/* --- RESET & CHUẨN HÓA --- */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: #f8f9fa;
    color: #333;
    line-height: 1.6;
}

/* --- HEADER & DROPDOWN MENU (Chống conflict) --- */
.main-header {
    background-color: #0f4c81;
    color: #fff;
    position: sticky;
    top: 0;
    z-index: 9999;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 15px 20px;
}

.logo {
    font-size: 22px;
    font-weight: bold;
    letter-spacing: 1px;
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    color: white;
    font-size: 28px;
    cursor: pointer;
}

.menu-list {
    display: flex;
    list-style: none;
}

.menu-list > li {
    position: relative;
}

.nav-link {
    display: block;
    padding: 10px 20px;
    color: #e0e0e0;
    text-decoration: none;
    transition: all 0.3s ease;
}

.nav-link:hover, .menu-list > li:hover > .nav-link {
    color: #ffffff;
    background-color: rgba(255,255,255,0.1);
    border-radius: 4px;
}

/* Submenu ẩn mặc định */
.submenu {
    position: absolute;
    top: 100%;
    left: 0;
    background-color: #ffffff;
    min-width: 240px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.15);
    list-style: none;
    display: none;
    border-top: 3px solid #0f4c81;
}

.submenu li a {
    color: #333;
    padding: 12px 20px;
    display: block;
    text-decoration: none;
    font-size: 14px;
    transition: background 0.2s;
}

.submenu li a:hover {
    background-color: #f1f5f9;
    color: #0f4c81;
}

/* Hover hiện submenu trên Desktop */
@media (min-width: 769px) {
    .dropdown:hover .submenu {
        display: block;
    }
}

/* --- BANNER --- */
.main-banner {
    background: linear-gradient(rgba(15, 76, 129, 0.85), rgba(15, 76, 129, 0.7)), 
                url('https://picsum.photos/1920/600?id=weather') no-repeat center center/cover;
    color: white;
    text-align: center;
    padding: 100px 20px;
}

.banner-content max-width: 800px; margin: 0 auto; {
    font-size: 2.5rem;
    margin-bottom: 15px;
}

/* --- MAIN BODY: Đặt chính xác 75% chiều rộng --- */
.main-body {
    width: 75%;
    margin: 40px auto;
    min-height: 600px;
}

.section-title {
    font-size: 1.8rem;
    color: #0f4c81;
    margin-bottom: 25px;
    border-left: 5px solid #0f4c81;
    padding-left: 15px;
}

/* 1. CSS Tiêu biểu */
.featured-box {
    display: flex;
    background: #fff;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    margin-bottom: 50px;
}
.featured-img { flex: 1; }
.featured-img img { width: 100%; height: 100%; object-fit: cover; display: block; }
.featured-info { flex: 1; padding: 30px; display: flex; flex-direction: column; justify-content: center; }
.featured-info h3 { color: #222; margin-bottom: 15px; font-size: 1.4rem; }
.btn-detail { display: inline-block; margin-top: 15px; color: #0f4c81; text-decoration: none; font-weight: bold; }

/* 2. CSS Grid 3x2 (Mỗi box là 1 link động) */
.grid-container {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    margin-bottom: 50px;
}
.grid-box {
    background: #fff;
    padding: 25px;
    border-radius: 6px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.03);
    border: 1px solid #eef2f5;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
}
.grid-box:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(15, 76, 129, 0.1);
    border-color: #0f4c81;
}
.grid-box h3 { font-size: 1.1rem; color: #0f4c81; margin-bottom: 10px; }
.grid-box p { font-size: 0.9rem; color: #666; }

/* 3. CSS Công nghệ cốt lõi */
.core-list { list-style: none; }
.core-list li {
    display: flex;
    background: #fff;
    padding: 20px;
    border-radius: 6px;
    margin-bottom: 15px;
    align-items: center;
}
.core-list img { width: 80px; height: 80px; border-radius: 50%; margin-right: 20px; object-fit: cover;}
.core-text h4 { color: #222; font-size: 1.1rem; margin-bottom: 5px; }

/* --- FOOTER --- */
.main-footer {
    background: #222;
    color: #aaa;
    text-align: center;
    padding: 30px 20px;
    font-size: 0.9rem;
    margin-top: 60px;
}

/* --- RESPONSIVE CHO SMARTPHONE --- */
@media (max-width: 768px) {
    .menu-toggle { display: block; }
    .main-nav {
        display: none;
        width: 100%;
        position: absolute;
        top: 100%;
        left: 0;
        background-color: #0f4c81;
    }
    .main-nav.active { display: block; }
    .menu-list { flex-direction: column; }
    .submenu { position: static; box-shadow: none; background-color: #0d3f6c; border-top: none; }
    .submenu li a { color: #fff; padding-left: 40px; }
    
    /* Ép kích thước body về 90-95% trên mobile để dễ nhìn */
    .main-body { width: 92%; margin: 20px auto; }
    
    .featured-box { flex-direction: column; }
    .grid-container { grid-template-columns: 1fr; } /* Chuyển thành 1 cột trên mobile */
    .core-list li { flex-direction: column; text-align: center; }
    .core-list img { margin-right: 0; margin-bottom: 15px; }
}