*{
    margin : 0;
    padding: 0;
    box-sizing: border-box;    /*it maintains better intendation that content-box */
}
body{
    font-family: 'Orbitron', monospace;
    text-align: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #1e3c72 0%, #2a5298 50%, #ff6b6b 100%);
    background-attachment: fixed;
    overflow-x: hidden;
    position: relative;
}

body::before{
    content: '';
    position: fixed;
    top: 0;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(circle at 25% 25%, rgba(255, 255, 255, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 75% 75%, rgba(255, 255, 255, 0.1) 0%, transparent 50%);
    animation: float 20s ease-in-out infinite;
    pointer-events: none;
    z-index: -1;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) rotate(0deg); }
    33% { transform: translate(30px, -30px) rotate(120deg); }
    66% { transform: translate(-20px, 20px) rotate(240deg); }
}

.game-container{
    padding: 2rem;
    position: relative;
    z-index: 1;
}

h1{
    font-size: 3.5rem;
    font-weight: 900;
    color: #fff;
    text-shadow: 0 0 20px rgba(255, 255, 255, 0.5);
    margin-bottom: 1rem;
    letter-spacing: 3px;
    animation: glow 2s ease-in-out infinite alternate;
}

@keyframes glow {
    from { text-shadow: 0 0 20px rgba(255, 255, 255, 0.5); }
    to { text-shadow: 0 0 30px rgba(255, 255, 255, 0.8), 0 0 40px rgba(255, 255, 255, 0.3); }
}

h2{
    font-size: 1.5rem;
    color: #fff;
    margin-bottom: 2rem;
    font-weight: 400;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

#start-btn {
  padding: 15px 30px;
  font-size: 1.2rem;
  border: none;
  background-color: #4CAF50;
  color: white;
  border-radius: 10px;
  margin: 20px auto;
  display: block;
  cursor: pointer;
  transition: background-color 0.3s;
}

#start-btn:hover {
  background-color: #45a049;
}


.score-container{
    display: flex;
    justify-content: center;
    gap: 3rem;
    margin-bottom: 2rem;
}

.score-box{
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border: 2px solid rgba(255, 255, 255, 0.2);
    border-radius: 15px;
    padding: 1rem 2rem;
    color: #fff;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
}
.score-label{
    font-size: 0.9rem;
    opacity: 0.8;
    margin-bottom: 0.5rem;
}

.score-value{
    font-size: 2rem;
    font-weight: 900;
}

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

.line-one , .line-two{
    display: flex;
    gap: 1rem;
}

.btn {
    height: 180px;
    width: 180px;
    border-radius: 50%;
    border: 6px solid rgba(255, 255, 255, 0.3);
    cursor: pointer;
    font-size: 3rem;
    font-weight: 900;
    color: rgba(255, 255, 255, 0.9);
    display: flex;
    align-items: center;
    justify-content: center;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.5);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 
        0 10px 25px rgba(0, 0, 0, 0.3),
        inset 0 2px 5px rgba(255, 255, 255, 0.2);
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    transform: translate(-50%, -50%);
    transition: all 0.5s ease;
}

.btn:hover {
    transform: translateY(-5px) scale(1.05);
    box-shadow: 
        0 15px 35px rgba(0, 0, 0, 0.4),
        inset 0 2px 5px rgba(255, 255, 255, 0.3);
}

.btn:hover::before {
    width: 100%;
    height: 100%;
}

.btn:active {
    transform: translateY(-2px) scale(0.98);
}

.yellow{
    background: linear-gradient(135deg, #ffd93d, #f39c12);
}

.red{
    background: linear-gradient(135deg, #ff6b6b, #ee5a52);
}

.purple{
   background: linear-gradient(135deg, #9b59b6, #8e44ad);
}

.green{
   background: linear-gradient(135deg, #2ecc71, #27ae60);
}

.flash {
    background: #fff !important;
    box-shadow: 
        0 0 30px rgba(255, 255, 255, 0.8),
        0 10px 25px rgba(0, 0, 0, 0.3) !important;
    transform: scale(1.1) !important;
}

.userFlash {
    background: #00ff88 !important;
    box-shadow: 
        0 0 30px rgba(0, 255, 136, 0.8),
        0 10px 25px rgba(0, 0, 0, 0.3) !important;
    transform: scale(1.1) !important;
}

.game-over {
    background: linear-gradient(135deg, #ff4757, #c44569) !important;
    animation: shake 0.5s ease-in-out;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-10px); }
    75% { transform: translateX(10px); }
}

.instructions {
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border-radius: 15px;
    padding: 1.5rem;
    margin: 2rem auto;
    max-width: 600px;
    color: #fff;
    border: 2px solid rgba(255, 255, 255, 0.2);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
}

.instructions h3 {
    margin-bottom: 1rem;
    font-size: 1.3rem;
    color: #ffd93d;
}

.instructions p {
    line-height: 1.6;
    opacity: 0.9;
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    h1 {
        font-size: 2.5rem;
    }
    
    .btn {
        height: 140px;
        width: 140px;
        font-size: 2rem;
    }
    
    .score-container {
        gap: 1.5rem;
    }
    
    .score-box {
        padding: 0.8rem 1.5rem;
    }
    
    .score-value {
        font-size: 1.5rem;
    }
}

@media (max-width: 480px) {
    .line-one, .line-two {
        gap: 0.5rem;
    }
    
    .btn {
        height: 120px;
        width: 120px;
        font-size: 1.5rem;
    }
}