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

body {
  font-family: 'Poppins', sans-serif;
  text-align: center;
  background: radial-gradient(circle at center, #0b0b0b, #000);
  color: #fff;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  padding: 20px;
  position: relative;
  overflow-x: hidden;
}

/* Matrix Rain Background */
#matrix-bg {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  background: black;
  pointer-events: none;
}

h1 {
  font-size: 2.5rem;
  color: #00ff88;
  margin-top: 20px;
  margin-bottom: 20px;
  text-shadow: 0 0 15px #00ff88;
}

.mode-selection {
  margin: 20px 0;
}

.mode-button {
  padding: 12px 25px;
  margin: 10px;
  border: none;
  border-radius: 12px;
  background: linear-gradient(135deg, #00ff88, #00cc66);
  color: #000;
  cursor: pointer;
  font-size: 1.1rem;
  font-weight: bold;
  box-shadow: 0 0 10px #00ff88;
  transition: all 0.3s;
}

.mode-button:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #00ff88;
}

.player-input {
  display: none;
  margin: 20px 0;
  padding: 20px;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 12px;
  box-shadow: 0 0 10px rgba(0, 255, 136, 0.3);
}

.player-input h3 {
  color: #00ff88;
  margin-bottom: 15px;
}

.player-input input {
  padding: 10px 15px;
  margin: 10px;
  border: 1px solid #00ff88;
  border-radius: 8px;
  background: rgba(0, 0, 0, 0.5);
  color: white;
  font-size: 1rem;
  width: 200px;
}

.player-input button {
  margin-top: 10px;
  padding: 10px 20px;
  border: none;
  border-radius: 8px;
  background: linear-gradient(135deg, #00ff88, #00cc66);
  color: #000;
  cursor: pointer;
  font-size: 1rem;
  font-weight: bold;
  box-shadow: 0 0 10px #00ff88;
  transition: all 0.3s;
}

.player-input button:hover {
  transform: scale(1.05);
  box-shadow: 0 0 15px #00ff88;
}

.game-container {
  display: none;
  justify-content: center;
  align-items: center;
  margin-top: 20px;
}

.game-board {
  display: grid;
  grid-template-columns: repeat(3, minmax(90px, 120px));
  grid-template-rows: repeat(3, minmax(90px, 120px));
  gap: 8px;
  background-color: #1a1a1a;
  padding: 10px;
  border-radius: 16px;
  box-shadow: 0 0 25px #00ff88;
}

.cell {
  border: 2px solid #00ff88;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 2.5rem;
  cursor: pointer;
  border-radius: 10px;
  background-color: #0f0f0f;
  transition: all 0.2s;
}

.cell:hover {
  background-color: #004d26;
}

.game-info {
  display: none;
  margin-top: 25px;
}

p#turn {
  font-size: 1.3rem;
  color: #00ffcc;
  margin-bottom: 10px;
}

button {
  margin: 8px;
  padding: 12px 24px;
  border: none;
  border-radius: 10px;
  background: linear-gradient(135deg, #00ff88, #00cc66);
  color: #000;
  cursor: pointer;
  font-size: 1rem;
  font-weight: bold;
  box-shadow: 0 0 10px #00ff88;
  transition: all 0.3s;
}

button:hover {
  transform: scale(1.05);
  box-shadow: 0 0 20px #00ff88;
}

#winner-message {
  color: #ff4444;
  font-size: 2rem;
  margin-top: 30px;
  display: none;
  text-shadow: 0 0 10px #ff4444;
}

/* Player info display */
.player-info {
  display: none;
  margin-bottom: 20px;
  font-size: 1.2rem;
}

.player-x {
  color: #00ff88;
}

.player-o {
  color: #00ccff;
}

/* 📱 RESPONSIVE STYLING */
@media (max-width: 768px) {
  h1 {
    font-size: 2rem;
  }

  .game-board {
    grid-template-columns: repeat(3, minmax(80px, 100px));
    grid-template-rows: repeat(3, minmax(80px, 100px));
    gap: 6px;
  }

  .cell {
    font-size: 2rem;
  }

  .mode-button, button {
    width: 80%;
    font-size: 1rem;
  }

  #winner-message {
    font-size: 1.8rem;
  }
}

@media (max-width: 480px) {
  h1 {
    font-size: 1.8rem;
  }

  .game-board {
    grid-template-columns: repeat(3, minmax(70px, 90px));
    grid-template-rows: repeat(3, minmax(70px, 90px));
  }

  .cell {
    font-size: 1.8rem;
  }

  .mode-button, button {
    width: 90%;
    font-size: 1rem;
  }

  #winner-message {
    font-size: 1.5rem;
  }
}

/* Footer */
footer {
  background-color: #0b0b0b;
  padding: 3rem 2rem 1rem;
  margin-top: 40px;
  width: 100%;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 2rem;
}

.footer-column h3 {
  color: #00ff88;
  margin-bottom: 1.5rem;
  font-size: 1.3rem;
}

.footer-column ul {
  list-style: none;
}

.footer-column ul li {
  margin-bottom: 0.8rem;
}

.footer-column a {
  color: #ccc;
  text-decoration: none;
  transition: color 0.3s;
}

.footer-column a:hover {
  color: #00ff88;
}

.social-icons {
  display: flex;
  gap: 1rem;
  margin-top: 1rem;
}

.social-icons a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 50%;
  transition: all 0.3s;
}

.social-icons a:hover {
  background: #00ff88;
  transform: translateY(-3px);
}