* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Orbitron', 'Roboto', sans-serif;
}

body {
  background: 
    linear-gradient(135deg, rgba(26, 26, 46, 0.85), rgba(15, 22, 38, 0.85)),
    url('images/neural-bg.png') no-repeat center center fixed;
  background-size: cover;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem;
  color: #fff;
  overflow-x: hidden;
}

.container {
  text-align: center;
  max-width: 650px;
  width: 100%;
  padding: 1rem;
}

h1 {
  font-size: 3rem;
  margin-bottom: 0.3rem;
  color: #f8f8f8;
  text-shadow: 0 0 10px #00ffe1, 0 0 20px #00ffe1aa;
}

.subtitle {
  font-size: 1.2rem;
  margin-bottom: 2rem;
  color: #ccc;
  font-weight: 300;
  text-shadow: 0 0 4px rgba(0, 255, 225, 0.3);
}

.button-group {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin-bottom: 2rem;
}

.btn-glow {
  padding: 0.8rem 1.6rem;
  background: rgba(255, 255, 255, 0.06);
  border: 1.5px solid #00ffe1;
  color: #fff;
  border-radius: 30px;
  font-size: 1rem;
  cursor: pointer;
  backdrop-filter: blur(6px);
  box-shadow: 0 0 12px #00ffe155;
  transition: all 0.3s ease;
}

.btn-glow:hover {
  background: rgba(0, 255, 225, 0.15);
  transform: translateY(-3px) scale(1.05);
  box-shadow: 0 0 25px #00ffe1cc;
}

.instructions {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(20, 20, 20, 0.9);
  backdrop-filter: blur(10px);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 99;
  padding: 1rem;
}

.hidden {
  display: none;
}

.glass-box {
  background: rgba(255, 255, 255, 0.06);
  border-radius: 20px;
  padding: 2rem;
  color: #fff;
  max-width: 400px;
  width: 100%;
  box-shadow: 0 0 25px #00ffe1;
  border: 1px solid rgba(255, 255, 255, 0.15);
  backdrop-filter: blur(12px);
}

.instructions h3 {
  margin-bottom: 1rem;
  font-size: 1.6rem;
}

.instructions ol {
  text-align: left;
  margin-bottom: 1.5rem;
  padding-left: 1rem;
}

.instructions li {
  margin-bottom: 0.7rem;
  font-weight: 300;
  font-size: 0.95rem;
}

.btn-container {
  margin-top: 2rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  align-items: center;
}

.line-one,
.line-two {
  display: flex;
  gap: 1.2rem;
}

.btn-tile {
  width: 130px;
  height: 130px;
  border-radius: 18px;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.3s ease;
  box-shadow: inset 0 0 15px rgba(255, 255, 255, 0.1), 0 5px 15px rgba(0, 0, 0, 0.4);
  position: relative;
  overflow: hidden;
  border: 2px solid #ffffff20;
}

.btn-tile:active,
.btn-tile.userflash,
.btn-tile.flash {
  transform: scale(1.08);
  box-shadow: 0 0 25px #ffffffaa, inset 0 0 30px #fff;
  border-color: #ffffff66;
}

.red {
  background: radial-gradient(circle at top left, #e74c3c, #c0392b);
}

.yellow {
  background: radial-gradient(circle at top left, #f1c40f, #f39c12);
}

.green {
  background: radial-gradient(circle at top left, #2ecc71, #27ae60);
}

.purple {
  background: radial-gradient(circle at top left, #9b59b6, #8e44ad);
}

/* Game over effect */
body.wrong-background {
  background: radial-gradient(circle, #ff0000, #7a0000);
  transition: background 0.5s ease;
}

@media screen and (max-width: 500px) {
  .btn-tile {
    width: 100px;
    height: 100px;
  }

  .btn-glow {
    font-size: 0.9rem;
    padding: 0.5rem 1.2rem;
  }

  h1 {
    font-size: 2.4rem;
  }

  .subtitle {
    font-size: 1rem;
  }
}