@charset "utf-8";
@import url('https://fonts.googleapis.com/css2?family=Orbitron:wght@400;700&display=swap');
/* CSS 초기화 */
* {
  margin: 0px;
  padding: 0px;
}

ul,
ol {
  list-style: none;
}

a {
  outline: 0;
  text-decoration: none;
}

img {
  border: 0;
}

body {
  background: #efefef;
}

/* 화면 왼쪽에 고정 */
header {
  width: 400px;
  height: 100%;
  background: linear-gradient(45deg, aqua, royalblue);
  position: fixed;
  top: 0px;
  left: 0px;
}
header h1 {
  font: bold 50px/1 'orbitron';
  color: #fff;
  letter-spacing: 1px;
  position: absolute;
  left: 50px;
  top: 50%;
  transform: translateY(-150%);
}
header h1::before {
  content: 'UI/UX DEVELOPMENT';
  display: block;
  font: 14px/1 'orbitron';
  color: #fff;
  letter-spacing: 2px;
  position: absolute;
  left: 0;
  top: 90px;
  opacity: 0.8;
}
header h1::after {
  content: '';
  display: block;
  width: 150px;
  height: 2px;
  background: #fff;
  margin-top: 20px;
}
header ul {
  position: absolute;
  left: 40px;
  bottom: 100px;
}
header ul li {
  float: left;
  margin-right: 10px;
}
header ul li a {
  font-size: 20px;
  color: #fff;
}
/* 70프로 축소 하고 -10픽셀 만큼 이동
폰트 사이즈로 조절하지 않는 이유는 왼쪽 아이콘과 세로 정렬이 틀어지지 않게 하기 위함 */
header ul li a span {
  display: inline-block;
  font-weight: bold;
  opacity: 0.7;
  transform: scale(0.7) translateX(-10px);
}

/* 왼쪽 여백만 추가 */
main {
  margin-left: 400px;
  box-sizing: border-box;
  padding: 20px;
}

main ul {
  width: 100%;
  margin-bottom: 10px;
  margin-right: 20px;
}
main ul::after {
  content: '';
  display: block;
  clear: both;
}
main ul li {
  float: right;
  margin-right: 20px;
  width: 100px;
  height: 26px;
}
main ul li a {
  display: block;
  width: 100%;
  height: 100%;
  font: bold 7px/26px 'orbitron';
  color: #aaa;
  letter-spacing: 1px;
  text-align: center;
  border-radius: 5px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
  background: #fff;
}
main ul li.on a {
  background: linear-gradient(45deg, #67faf3, #58abf8);
  box-shadow: 0 5px 20px rgba(0, 255, 255, 0.527);
  color: #fff;
}

main section {
  width: 100%;
}
main section::after {
  content: '';
  display: block;
  clear: both;
}
main section article {
  width: 20%;
  float: left;
  box-sizing: border-box;
  padding: 12px;
}
main section article div {
  width: 100%;
  height: 100%;
  background: #fff;
  border-radius: 4px;
  box-shadow: 5px 5px 10px rgba(0, 0, 0, 0.1);
  box-sizing: border-box;
  padding: 4px;
}
main section article div img {
  width: 100%;
}
main section article div h2 {
  margin-top: 15px;
  font: bold 11px/1 'orbitron';
  letter-spacing: 1px;
  color: #444;
  margin-bottom: 5px;
}
main section article div p {
  font: 10px/1.2 'arial';
  color: #777;
  margin-bottom: 15px;
}

@media screen and (max-width: 1599px) {
  header {
    width: 350px;
  }
  main {
    margin-left: 350px;
  }
  main section article {
    width: 25%;
  }
}

@media screen and (max-width: 1199px) {
  header {
    width: 100%;
    height: 80px;
    position: relative;
  }
  header h1 {
    font: bold 24px/1 'orbitron';
    transform: translateY(-50%);
  }
  header h1::before,
  header h1::after {
    display: none;
  }
  header ul {
    left: 83%;
    bottom: 25px;
  }
  header ul li {
    margin-right: 20px;
  }
  header ul li a {
    font-size: 20px;
  }
  header ul li a span {
    display: none;
  }
  main {
    width: 100%;
    margin-left: 0;
  }
  main section article {
    width: 25%;
  }
}

@media screen and (max-width: 899px) {
  header ul {
    left: 80%;
  }
  main section article {
    width: 33.3%;
  }
}

@media screen and (max-width: 679px) {
  header ul {
    left: 70%;
  }
  main section article {
    width: 50%;
  }
}

@media screen and (max-width: 539px) {
  header ul {
    display: none;
  }
  main ul {
    margin-right: 0;
    box-sizing: border-box;
    padding: 0 13px;
  }
  main ul li {
    margin-right: 2%;
    width: 32%;
  }
  main ul li:nth-of-type(1) {
    margin-right: 0;
  }
  main section article {
    width: 100%;
  }
}