:root {
  --yellow: #efef9e;
  --red: #ffaaaa;
  --cyan: #9eefef;
  --blue: #00aaff;
  --gray: #cfcfcf;
  --green: #aaffaa;
}

body {
  margin: 0;
  font-family: Quicksand, sans-serif;
}

img {
  max-width: 100%;
}

h1, h2, p, ul {
  margin: 0;
}

p + p {
  margin-top: 20px;
}

header ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

header h1 {
  width: 100%;
  max-width: 800px;
  position: absolute;
  left: 0;
  top: 0;
  margin-left: 270px;
}

header nav ul li {
  border: 4px solid;
  width: max-content;
  padding: 10px 20px;
  margin: 20px 0 0 20px;
  cursor: pointer;
  user-select: none;
}

header nav ul li.active {
  background: black;
  color: white;
  border-color: black;
}

main section {
  max-width: 600px;
  border: 4px solid;
  padding: 20px;
  position: absolute;
  cursor: move;
  user-select: none;
}

main section.hidden {
  display: none;
}

section:nth-child(6n+1) {
  background: url(../png/bg_yellow.png);
  border-color: var(--yellow);
  top: 40px;
  left: 270px;
}

section:nth-child(6n+2) {
  background: url(../png/bg_red.png);
  border-color: var(--red);
  top: 60px;
  left: 290px;
}

section:nth-child(6n+3) {
  background: url(../png/bg_cyan.png);
  border-color: var(--cyan);
  top: 80px;
  left: 310px;
}

section:nth-child(6n+4) {
  background: url(../png/bg_blue.png);
  border-color: var(--blue);
  top: 100px;
  left: 330px;
}

section:nth-child(6n+5) {
  background: url(../png/bg_gray.png);
  border-color: var(--gray);
  top: 120px;
  left: 350px;
}

section:nth-child(6n+6) {
  background: url(../png/bg_green.png);
  border-color: var(--green);
  top: 140px;
  left: 370px;
}