/* Cấu hình cơ bản */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    display: flex;
    flex-direction: column; /* Đặt body theo cấu trúc cột */
    min-height: 100vh; /* Đảm bảo chiều cao tối thiểu là 100% chiều cao màn hình */
    font-family: 'Poppins', sans-serif;
    line-height: 1.6;
    color: #d1d1d1;
    background-color: #121212;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: auto;
}

/* Header */
header {
    background: linear-gradient(135deg, #212121, #333333);
    color: white;
    padding: 60px 0;
    text-align: center;
}

header h1 {
    font-size: 3rem;
    margin-bottom: 10px;
}

header .tagline {
    font-size: 1.2rem;
    font-weight: 300;
    color: #d1d1d1;
}

/* Navbar */
nav {
    background-color: #333;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
    position: sticky; /* Giữ cố định navbar khi cuộn */
    top: 0;
    z-index: 1000;
}

nav ul {
    display: flex;
    justify-content: center;
    align-items: center;
    list-style: none;
    padding: 10px 0;
    margin: 0;
}

nav ul li {
    margin: 0 15px;
}

nav ul li a {
    color: #d1d1d1;
    text-decoration: none;
    font-size: 1.1rem;
    font-weight: 500;
    padding: 10px 20px;
    border-radius: 30px;
    transition: all 0.3s ease-in-out;
    position: relative;
    z-index: 1;
}

nav ul li a:hover {
    color: #fff;
    background-color: #4CAF50;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
}

nav ul li a::before {
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    background-color: rgba(255, 255, 255, 0.1);
    border-radius: 30px;
    z-index: -1;
    transition: transform 0.3s ease-in-out;
    transform: scale(0.5);
    opacity: 0;
}

nav ul li a:hover::before {
    transform: scale(1);
    opacity: 1;
}

nav ul li a.active {
    color: #fff;
    background-color: #4CAF50;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
}

/* Section */
section {
    padding: 60px 0;
    flex: 1; /* Đẩy footer xuống dưới */
}

#about {
    background-color: #1f1f1f;
    text-align: left;
}

#about .card {
    background-color: #2c2c2c;
    padding: 30px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.5);
    border-radius: 10px;
    margin-top: auto;
    max-width: 800px;
}

.profile-img {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    object-fit: cover;
    border: 2px solid #ddd;
}

#about h2 {
    margin-bottom: 20px;
    color: #4CAF50;
}

/* Skills */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
    margin-top: 40px;
}

.skill-card {
    background-color: #2c2c2c;
    padding: 30px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.5);
    border-radius: 10px;
    text-align: left;
}

.skill-card h3 {
    margin-bottom: 10px;
    color: #4CAF50;
}

/* Labs */
#labs {
    background-color: #1f1f1f;
    padding: 20px;
    border-radius: 10px;
}

#labs h2 {
    color: #4CAF50;
    text-align: center;
    margin-bottom: 20px;
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 20px;
}

.card {
    background-color: #2a2a2a;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    text-align: center;
    transition: transform 0.3s ease, background-color 0.3s ease;
}

.card a {
    color: #4CAF50;
    text-decoration: none;
    font-weight: 600;
    font-family: 'Poppins', sans-serif;
}

.card:hover {
    background-color: rgba(255, 255, 255, 0.1);
    transform: translateY(-5px);
}

/* Footer */
footer {
    background-color: #1f1f1f;
    color: #d1d1d1;
    padding: 20px 0;
    text-align: center;
    width: 100%;
}