/* --- Color Variables --- */
:root {
    /* Mặc định là Light Mode (Giao diện gốc) */
    --primary-color: #c0392b; /* Màu đỏ của giao diện cũ */
    --bg-color: #ffffff;
    --secondary-bg-color: #f9f9f9;
    --text-color: #555;
    --heading-color: #2c3e50;
    --border-color: #e0e0e0;
    --card-bg: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.1);

    /* Biến màu riêng cho header để giữ vibe cyber */
    --header-primary-color: #00ff7f;
    --header-bg-color: rgba(13, 13, 13, 0.85);
    --header-text-color: #ccc;
    --header-border-color: #222;
}

body.dark-mode {
    /* Dark Mode "Cyber" Variables */
    --primary-color: #00ff7f;
    --bg-color: #050505;
    --secondary-bg-color: #0d0d0d;
    --text-color: #ccc;
    --heading-color: #fff;
    --border-color: #222;
    --card-bg: #1a1a1a;
    --shadow-color: rgba(0, 255, 127, 0.1);
}

/* --- Base & Reset --- */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    font-family: 'Be Vietnam Pro', sans-serif;
    line-height: 1.7;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* --- Layout & Typography --- */
.container { max-width: 1100px; margin: auto; overflow: hidden; padding: 0 2rem; }
section { padding: 5rem 0; border-bottom: 1px solid var(--border-color); }
h1, h2, h3, h4 { color: var(--heading-color); margin-bottom: 1.2rem; font-family: 'Roboto Mono', monospace; }
h2 { font-size: 2.5rem; text-align: center; }
.section-title-underline { width: 80px; height: 4px; background-color: var(--primary-color); margin: 0 auto 3rem auto; border-radius: 2px; }
a { text-decoration: none; color: var(--primary-color); }

/* --- Header (Luôn có giao diện tối) --- */
.main-header {
    background-color: var(--header-bg-color);
    backdrop-filter: blur(10px);
    padding: 0.5rem 0;
    position: sticky; top: 0; z-index: 1000;
    border-bottom: 1px solid var(--header-border-color);
}
.main-header .container { display: flex; justify-content: space-between; align-items: center; }
.logo { font-size: 1.5rem; font-weight: 700; color: var(--header-primary-color); font-family: 'Roboto Mono', monospace; }

/* --- Navigation (Luôn có giao diện tối) --- */
.main-nav ul { display: flex; list-style: none; }
.main-nav ul li a {
    color: var(--header-text-color);
    display: flex; flex-direction: column; align-items: center;
    padding: 0.5rem 0.8rem;
    font-size: 0.75rem;
    font-weight: 500;
    border-radius: 5px;
    transition: color 0.3s ease, background-color 0.3s ease;
}
.main-nav ul li a i { font-size: 1.2rem; margin-bottom: 0.25rem; }
.main-nav ul li a:hover { color: var(--header-primary-color); }
.main-nav ul li a.active {
    color: var(--header-primary-color);
    background-color: rgba(0, 255, 127, 0.1);
}

/* --- Header Controls (Luôn có giao diện tối) --- */
.header-controls { display: flex; align-items: center; gap: 0.5rem; }
.control-btn {
    background: none; border: none;
    color: var(--header-text-color);
    font-size: 1.2rem; cursor: pointer; padding: 0.5rem;
    border-radius: 50%; width: 40px; height: 40px;
    display: flex; align-items: center; justify-content: center;
    transition: background-color 0.3s, color 0.3s;
}
.control-btn:hover { color: var(--header-primary-color); background-color: #222; }
.search-input {
    width: 0; padding: 0.5rem 0; border: none;
    border-bottom: 2px solid var(--header-primary-color);
    background: transparent; color: var(--header-text-color);
    outline: none;
    transition: width 0.4s ease-in-out, padding 0.4s ease-in-out;
    opacity: 0;
}
.search-input.active { width: 200px; padding: 0.5rem; opacity: 1; }

/* --- Main Content Sections (Sử dụng biến màu chính) --- */
#hero {
    background: var(--bg-color);
    height: 100vh;
    display: flex; flex-direction: column; justify-content: center; align-items: center; text-align: center; border: none;
}
#hero h1 { font-size: 4rem; color: var(--heading-color); }
#hero .subtitle { font-size: 1.5rem; font-family: 'Roboto Mono', monospace; color: var(--text-color); }
.typing-effect { color: var(--primary-color); }
.typing-effect::after { content: '_'; display: inline-block; animation: blink 0.7s infinite; }
@keyframes blink { 50% { opacity: 0; } }

.btn, .btn-sm {
    display: inline-block;
    background: var(--primary-color);
    color: var(--card-bg) !important;
    padding: 0.8rem 1.5rem;
    border-radius: 5px;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    transition: background-color 0.3s ease;
}
.btn-sm { padding: 0.5rem 1rem; font-size: 0.9rem; }
.btn:hover { filter: brightness(1.1); }

#about { background-color: var(--secondary-bg-color); }
#about .container { display: flex; align-items: center; gap: 3rem; }
#about .about-image {
    /* Thay đổi kích thước ảnh ở đây */
    width: 200px;
    height: 200px;
    flex-shrink: 0; /* Ngăn ảnh bị co lại */
    border-radius: 50%;
    object-fit: cover;
    border: 5px solid var(--card-bg);
    box-shadow: 0 4px 10px var(--shadow-color);
}

section:nth-of-type(even) { background-color: var(--secondary-bg-color); }

.experience-item, .project-card, .skill-category, .education-item {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 4px 10px var(--shadow-color);
}
.experience-item h3, .project-card h3, .skill-category h4, .education-item h3 { color: var(--primary-color); }
.experience-item ul, .education-item ul { list-style-type: disc; padding-left: 1.2rem; }
.experience-item li, .education-item li { margin-bottom: 0.5rem; }

.projects-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 2rem; }
.project-card { display: flex; flex-direction: column; justify-content: space-between; }
.skills-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 2rem; }
.education-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 2rem; }

.hide { display: none !important; }
/* --- Contact Section --- */
#contact .container {
    display: flex;
    flex-direction: column;
    align-items: center; /* Căn giữa tất cả mọi thứ trong container theo chiều ngang */
    text-align: center;  /* Căn giữa các dòng chữ */
}

#contact p {
    max-width: 600px; /* Giới hạn chiều rộng của đoạn văn cho dễ đọc */
    margin-bottom: 2rem;
}
.main-footer { background-color: #2c3e50; color: #fff; text-align: center; padding: 2rem 0; }
.social-links a { color: #fff; }

@media (max-width: 1024px) { .nav-text { display: none; } }
@media (max-width: 768px) {
    .main-header .container { flex-direction: row; flex-wrap: wrap; justify-content: space-between; }
    .main-nav { order: 3; width: 100%; justify-content: center; margin-top: 0.5rem; }
    .header-controls { order: 2; }
    #hero h1 { font-size: 2.8rem; }
    #about .container { flex-direction: column; text-align: center; }
}