* {
  margin: 0;
  padding: 0;
  list-style: none;
  box-sizing: border-box;
}
body {
  text-align: center;
}
#container {
    width: 90%;
    height: 400px;
    border-radius: 10px;
    margin: 50px auto;
  }
#main {
  width: 100%;
  height: 400px;
  margin: 0 auto;
  border: 1px solid #ccc;
  position: relative;
}

#main span:nth-child(1) {
  /* display: block; */
  color: #ccc;
  position: absolute;
  top: 5%;
  right: 5%;
}
#main span#screen {
  display: block;
  height: 50px;
  line-height: 50px;
  box-sizing: border-box;
  font-size: 30px;
  margin-right: 10px;
  position: absolute;
  top: 15%;
  right: 5%;
}
#main input {
  width: 90%;
  height: 50px;
  border: 1px solid #ccc;
  border-radius: 5px;
  position: absolute;
  top: 15%;
  left: 5%;
}
#main ul {
  width: 90%;
  height: 250px;
  position: absolute;
  /* border: 1px solid #ccc; */
  bottom: 5%;
  left: 5%;
}
#main ul li.left {
  margin-right: -4%;
}
#main ul li {
  float: left;
  width: 22%;
  height: 40px;
  margin-right: 4%;
  margin-bottom: 12.5px;
  box-sizing: border-box;
  border-radius: 2px;
  background-color: #f8f8f8;
  border: 1px solid #c6c6c6;
  /* text-align: center; */
  line-height: 40px;
  cursor: pointer;
  transition: all 0.5s;
  user-select: none;
}
#main ul li.submit {
  color: #fff;
  font-weight: bolder;
  background-color: #4d90fe;
  border: 1px solid #2f5bb7;
}
#main ul li.features {
  font-weight: bolder;
  background-color: #d6d6d6;
  border: 1px solid #c6c6c6;
}
#main ul li:hover {
  border-color: #a6a6a6;
}

@media (min-width: 576px) {
  #container {
    width: 70%;
    height: 400px;
    border-radius: 10px;
    margin: 50px auto;
  }
}

@media (min-width: 768px) {
  #container {
    width: 60%;
    height: 400px;
    border-radius: 10px;
    margin: 50px auto;
  }
}

@media (min-width: 992px) {
  #container {
    width: 50%;
    height: 400px;
    border-radius: 10px;
    margin: 50px auto;
  }
}

@media (min-width: 1200px) {
  #container {
    width: 40%;
    height: 400px;
    border-radius: 10px;
    margin: 50px auto;
  }
}

@media (min-width: 1400px) {
  #container {
    width: 30%;
    height: 400px;
    border-radius: 10px;
    margin: 50px auto;
  }
}