/* =========================================
   HỆ THỐNG BIẾN MÀU SẮC (CSS VARIABLES)
   Đồng bộ với Smart School mẹ nhưng tối ưu cho Smart Grade
   ========================================= */
:root {
    --bg-deep: #f0fdfa; /* Nền xanh mint cực nhạt */
    --bg-card: rgba(255, 255, 255, 0.95); 
    --border-tech: rgba(8, 145, 178, 0.3); /* Viền xanh công nghệ */
    
    --primary-neon: #0891b2; /* Xanh biển đậm (Chủ đạo) */
    --primary-neon-hover: #0e7490;
    
    --accent-lime: #84CC16; /* Xanh lá đọt chuối (Nhấn mạnh) */
    --accent-lime-hover: #65A30D;
    
    --text-glow: #083344; /* Chữ tiêu đề tối */
    --text-dim: #334155; /* Chữ nội dung xám */
    
    --danger: #ef4444; /* Đỏ báo lỗi/xóa */
}

/* =========================================
   CÀI ĐẶT CƠ BẢN TOÀN CỤC
   ========================================= */
html, body {
    min-height: 100%;
    margin: 0;
    padding: 0;
    font-family: 'Inter', 'Segoe UI', sans-serif;
    color: var(--text-glow);
    background-color: var(--bg-deep);
    overflow-x: hidden;
}

body {
    background-image:
        linear-gradient(rgba(8, 145, 178, 0.015) 1px, transparent 1px),
        linear-gradient(90deg, rgba(8, 145, 178, 0.015) 1px, transparent 1px),
        linear-gradient(rgba(8, 145, 178, 0.015) 1px, transparent 1px),
        linear-gradient(90deg, rgba(8, 145, 178, 0.015) 1px, transparent 1px);
    background-size: 100px 100px, 100px 100px, 200px 200px, 200px 200px;
    background-attachment: fixed;
}

/* UI COMPONENTS */
.btn-primary-neon {
    background-color: var(--primary-neon);
    color: white;
    font-weight: 600;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px -1px rgba(8, 145, 178, 0.1);
}

.btn-accent-lime {
    background-color: var(--accent-lime);
    color: white;
    font-weight: bold;
    padding: 0.75rem 1.5rem;
    border-radius: 0.75rem;
    transition: all 0.3s ease;
}

.glass-card {
    background: var(--bg-card);
    backdrop-filter: blur(12px);
    border: 1px solid var(--border-tech);
    border-radius: 1rem;
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.04);
}

/* HEADER & BANNERS */
.logo-box-tight {
    padding: 0 !important;
    overflow: hidden;
    filter: drop-shadow(4px 0 12px rgba(8, 145, 178, 0.15));
}

.logo-box-tight img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.banner-gradient {
    background: linear-gradient(135deg, #1e3a8a 0%, #1e40af 50%, #1d4ed8 100%);
    position: relative;
    overflow: hidden;
    transition: background-image 1.5s ease-in-out;
    background-size: cover;
    background-position: center;
}

.banner-gradient::after {
    content: '';
    position: absolute;
    inset: 0;
    background: rgba(15, 23, 42, 0.5); 
    z-index: 1;
}

.title-3d-glow {
    font-family: 'Montserrat', sans-serif;
    font-weight: 900;
    color: #ffffff;
    text-transform: uppercase;
    letter-spacing: 2px;
    text-shadow: 2px 2px 8px rgba(0,0,0,0.6);
    position: relative;
    z-index: 10;
}

/* MENU DROPDOWN */
.nav-container {
    background: #ffffff;
    position: relative; 
    z-index: 1001 !important;
    overflow: visible !important;
}

.dropdown-group { position: relative; display: inline-block; }
.dropdown-group > button {
    padding: 0.5rem 1rem;
    font-weight: 700;
    color: #1e3a8a;
    display: flex;
    align-items: center;
    border: none; background: none; cursor: pointer;
}

.dropdown-menu {
    display: none;
    position: absolute;
    left: 0; top: 100%;
    background-color: #ffffff;
    min-width: 250px;
    z-index: 9999 !important; 
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    border: 1px solid #e0f2fe;
    border-radius: 0 0 0.75rem 0.75rem;
}

.dropdown-group:hover .dropdown-menu { display: block; }

.dropdown-item {
    display: block;
    padding: 0.75rem 1.25rem;
    color: var(--text-dim);
    text-decoration: none;
    border-bottom: 1px solid #f8fafc;
}

.dropdown-item:hover {
    background-color: #f0f9ff;
    color: var(--primary-neon);
    border-left: 4px solid var(--primary-neon);
}

/* PEDAGOGICAL ARTICLE */
.pedagogical-article { line-height: 1.8; text-align: justify; }
.pedagogical-article p { text-indent: 30px; margin-bottom: 1.25rem; }
.section-title {
    font-size: 1.5rem; font-weight: 700;
    display: flex; align-items: center;
    margin-top: 2rem; border-bottom: 1px solid var(--border-tech);
}
.section-title i { width: 35px; }
.article-abstract {
    font-style: italic; font-size: 1.1rem; color: #64748b;
    border-bottom: 2px dashed #e2e8f0; padding-bottom: 1.5rem; margin-bottom: 2rem;
}