styles.css

@import "https://fonts.googleapis.com/css?family=Oswald:700";
body {
  background: black;
  
  
  height: 100vh;
  font-family: 'Oswald';
  font-weight: 700;
  color:white;
  font-size:40vh;
}
.stopwatch{
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -webkit-align-items: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-justify-content: center;
      -ms-flex-pack: center;
          justify-content: center;
}
.buttons{
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -webkit-align-items: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-justify-content: center;
      -ms-flex-pack: center;
          justify-content: center;
}
#hours,#minutes,#seconds{
  margin:20px;
}
button{
  border:1px solid white;
  background:white;
  font-size:3vh;
  text-transform: uppercase;
  margin:10px;
  cursor:pointer;
  border-radius:3px;
  padding:10px;
}
button:hover{
  background:black;
  color:white;
}