* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background-color: palevioletred;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

#container {
  color: indigo;
}

#time {
  user-select: none;
}

.digit {
  font-size: 150px;
  font-weight: bold;
}

.txt {
  font-size: 40px;
  font-weight: bold;
}

#btn_container {
  text-align: center;
  margin-top: 40px;
}

button {
  box-shadow: 10px 10px 20px rgba(0, 0, 0, 0.09);
}

.btn {
  padding: 7px 25px;
  font-size: 20px;
  margin: 0px 10px;
  color: white;
  border: none;
  cursor: pointer;
}

#start {
  background-color: green;
}
#stop {
  background-color: red;
}
#reset {
  background-color: yellowgreen;
}