style.css

body {
  font-family: sans-serif;
  text-align: center;
  background: linear-gradient(to right, #a8ff78, #78ffd6);
  color: white;
}

.pop-image {
  position: absolute;
}

h2 {
  font-weight: 500;
  font-size: 30px;
}

.screen {
  width:100%;
  height:100vh;
  display: none;
}

#menu {
  display: block;
  font-size: 40px;
  display: flex;
  align-items: center;
  justify-content: space-around;
}


.menu-button {
  transform: scale(1);
  transition: transform 200ms ease-in;
  cursor: pointer;
}

.menu-button:hover{
  transform: scale(1.2);
}

#exercise {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.button {
  padding: 8px 16px;
  border-radius: 9px;
  text-decoration: none;
  background-color: pink;
  color: white;
  font-size: 30px;
  display: none;
  margin-top: 100px;
}

.button:hover {
  background-color: white;
  color:pink;
}

#timer {
  display: none;
  position:absolute;
  margin:0;
  top:30px;
  right:40px;
}

#countdown {
  display: none;
  font-size: 100px;
}