* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family:Arial, Helvetica, sans-serif
  }
  
body {
  background-color: #222; 
  margin: 0;  
  overflow:hidden;
    }
    
.app {
  background: #fff;
  width: 90%;
  max-width:600px;
  margin: 50px auto 0;
  border-radius: 50px;
  padding: 30px;       
}

.app h1 {
  font-weight: 25px;
  color: #000000;
  font-weight: 600;
  border-bottom: 5px solid #333;
  padding-bottom: 30px;
}

.quiz {
  padding: 20px 0;
}

.quiz h2 {
  font-size: 18px;
  color: #000000;
  font-weight: 600;
}

.btn {
  background: #fff;
  color: #222;
  font-weight: 500;
  width: 100%;
  border: 1px solid #222;
  padding: 10px;
  margin: 10px 0;
  text-align: left; 
  border-radius: 50px;
  cursor: pointer; 
  transition: all 0.7s;
}

.btn:hover {
  background: #222;
  color: #fff;
}

#next-btn {
  background: #000000;
  color: #fff;
  font-weight: 500;
  width: 150px; 
  border: 0;
  padding: 10px;
  margin: 20px auto 0;
  border-radius: 50px;
  cursor: pointer;
  
}
    
nav {
  background-color: #222;
  padding: 1rem 2rem;
  display: flex;
  justify-content: flex-end;
     
}
    
nav a {
  color: rgb(255, 255, 255);
  text-decoration: none;
  margin: 0 20px;
  position: relative;
  padding: 5px 0;
  transition: color 0.3s ease;
  font-size: 22px;
  font-family:Verdana, Geneva, Tahoma, sans-serif
}
    
nav a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  height: 2px;
  width: 100%;
  background-color: #ffffff;
  transform: scaleX(0);
  transform-origin: center;
  transition: transform 0.3s ease;
}
    
nav a:hover {
  color: #ffffff;
}
    
nav a:hover::after {
  transform: scaleX(1);
  transform-origin: center;
}

.cover {
  position: fixed;
  top: 4.3rem;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  overflow: hidden;
  pointer-events: none;
  fill: #414141;
  stroke-width: 0.5px;
  display: left;
  stroke: #000000;
      }



.correct{
  background:#9aeabc;
}
.incorrect{
  background: #ff0000
}