@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600&family=Lora:ital,wght@0,400;0,700;1,400&display=swap');

:root {
    --bg-white: #ffffff;
    --bg-light: #f8f9fa;
    --text-dark: #1a1a1a;
    --text-muted: #5a5a5a;
    --primary-blue: #2c3e50;
    --accent-blue: #3498db;
    --border-color: #e9ecef;
}

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

body {
    background-color: var(--bg-white);
    color: var(--text-dark);
    font-family: 'Inter', sans-serif;
    line-height: 1.8;
    overflow-x: hidden;
}

h1, h2, h3, h4 {
    font-family: 'Lora', serif;
    font-weight: 700;
    color: var(--primary-blue);
    line-height: 1.2;
}

/* --- NAVIGATION --- */
nav {
    padding: 25px 8%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(5px);
    z-index: 1000;
}

.logo {
    font-size: 1.4rem;
    font-weight: 700;
    letter-spacing: -0.5px;
    color: var(--primary-blue);
    text-transform: uppercase;
}

.logo span { color: var(--accent-blue); }

.nav-links a {
    text-decoration: none;
    color: var(--text-dark);
    font-size: 0.85rem;
    font-weight: 600;
    margin-left: 35px;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: 0.3s;
}

.nav-links a:hover { color: var(--accent-blue); }

/* --- SECTIONS --- */
.container {
    max-width: 1200px;
    margin: auto;
    padding: 100px 5%;
}

.hero {
    padding: 120px 5%;
    text-align: center;
    background-color: var(--bg-light);
}

.hero h1 { font-size: 3.5rem; margin-bottom: 20px; }
.hero p { font-size: 1.2rem; color: var(--text-muted); max-width: 700px; margin: auto; }

/* --- CARDS --- */
.grid-3 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 40px;
    margin-top: 60px;
}

.academic-card {
    padding: 40px;
    background: var(--bg-white);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    transition: 0.3s;
}

.academic-card:hover {
    box-shadow: 0 15px 40px rgba(0,0,0,0.05);
    border-color: var(--accent-blue);
}

.person-img {
    width: 120px;
    height: 120px;
    border-radius: 50%;
    object-fit: cover;
    margin-bottom: 20px;
    border: 3px solid var(--bg-light);
    background-color: var(--bg-light);
}

/* --- BUTTONS --- */
.btn {
    padding: 14px 30px;
    font-weight: 600;
    text-decoration: none;
    border-radius: 2px;
    display: inline-block;
    transition: 0.3s;
    font-size: 0.9rem;
}

.btn-dark { background: var(--primary-blue); color: #fff; }
.btn-dark:hover { background: var(--accent-blue); }

/* --- FOOTER --- */
footer {
    padding: 80px 8%;
    background: var(--bg-light);
    border-top: 1px solid var(--border-color);
    text-align: center;
}

/* Secret Member Security Masks */
.secret-container {
    position: relative;
}
.secret-mask {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: #1a1a1a;
    color: #fff;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    z-index: 100;
    transition: all 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    border-radius: 4px;
    border: 1px solid #333;
}
.secret-mask:hover {
    border-color: var(--accent-blue);
    box-shadow: 0 0 15px rgba(52, 152, 219, 0.4);
}
.secret-mask span {
    font-family: 'Courier New', Courier, monospace;
    font-size: 0.9rem;
    font-weight: bold;
    letter-spacing: 3px;
    margin-bottom: 10px;
}
.secret-mask .lock-icon {
    font-size: 1.5rem;
    margin-bottom: 15px;
}

#mask-tuan {
    background-image: linear-gradient(rgba(0,0,0,0.2), rgba(0,0,0,0.4)), url('images/bg_area1.png');
    background-size: cover;
    background-position: center;
}
#mask-duy {
    background-image: linear-gradient(rgba(0,0,0,0.2), rgba(0,0,0,0.4)), url('images/bg_area2.png');
    background-size: cover;
    background-position: center;
}
#mask-luong {
    background-image: linear-gradient(rgba(0,0,0,0.2), rgba(0,0,0,0.4)), url('images/bg_tree.png');
    background-size: cover;
    background-position: center;
}
#mask-hieu {
    background-image: linear-gradient(rgba(0,0,0,0.2), rgba(0,0,0,0.4)), url('images/bg_brix.png');
    background-size: cover;
    background-position: center;
}