@charset "utf-8";

body {
  font-family: Arial, Helvetica, "微軟正黑體", sans-serif;
}

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

h1 {
  text-align: center;
  color: #70bbf9;
  margin: 1em;
  font-size: 3em;
}

.container {
  max-width: 900px;
}

.mx-auto {
  margin-left: auto;
  margin-right: auto;
}

.tab__nav {
  border-bottom: solid 1px #ccc;
}

.tab__btn {
  margin-bottom: -2px;
  padding: .7rem 1rem;
  font-size: 1rem;
  color: #bbb;
  border: 0;
  background-color: transparent;
}

.tab__btn:disabled {
  background-color: #eef9ff;
  color: #70bbf9;
  border-bottom: solid 4px #70bbf9;
}

.tab__item {
  display: none;
  padding-top: 1rem;
  padding-bottom: 1rem;
}

.tab__ul {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}

.tab__li {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100px;
  background-color: #eee;
}

.tab__li::before,
.tab__li::after {
  position: absolute;
  border: solid 15px transparent;
  content: "";
}

.tab__li::before {
  left: 0;
  top: -15px;
  border-left-color: #fff;
}

.tab__li::after {
  right: 0;
  bottom: -15px;
  border-right-color: #fff;
}