main {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

.sticky-menu {
  width: 80%;
  height: 10%;
  min-height: 60px;
  max-width: 400px;
  background-color: var(--light-gray);
  border-radius: 0 0 12px 12px;
  z-index: 20;
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-start;
  align-items: center;
  align-content: space-around;
  padding: 1%;
}

.difficulty-btn,
.restart-btn {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 15%;
  height: 40%;
  border: none;
  border-radius: 10px;
  color: var(--light-gray);
  cursor: pointer;
  margin: 1% 2%;
  transition: all 0.2s ease;
}

button:hover {
  transform: scale(1.05);
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
  opacity: 0.9;
}

.restart-btn {
  justify-self: flex-end;
  margin-left: auto;
  background-color: #4f6d7a;
}

.progress-bar {
  order: 2;
  display: flex;
  align-items: center;
  justify-content: flex-start;
  width: 100%;
  height: 20px;
  background-color: #4f6d7a;
  border-radius: 10px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  position: relative;
  overflow: hidden;
}

.score {
  height: 100%;
  order: 4;
  background-color: var(--yellow);
  text-align: center;
  color: var(--light-gray);
  transition: width 0.3s ease;
  flex-grow: 0;
  flex-shrink: 0;
  padding: 2%;
}

#easy {
  background-color: var(--teal);
}

#medium {
  background-color: var(--yellow);
}

#hard {
  background-color: var(--dark-blue);
}

.card-container {
  margin: auto auto;
  width: 80%;
  height: 70%;
  max-width: 400px;
  background-color: var(--light-gray);
  border-radius: 5px;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  padding: 10px;
}

.card {
  background: linear-gradient(135deg, var(--dark-blue), var(--blue-collar));
  width: calc(90% / 4);
  border: 2px solid var(--yellow);
  transform-style: preserve-3d;
  transition: transform 0.4s ease-in-out;
}

.card.flipped {
  transform: rotateY(180deg);
}

.card:hover {
  background: var(--blue-collar);
}

.card.flipped {
  background: linear-gradient(45deg, var(--yellow), var(--teal));
}

.card.flipped.solved {
  background: var(--teal);
  opacity: 0.7;
  pointer-events: none;
}

.card-icon {
  font-size: 4em;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100%;
  visibility: hidden;
}

.show-icon {
  visibility: visible;
}

.timer {
  background-color: var(--light-gray);
  color: var(--dark-blue);
  padding: 12px 20px;
  border-radius: 12px;
  font-size: 28px;
  width: 100px;
  margin: 5px auto;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
  text-align: center;
}

.timer p {
  margin: 0;
  font-weight: bold;
}