/* body of the page */

body {
  background-color: #eef9bf;
}

/* title header */

header {
  width: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
}

header h1 {
  font-family: "Roboto", sans-serif;
  font-weight: 700;
  font-size: 56px;
  line-height: 65.63px;
  color: #75b79e;
  display: flex;
  justify-content: center;
  align-items: center;
}

/* main container */

main {
  width: 100%;
  margin-top: 50px;
  display: flex;
  justify-content: center;
  align-items: center;
}

/* box of letters */

.box-cards {
  width: 1000px;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
}

.card {
  width: 117px;
  height: 146px;
  margin: 20px;
  position: relative;
  cursor: pointer;
}

.face {
  width: 100%;
  height: 100%;
  background-color: #a7e9af;
  border: 1px solid #99cea8;
  border-radius: 5px;
  box-shadow: 1px 1px 1px rgba(0, 0, 0, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
  position: absolute;
  backface-visibility: hidden;
  transition: all 0.5s;
  transform-style: preserve-3d;
}

.back-face {
  transform: rotateY(180deg);
}

.selected-back {
  transform: rotate(0deg);
}

.selected-front {
  transform: rotateY(-180deg);
}

/* image of cards */

.front-face img {
  height: 100px;
  margin: 10px;
}

.back-face img {
  height: 100px;
  margin: 10px;
}

/* clock layout */

.clock {
  color: #86BD8D;
  font-family: "Roboto", sans-serif;
  margin-right: 20px;
  margin-top: 20px;
  font-weight: 700;
  font-size: 36px;
  position: absolute;
}

/* watch container */

.container {
  height: 50px;
  display: flex;
  justify-content: right;
  align-items: center;
}

/* layout mobile */

@media (max-width: 600px) {

  header h1 {
    width: 312px;
    font-size: 36px;
    line-height: 42.19px;
    text-align: center;
    margin-top: 20px;
    margin-bottom: -40px;
  }

  .box-cards {
    flex-direction: column;
  }
}