/* ==========================================================================
   1. BIẾN MÔI TRƯỜNG & TĂNG TỐC PHẦN CỨNG GPU (HARDWARE ACCELERATION)
   ========================================================================== */
:root {
    --deep-teal: #005f73;
    --electric-cyan: #00f5ff;
    --bg-light: #f0f7f9;
    --glass-bg: rgba(240, 247, 249, 0.78);
    --glass-border: rgba(0, 95, 115, 0.22);
    --text-main: #1d2d31;
    --text-muted: #527982;
    --font-primary: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --shadow-deep: 0 25px 50px rgba(0, 95, 115, 0.08), 0 1px 0px rgba(255, 255, 255, 0.7) inset;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-primary);
    background-color: var(--bg-light);
    color: var(--text-main);
    line-height: 1.7;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

.gpu-render {
    will-change: transform, opacity;
    transform: translateZ(0);
}

/* ==========================================================================
   2. TYPOGRAPHY UI/UX HIỆN ĐẠI
   ========================================================================== */
h1, h2, h3, h4 {
    color: var(--deep-teal);
    font-weight: 700;
    line-height: 1.3;
    margin-bottom: 1.2rem;
}
h1 { font-size: 2.6rem; }
h2 { font-size: 1.9rem; border-left: 6px solid var(--electric-cyan); padding-left: 18px; margin-top: 2.5rem; }
h3 { font-size: 1.45rem; margin-top: 1.8rem; }

p { margin-bottom: 1.3rem; text-align: justify; color: var(--text-main); }
ol, ul { margin-bottom: 1.6rem; padding-left: 1.6rem; }
li { margin-bottom: 0.6rem; }

blockquote {
    background: var(--glass-bg);
    border-left: 5px solid var(--deep-teal);
    padding: 1.6rem;
    margin: 1.8rem 0;
    font-style: italic;
    border-radius: 0 16px 16px 0;
    box-shadow: var(--shadow-deep);
}

img {
    max-width: 100%;
    height: auto;
    border-radius: 16px;
    object-fit: cover;
    transition: transform 0.4s ease;
    content-visibility: auto;
}
img[alt]:hover { transform: scale(1.015); }

/* ==========================================================================
   3. KHÓA KHÔNG GIAN ĐỈNH TRANG: PHÂN TẦNG MENU & DYNAMIC ISLAND
   ========================================================================== */
.liquid-glass {
    background: var(--glass-bg);
    backdrop-filter: blur(25px) saturate(200%);
    -webkit-backdrop-filter: blur(25px) saturate(200%);
    border: 1px solid var(--glass-border);
    box-shadow: var(--shadow-deep);
}

/* Hộp bảo vệ tối cao: Gom cụm Menu và Island cố định dòng chảy */
.super-header-capsule {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 9999;
    padding: 15px 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px; /* Khoảng cách không dịch chuyển giữa Menu và Island */
    pointer-events: none; /* Tránh cản trở cuộn chuột */
}

.nav-liquid {
    width: 100%;
    max-width: 1200px;
    padding: 12px 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-radius: 24px;
    pointer-events: auto; /* Kích hoạt lại tương tác click */
}

.logo img { height: 44px; width: auto; }
.menu-links { display: flex; gap: 10px; list-style: none; }
.menu-links a {
    color: var(--deep-teal);
    text-decoration: none;
    font-weight: 600;
    font-size: 14px;
    padding: 8px 18px;
    border-radius: 14px;
    transition: all 0.3s ease;
}
.menu-links a:hover, .menu-links a.active {
    background: #ffffff;
    box-shadow: 0 4px 12px rgba(0, 95, 115, 0.12);
}

/* Container của Dynamic Island nằm ngay dưới Menu */
.dynamic-island-container {
    width: auto;
    min-width: 290px;
    display: flex;
    justify-content: center;
    pointer-events: auto;
}

.dynamic-island {
    background: #000000;
    color: #ffffff;
    padding: 8px 24px;
    border-radius: 30px;
    font-size: 13px;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 10px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
    transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.island-dot {
    width: 8px; height: 8px; border-radius: 50%;
    background-color: var(--electric-cyan);
    box-shadow: 0 0 10px var(--electric-cyan);
}

/* ==========================================================================
   4. GIỌT NƯỚC CHẢY LIÊN HỆ TRÊN MOBILE (LIQUID DRIPPING DROPS)
   ========================================================================== */
.liquid-drop-widget {
    display: none;
    position: fixed;
    bottom: 30px;
    right: 20px;
    z-index: 9995;
}

.drop-button {
    width: 60px; height: 60px;
    background: linear-gradient(135deg, var(--deep-teal), #004554);
    border-radius: 50% 50% 50% 50% / 40% 40% 60% 60%;
    box-shadow: 0 12px 24px rgba(0, 95, 115, 0.35);
    display: flex; justify-content: center; align-items: center;
    cursor: pointer;
    animation: drip-pulsate 3s ease-in-out infinite;
    border: 1px solid rgba(255, 255, 255, 0.2);
}
.drop-button svg { width: 26px; height: 26px; fill: #ffffff; }

.drop-menu {
    position: absolute; bottom: 75px; right: 0;
    display: flex; flex-direction: column; gap: 15px;
    opacity: 0; transform: translateY(20px) scale(0.9);
    pointer-events: none;
    transition: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}
.drop-menu.show { opacity: 1; transform: translateY(0) scale(1); pointer-events: auto; }
.drop-item {
    width: 50px; height: 50px; border-radius: 50%;
    display: flex; justify-content: center; align-items: center;
    box-shadow: 0 8px 20px rgba(0,0,0,0.18);
    border: 1px solid rgba(255,255,255,0.4);
}
.drop-item.zalo { background: #0084FF; }
.drop-item.hotline { background: #28a745; }
.drop-item svg { width: 22px; height: 22px; fill: white; }

@keyframes drip-pulsate {
    0% { border-radius: 50% 50% 50% 50% / 40% 40% 60% 60%; transform: scale(1); }
    50% { border-radius: 44% 44% 56% 56% / 56% 56% 44% 44%; transform: scale(1.04); }
    100% { border-radius: 50% 50% 50% 50% / 40% 40% 60% 60%; transform: scale(1); }
}

/* ==========================================================================
   5. BỐ CỤC KHÔNG GIAN CHUẨN ĐỘC QUYỀN (CHỐNG CHỒNG LẤN 100%)
   ========================================================================== */
.main-wrapper {
    max-width: 1200px;
    margin: 175px auto 0 auto; /* Đệm cứng 175px hoàn hảo cho khoảng trống Desktop */
    padding: 0 20px;
    display: grid;
    grid-template-columns: 1fr;
    gap: 40px;
}

.section-padding { padding: 55px 35px; margin-bottom: 40px; }

/* Hero Parallax Section 1 */
.hero-parallax {
    position: relative;
    background-image: linear-gradient(rgba(240,247,249,0.88), rgba(240,247,249,0.88)), url('/img/lam-bang-dai-hoc-gia-re-uy-tin.webp');
    background-attachment: fixed; background-position: center; background-repeat: no-repeat; background-size: cover;
    border-radius: 28px;
}

/* Grids & Layout Parts */
.grid-2, .grid-3, .grid-4 { display: grid; grid-template-columns: 1fr; gap: 30px; }
@media (min-width: 768px) {
    .grid-2 { grid-template-columns: repeat(2, 1fr); }
    .grid-3 { grid-template-columns: repeat(3, 1fr); }
    .grid-4 { grid-template-columns: repeat(4, 1fr); }
}

.cta-btn {
    display: inline-block;
    background: linear-gradient(135deg, var(--deep-teal), #004554);
    color: #ffffff; padding: 14px 32px; border-radius: 30px;
    text-decoration: none; font-weight: 700; box-shadow: 0 8px 20px rgba(0,95,115,0.2);
    transition: all 0.3s ease;
}
.cta-btn:hover { transform: translateY(-2px); box-shadow: 0 12px 25px rgba(0,95,115,0.3); }

.table-responsive { overflow-x: auto; margin: 20px 0; }
table { width: 100%; border-collapse: collapse; background: var(--glass-bg); }
th, td { padding: 15px; text-align: left; border-bottom: 1px solid var(--glass-border); }
th { background-color: rgba(0, 95, 115, 0.06); color: var(--deep-teal); }

.accordion-item { border-bottom: 1px solid var(--glass-border); padding: 16px 0; }
.accordion-header { cursor: pointer; font-weight: 600; color: var(--deep-teal); display: flex; justify-content: space-between; }
.accordion-content { display: none; padding-top: 12px; color: var(--text-muted); }

footer { background: #0f1a1c; color: #a3b8ba; padding: 60px 0 30px 0; margin-top: 60px; }
footer h3 { color: #ffffff; margin-bottom: 15px; }
footer a { color: var(--electric-cyan); text-decoration: none; }
.footer-bottom { text-align: center; margin-top: 40px; padding-top: 20px; border-top: 1px solid rgba(255,255,255,0.05); }

/* ==========================================================================
   6. RESPONSIVE SỬA LỖI MOBILE TUYỆT ĐỐI (DÀNH CHO MÀN HÌNH NHỎ)
   ========================================================================== */
@media (max-width: 767px) {
    .super-header-capsule { padding: 10px 12px; gap: 8px; }
    .nav-liquid { padding: 10px 16px; border-radius: 16px; }
    .logo img { height: 34px; }
    
    .dynamic-island-container { min-width: 245px; }
    .dynamic-island { padding: 6px 16px; font-size: 12px; }
    .menu-links a { padding: 5px 10px; font-size: 12.5px; background: rgba(0, 95, 115, 0.05); border-radius: 10px; }

    /* GIẢI PHÁP SỬA LỖI CHỒNG LẤN: Tăng đệm an toàn vật lý của main flow lên hẳn 195px trên di động */
    .main-wrapper { 
        margin-top: 195px !important; 
        padding: 0 15px; 
    }
    .section-padding { padding: 30px 18px; margin-bottom: 25px; }
    .liquid-drop-widget { display: block; } /* Hiện giọt nước */
}