style.css

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

body {
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background-color: #121826;
  color: white;
  font-family: sans-serif;
}

h1 {
  margin-bottom: 20px;
}

/* The Game Board Container */
.memory-game {
  width: 640px;
  height: 480px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 15px;
  /* Perspective gives the 3D flip a realistic depth effect */
  perspective: 1000px; 
}

/* Individual Card Setup */
.memory-card {
  position: relative;
  border-radius: 8px;
  cursor: pointer;
  /* Allows the front and back to share the 3D space */
  transform-style: preserve-3d;
  /* Smooth animation for the flip */
  transition: transform 0.5s ease-in-out;
}

/* Clicking down on a card makes it slightly smaller for a physical feel */
.memory-card:active {
  transform: scale(0.97);
  transition: transform 0.2s;
}

/* Both faces of the card */
.front-face,
.back-face {
  width: 100%;
  height: 100%;
  position: absolute;
  border-radius: 8px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 3rem;
  /* Hides the "back" of the element when it rotates away from the camera */
  backface-visibility: hidden;
  box-shadow: 0 4px 8px rgba(0,0,0,0.3);
}

/* The Front (Emoji) - initially flipped away from the user */
.front-face {
  background-color: #ffffff;
  transform: rotateY(180deg);
}

/* The Back (Star) - facing the user initially */
.back-face {
  background-color: #4f46e5;
}

/* 
  The Flip Class 
  Your JavaScript will add this class to a card when clicked.
  It rotates the whole card 180 degrees, revealing the front-face.
*/
.memory-card.flip {
  transform: rotateY(180deg);
}