*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  width: 100vw;
  min-height: 100vh;
  font-family: Arial, Helvetica, sans-serif;
  color: #333;
  background-color: #f7f6ff;
}

.container {
  padding: 0 50px;
  width: 100%;
  max-width: 1170px;
  margin: 0 auto;
}

h1 {
  padding: 5px 15px;
  font-size: 22px;
}

.sandbox {
  width: 100%;
  max-width: 1150px;
  text-align: center;
}

.game-title {
  margin: 24px;
  font-size: 24px;
}

.start__block {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 15px;
  margin: 0 auto;
  width: 100%;
}

/* My Custom Select */

.select-box {
  display: flex;
  flex-direction: column;
  width: 275px;
  text-align: left;
}

.select-box .options-container {
  width: 100%;
  max-height: 0;
  border-radius: 8px;
  color: #f5f6fa;
  background-color: #2f3640;
  opacity: 0;
  transition: all .4s;
  overflow: hidden;
  order: 1;
}

.selected {
  position: relative;
  margin: 8px 0;
  border-radius: 8px;
  color: #f5f6fa;
  background-color: #2f3640;
  order: 0;
}

.selected::after {
  position: absolute;
  right: 10px;
  top: 50%;
  content: '';
  height: 100%;
  width: 17px;
  background: url('../images/arrow.svg') no-repeat center;
  background-size: contain;
  transform: translateY(-50%);
  transition: all .4s;
}

.select-box .options-container--active {
  max-height: 140px;
  opacity: 1;
  overflow-y: scroll;
}

.select-box .options-container--active+.selected::after {
  transform: rotateX(180deg);
  top: 0;
}

.select-box .options-container::-webkit-scrollbar {
  width: 8px;
  border-radius: 0 8px 8px 0;
  background-color: #0d141f;
}

.select-box .options-container::-webkit-scrollbar-thumb {
  border-radius: 0 8px 8px 0;
  background-color: #525861;
}

.select-box .option,
.selected {
  padding: 12px 24px;
  cursor: pointer;
}

.select-box label {
  cursor: pointer;
}

.select-box .option .radio {
  display: none;
}

.select-box .option:active,
.select-box .option:focus {
  background-color: #414b57;
}

@media (min-width: 1025px) {

  .select-box .option:hover {
    background-color: #414b57;
  }

}

/* My custom radio */

.difficulty {
  margin-bottom: 25px;
  opacity: 0;
  visibility: hidden;
  transition: opacity .35s ease .4s;
}

.difficulty--active {
  opacity: 1;
  visibility: visible;
}

.difficulty__level {
  position: relative;
  padding-left: 20px;
  cursor: pointer;
}

.difficulty__level:not(:last-child) {
  margin-right: 15px;
}

.difficulty__level input[type="radio"] {
  display: none;
}

.difficulty__level input[type="radio"]+span::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 15px;
  height: 15px;
  border: 1px solid #525861;
  border-radius: 50%;
  transition: border-color .2s linear;
}

.difficulty__level input[type="radio"]:checked+span::before {
  border-color: #2f3640;
}

.difficulty__level input[type="radio"]+span::after {
  content: '';
  position: absolute;
  top: 5px;
  left: 5px;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background-color: #2f3640;
  opacity: 0;
  transition: opacity .2s linear;
}

.difficulty__level input[type="radio"]:checked+span::after {
  opacity: 1;
}

/* Buttons */

.btn {
  display: block;
  padding: 12px 24px;
  margin: 0 auto;
  border: 2px solid #2f3640;
  border-radius: 8px;
  font-size: 18px;
  color: #f5f6fa;
  background-color: #2f3640;
  cursor: pointer;
  transition: border-color .2s ease, color .2s ease, background-color .2s ease, box-shadow .2s ease, opacity .35s ease .4s;
}

.start__btn {
  margin: 8px 0;
  opacity: 0;
  visibility: hidden;
}

.start__btn:active,
.start__btn:focus {
  outline: none;
  color: #2f3640;
  background-color: #f5f6fa;
}

.start__btn--active {
  opacity: 1;
  visibility: visible;
}

.restart__btn {
  padding: 0;
  font-size: 0;
  border-color: #fe6246;
  background-color: #fe6246;
  opacity: 0;
  visibility: hidden;
}

.restart__btn:active,
.restart__btn:focus {
  outline: none;
  border-color: #fe6246;
  color: #2f3640;
  background-color: #f5f6fa;
}

.restart__btn--active {
  padding: 12px 24px;
  margin-bottom: 15px;
  font-size: 18px;
  opacity: 1;
  visibility: visible;
}

.new-game__btn {
  border: 2px solid #2f3640;
  color: #2f3640;
  background-color: #f5f6fa;
}

.new-game__btn:active,
.new-game__btn:focus {
  outline: none;
  border-color: #f5f6fa;
  color: #f5f6fa;
  background-color: #2f3640;
}

@media (min-width: 1025px) {

  .start__btn:hover {
    color: #2f3640;
    background-color: #f5f6fa;
    box-shadow: 0 0 10px #2f3640;
  }

  .restart__btn:hover {
    box-shadow: 0 0 15px #fe6246;
  }

  .new-game__btn:hover {
    border-color: #f5f6fa;
    color: #f5f6fa;
    background-color: #2f3640;
  }

}

/* Cards Field */

.cards-field {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  padding: 25px 0;
}

.scene {
  margin: 10px;
  width: 182px;
  height: 256px;
  perspective: 600px;
}

.card {
  display: block;
  width: 100%;
  height: 100%;
  position: relative;
  transition: transform 1s;
  transform-style: preserve-3d;
  transform-origin: center right;
  cursor: pointer;
}

.card__face {
  position: absolute;
  height: 100%;
  width: 100%;
  border-radius: 15px;
  font-size: 64px;
  line-height: 250px;
  transition: box-shadow .2s ease;
  backface-visibility: hidden;
}

.card__face--front {
  background: url('../images/card.png') no-repeat center;
  background-size: contain;
}

.card__face--back {
  background: #ffd930;
  transform: rotateY(180deg);
  transition: background-color .35s ease 1s;
}

.card__face--back.error {
  background: #fe6246;
  transition: background-color .1s ease;
}

.card.is-flipped {
  transform: translateX(-100%) rotateY(-180deg);
}

.card.matched .card__face--back {
  background: #9cff6e;
}

@media (min-width: 1025px) {

  .card:hover .card__face {
    box-shadow: 0 0 15px #333;
  }

}

/* Timer */

.timer {
  position: -webkit-sticky;
  position: sticky;
  top: 10px;
  padding: 5px;
  margin: 0 auto;
  margin-bottom: 15px;
  width: 215px;
  border-radius: 10px;
  font-size: 24px;
  font-weight: 600;
  color: #f5f6fa;
  background-color: rgba(47, 54, 64, .75);
  opacity: 1;
  transition: opacity .75s ease;
  z-index: 1;
}

.timer__hidden {
  margin-bottom: 0;
  font-size: 0;
  opacity: 0;
  visibility: hidden;
}

/* Модальное окно */

.popup {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: rgba(48, 55, 65, .5);
  overflow: auto;
  visibility: hidden;
  opacity: 0;
  transition: opacity .2s ease 1s;
  z-index: 1;
}

.popup--active {
  visibility: visible;
  opacity: 1;
}

.popup__content {
  position: absolute;
  top: 50%;
  left: 50%;
  padding: 35px 20px 50px;
  width: 75%;
  border: 3px solid #0d141f;
  border-radius: 15px;
  text-align: center;
  color: #f5f6fa;
  background-color: #303741;
  transform: translate(-50%, -50%);
}

.popup__close {
  position: absolute;
  top: 7px;
  right: 7px;
  padding: 0 7px;
  border: none;
  border-radius: 50%;
  font-size: 28px;
  font-weight: bold;
  color: #f5f6fa;
  background-color: #303741;
  transition: color .2s ease, background-color .2s ease;
  cursor: pointer;
}

.popup__close:active,
.popup__close:focus {
  outline: none;
  color: #303741;
  background-color: #f5f6fa;
}

.game-title--finish {
  padding: 0;
  margin: 16px 0 30px;
}

@media (min-width: 1025px) {

  .popup__close:hover {
    color: #303741;
    background-color: #f5f6fa;
  }

}

/* Media Queries */

@media (max-width: 1024px) {
  .container {
    padding: 0 15px;
  }
}

@media (max-width: 768px) {
  .scene {
    width: 117px;
    height: 165px;
    perspective: 250px;
  }

  .card__face {
    border-radius: 10px;
    line-height: 165px;
  }
}

@media (max-width: 375px) {

  .difficulty__block {
    display: flex;
    flex-direction: column;
    align-items: center;
  }

  .difficulty__level:not(:last-child) {
    margin-bottom: 7px;
    margin-right: 0;
  }

}