniel_Hug/pvk6p/

Info icon: https://icons.getbootstrap.com/icons/info-circle/

Firebase: https://firebase.google.com/docs

Firebase Help: https://www.youtube.com/channel/UCW5YeuERMmlnqo4oq8vwUpg