/* Định kiểu cho toàn bộ trang */
body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f4;
    margin: 0;
    padding: 0;
}

header {
    background-color: #007bff;
    color: white;
    padding: 10px 0;
    border-radius: 0 0 15px 15px; 
    width: 100%; 
    display: flex;
    align-items: center; 
    justify-content: center;
}

header nav ul {
    list-style-type: none;
    padding: 0;
    text-align: center;
    display: flex;
    align-items: center;
}

header nav ul li {
    margin-right: 20px;
}

header nav ul li img.logo {
    height: 40px;
    width: auto;
    border-radius: 8px; 
    margin-right: 15px; 
}

header nav ul li a {
    color: white;
    text-decoration: none;
    font-size: 18px;
}

header nav ul li a:hover {
    text-decoration: underline;
}

main {
    padding: 20px;
    text-align: center;
}

h2 {
    font-size: 24px;
    margin-bottom: 20px;
}

.problem-block {
    background-color: white;
    padding: 20px;
    margin-bottom: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    text-align: left;
}

.problem-block h3 {
    font-size: 20px;
    color: #007bff;
}

.problem-block p {
    font-size: 16px;
    line-height: 1.5;
}

.submit-block {
    background-color: white;
    padding: 20px;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    text-align: left;
    margin-top: 30px;
}

.submit-block label {
    font-size: 16px;
    margin-bottom: 10px;
    display: block;
}

.submit-block textarea {
    width: 100%;
    padding: 10px;
    font-size: 16px;
    border-radius: 4px;
    border: 1px solid #ccc;
    margin-bottom: 10px;
}

.submit-block input {
    padding: 10px;
    font-size: 16px;
    width: 100%;
    margin-bottom: 10px;
    border-radius: 5px;
    border: 1px solid #ccc;
}

.submit-block button {
    padding: 10px 15px;
    font-size: 16px;
    background-color: #007bff;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

.submit-block button:hover {
    background-color: #0056b3;
}

footer {
    background-color: #007bff;
    color: white;
    text-align: center;
    padding: 15px 0;
    margin-top: 20px;
}

footer a {
    color: white;
    text-decoration: none;
}

footer a:hover {
    text-decoration: underline;
}

div {
    padding: 20px;
    margin: 20px auto;
    background-color: white;
    border-radius: 8px;
    width: 80%; 
    max-width: 900px; 
    transition: transform 0.3s ease, box-shadow 0.3s ease; 
}

div:hover {
    transform: translateY(-10px); 
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2); 
}

div h2 {
    color: #333;
}