:root{   margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}


body {
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: flex-start;

    background: url('img/nen6.jpg') center/cover no-repeat;
    color: #fff;
    position: relative;
}

body::before {
    content: "";
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.5); 
    z-index: 0;
}


body::after {
    content: "";
    position: fixed;
    top:0;
    left:0;
    width:100%;
    height:100%;
    pointer-events: none;
    background: radial-gradient(circle at center, rgba(255,255,255,0.08) 0%, rgba(0,0,0,0.6) 70%);
}

.container {
    margin-top: 70px;
    text-align: center;
    padding: 120px 60px;     
    background: rgba(0,0,0,0.6); 
    border-radius: 25px;     
    max-width: 700px;          
    width: 95%;               
    margin-bottom: 50px;
    color: #fff;
    box-shadow: 0 0 30px rgba(255,0,0,0.6), 0 20px 60px rgba(0,0,0,0.4);
    border: 2px solid rgba(255,0,0,0.6);
    position: relative;
}


h2 {
    font-family: 'Arial Black', sans-serif;
    color: #ffb347;
    margin-bottom: 30px;
    font-size: 2.2rem;          /* to hơn */
    text-shadow: 0 0 12px #ff4500, 0 0 25px #ff6347;
}


#question {
    font-size: 22px;            
    margin-bottom: 35px;
}


#answers button {
    display: block;
    width: 95%;                
    margin: 12px auto;
    padding: 18px 0;           
    font-size: 18px;          
    border-radius: 20px;       
}
#answers button:hover { 
    transform: translateY(-3px); 
    box-shadow: 0 0 20px rgba(255,78,80,0.9), 0 10px 20px rgba(0,0,0,0.15);
 } 
  #answers button.correct { 
    background: linear-gradient(45deg, #ffb347, #ffd700); 
    color: #000; box-shadow: 0 0 15px rgba(255,180,71,0.7); } 
#answers button.wrong { 
    background: linear-gradient(45deg, #800000, #c70039);  
    color: #fff; 
    box-shadow: 0 0 15px rgba(199,0,57,0.7); 
}

.back {
      display: inline-block;
    margin: 20px;
    padding: 10px 20px;
    background: #ffef9c;
    color: #333;
    text-decoration: none;
    border-radius: 12px;
    font-weight: 600;
    font-size: 1.2rem; 
    box-shadow: 0 6px 10px rgba(0,0,0,0.1);
    transition: all 0.3s ease;

}

.back:hover {
    text-shadow: 0 0 10px #f1a02e, 0 0 15px #ff4500;
}

.progress-container {
    width: 90%;
    height: 12px;
    background: #3b0000;
    border-radius: 12px;
    margin: 20px auto;
    overflow: hidden;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.2);
}

#progress {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, #e60000, #ff4500);
    transition: width 0.4s ease;
    border-radius: 12px;
}


.score-display {
    font-size: 16px;
    font-weight: bold;
    color: #ffb347;
    margin-top: 10px;
    text-shadow: 0 0 6px #ffb347;
}

#quiz-end-popup {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.65);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 999;
}

#quiz-end-popup .popup-box {
    background: linear-gradient(180deg, #1a0000, #3b0000);
    border-radius: 28px;
    padding: 45px 50px;
    max-width: 520px;
    width: 90%;
    text-align: center;
    border: 2px solid rgba(255, 183, 77, 0.8);
    box-shadow:
        0 0 25px rgba(255, 180, 71, 0.6),
        0 30px 80px rgba(0,0,0,0.6);
    animation: popupIn 0.5s ease;
}

#quiz-end-popup h2 {
    font-size: 2.2rem;
    color: #ffd700;
    margin-bottom: 15px;
    text-shadow: 0 0 12px rgba(255,215,0,0.9);
}

#quiz-end-popup p {
    font-size: 1.25rem;
    color: #fff3c4;
    margin-bottom: 30px;
    line-height: 1.6;
}

#quiz-end-popup button {
    padding: 14px 32px;
    border-radius: 18px;
    border: none;
    cursor: pointer;
    font-size: 1.1rem;
    font-weight: 600;
    background: linear-gradient(45deg, #ffb347, #ffd700);
    color: #3b0000;
    box-shadow: 0 0 18px rgba(255,180,71,0.7);
    transition: all 0.25s ease;
}

#quiz-end-popup button:hover {
    transform: translateY(-3px);
    box-shadow: 0 0 28px rgba(255,200,90,0.95);
}

@keyframes popupIn {
    from {
        opacity: 0;
        transform: scale(0.85) translateY(30px);
    }
    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}