* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body,
html {
  height: 100%;
  font-family: 'Arial', sans-serif;
  background-color: #34495e;
  color: #ecf0f1;
  display: flex;
  justify-content: center;
  align-items: center;
  overflow: hidden;
}

#game-container {
  text-align: center;
}

#start-screen {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

#start-screen h1 {
  font-size: 48px;
  color: #1abc9c;
  margin-bottom: 20px;
}

#level-selection {
  margin-bottom: 30px;
}

.level-btn {
  background-color: #16a085;
  color: white;
  font-size: 18px;
  padding: 12px 20px;
  border: none;
  border-radius: 8px;
  margin: 10px;
  cursor: pointer;
  transition: background-color 0.3s ease, transform 0.3s ease;
}

.level-btn:hover {
  background-color: #1abc9c;
  transform: scale(1.1);
}

#start-btn {
  background-color: #e74c3c;
  color: white;
  font-size: 20px;
  padding: 12px 24px;
  border: none;
  border-radius: 8px;
  margin-top: 20px;
  cursor: pointer;
  transition: background-color 0.3s ease, transform 0.3s ease;
}

#start-btn:hover {
  background-color: #c0392b;
  transform: scale(1.1);
}

#game-screen {
  display: grid;
  gap: 15px;
  max-width: 700px;
  margin: 0 auto;
  padding: 20px;
}

#timer-bar {
  width: 100%;
  height: 6px;
  background-color: #e74c3c;
  position: fixed;
  top: 0;
  left: 0;
}

#card-container {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 15px;
  justify-items: center;
  padding: 20px;
}

.card {
  width: 120px;
  height: 120px;
  perspective: 1000px;
  transition: transform 0.5s ease;
}

.card:hover {
  transform: scale(1.05);
}

.card .flipper {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.5s;
}

.front,
.back {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 24px;
  color: #ecf0f1;
  background: #2980b9;
  border-radius: 10px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
}

.front {
  background-image: url('https://via.placeholder.com/120');
  background-size: cover;
  background-position: center;
  font-size: 0;
  border-radius: 10px;
}

.back {
  background-color: #e74c3c;
  transform: rotateY(180deg);
  font-size: 32px;
}

.overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.7);
  display: flex;
  justify-content: center;
  align-items: center;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
}

.overlay.show {
  opacity: 1;
  pointer-events: all;
}

.overlay-content {
  background-color: #fff;
  color: #333;
  padding: 40px;
  border-radius: 10px;
  text-align: center;
  width: 300px;
  box-shadow: 0 8px 15px rgba(0, 0, 0, 0.3);
}

.overlay-content h2 {
  font-size: 26px;
  margin-bottom: 20px;
}

.overlay-content ul {
  list-style-type: none;
  padding: 0;
  margin-bottom: 20px;
}

.overlay-content li {
  margin: 10px 0;
}

button {
  background-color: #16a085;
  color: white;
  font-size: 18px;
  padding: 12px 20px;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background-color 0.3s ease, transform 0.3s ease;
  margin-top: 10px;
}

button:hover {
  background-color: #1abc9c;
  transform: scale(1.05);
}

button:focus {
  outline: none;
}

#card-container {
  display: grid;
  gap: 10px;
  justify-content: center;
  align-items: center;
  margin: 20px;
}

.card {
  width: 100px;
  height: 100px;
  perspective: 1000px;
  cursor: pointer;
  display: flex;
  justify-content: center;
  align-items: center;
  transform-style: preserve-3d;
  transition: transform 0.6s;
}

.card:hover {
  transform: scale(1.1);
}

.flipper {
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.6s;
}

.front,
.back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 24px;
  font-weight: bold;
}

.front {
  background-image: url('https://highseas.hackclub.com/highlogo.svg');
  background-size: contain;
  background-position: center;
  font-size: 0;
  border-radius: 10px;
}

.back {
  background-color: #4CAF50;
  color: white;
  font-size: 32px;
  transform: rotateY(180deg);
}

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