* {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
}

.banner {
  width: 100%;
  height: 100vh;

  background: linear-gradient(rgba(0, 0, 0, 0.75), rgba(0, 0, 0, 0.75)),
    url(a.jpg);
  background-position: center;
  background-size: cover;
}

.nav {
  width: 85%;
  margin: auto;
  padding: 35px 0;
  display: flex;
  text-align: center;
  justify-content: space-between;
}

.logo {
  width: 60px;
  cursor: pointer;
}
.nav ul li {
  list-style-type: none;
  display: inline-block;
  margin: 10px 20px;
  position: relative;
}

.nav ul li a {
  text-decoration: none;
  color: white;
  text-transform: uppercase;
  font-size: larger;
}

.nav ul li::after {
  content: "";
  height: 3px;
  width: 0%;
  background: #009688;
  position: absolute;
  left: 0; /* means start from left*/
  bottom: -4px;
  transition: 0.3s;
}

.nav ul li:hover::after {
  width: 100%;
}

.content {
  width: 100%;
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  text-align: center;
  color: #fff;
}

.content h1 {
  font-size: 70px;
  margin-top: 0px;
}

.content p {
  margin: 20px auto;
  font-weight: 100;
  line-height: 25px;
}

button {
  text-align: center;
  background-color: transparent;
  width: 200px;
  font-size: large;
  color: white;

  border-radius: 40px;

  padding: 10px 0;
  margin: 0 5px;
  border: 1px solid #009688;
  font-weight: bold;
  outline: none;
  position: relative;

  overflow: hidden;
  cursor: pointer;
}

span {
  border-radius: 40px;
  height: 100%;
  width: 0;
  background-color: #009688;
  position: absolute;
  left: 0;
  bottom: 0;
  z-index: -1;
  transition: 0.5s;
}

button:hover span {
  width: 100%;
}
button:hover {
  border: none;
}