header {
    background-color: #0077cc;
    color: white;
    padding: 8px 16px;
}

header nav a {
    color: white;
    margin-right: 16px;
    text-decoration: none;
}

main {
    padding: 20px;
}

footer {
    text-align: center;
    padding: 8px;
    background-color: #f2f2f2;
}

body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f5f7fa;
    font-size: 32px;
    color: #111;
    text-align: center;
}

h1 {
    color: #222;
    margin: 20px 0 20px 0;
    font-size: 44px;
    font-weight: bold;
}

.lesson {
    background: #fff;
    margin: 0 auto;
    padding: 20px 20px 30px;
    border-radius: 16px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    width: 95%;
    max-width: 1200px;
}

.lesson strong {
    font-size: 40px;
    display: block;
    margin-bottom: 20px;
}

img {
    width: 86%;
    border-radius: 14px;
    margin-bottom: 16px;
    box-shadow: 0 4px 14px rgba(0,0,0,0.25);
    display: block;
    margin-left: auto;
    margin-right: auto;
}

button {
    cursor: pointer;
    padding: 20px 20px;
    margin: 12px 24px 12px 24px;
    font-size: 38px;
    border-radius: 12px;
    border: none;
    background-color: #306030;
    color: white;
    transition: 0.2s;
}

button:hover {
    background-color: #2A552A;
    transform: scale(1.05);
}

.nav-buttons button {
    background: white;
    color: #306030;
    border: 2px solid #306030;
    padding: 16px 24px;
    font-size: 38px;
    border-radius: 12px;
}

.nav-buttons button:hover {
    background-color: #e6f3e6;
    transform: scale(1.05);
}

.transcript {
    display: none;
    background: #f9f9f9;
    padding: 24px;
    border-left: 6px solid #007bff;
    margin-top: 16px;
    white-space: pre-line;
    font-size: 28px;
    line-height: 1.5;
    border-radius: 12px;
    text-align: left;
    width: 90%;
    margin-left: auto;
    margin-right: auto;
}

.correct-answer {
  color: green;
  font-weight: bold;
}

.wrong-answer {
  color: red;
  font-weight: bold;
}

.nav-buttons {
    margin-top: 18px;
}

.audio-wrapper {
    transform: scale(2.2);
    transform-origin: top center;
    width: fit-content;
    margin: 8px auto 80px auto;
}

.audio-wrapper audio {
    width: 356px;
}

.selected {
  background-color: #b3d9ff; /* xanh nhạt user chọn */
}

.correct {
  background-color: #c6f5c6; /* xanh lá nhạt đúng */
}

.wrong {
  background-color: #fff2b3; /* vàng nhạt sai */
}

.options {
    margin-top: 25px;
    width: 100%;
}

.option-row {
    display: flex;
    align-items: center;
    margin: 10px 0;
}

.option-btn {
    width: 60px;
    font-size: 36px;
    padding: 12px 0;
    margin-right: 16px;
    background:#306030;
    color:white;
    border:none;
    border-radius:10px;
}

.option-text {
    font-size: 32px;
    display: none;        /* ẨN MẶC ĐỊNH */
}