/* --- BIẾN TOÀN CỤC (Global Variables) --- */
:root {
    --bg-dark: #0f0f1a; /* Màu nền chính (tối) */
    --bg-light-glass: rgba(38, 43, 63, 0.5); /* Màu nền thủy tinh */
    --bg-card: #1b1f3a; /* Màu nền cho card (đậm hơn 1 chút) */
    --primary-color: #4A90E2; /* Màu nhấn (xanh dương hiện đại) */
    --secondary-color: #50E3C2; /* Màu nhấn phụ (xanh ngọc) */
    --text-primary: #FFFFFF; /* Màu chữ chính */
    --text-secondary: #a9a9b3; /* Màu chữ phụ */
    
    --font-heading: 'Montserrat', sans-serif;
    --font-body: 'Poppins', sans-serif;
    
    --container-width: 1140px;
    --border-radius: 12px;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

/* --- RESET & CÀI ĐẶT CHUNG --- */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    background-color: var(--bg-dark);
    color: var(--text-primary);
    font-family: var(--font-body);
    line-height: 1.7;
    overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    font-weight: 700;
    color: var(--text-primary);
}

h1 { font-size: 3.5rem; font-weight: 900; }
h2 { font-size: 2.5rem; }
h3 { font-size: 1.5rem; }

p {
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

a {
    text-decoration: none;
    color: var(--primary-color);
    transition: color 0.3s ease;
}

a:hover {
    color: var(--secondary-color);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

ul {
    list-style: none;
}

section {
    padding: 6rem 0;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 4px;
    background: var(--primary-color);
    margin: 0.5rem auto 0;
    border-radius: 2px;
}

.section-subtitle {
    text-align: center;
    max-width: 600px;
    margin: 0 auto 3rem;
    color: var(--text-secondary);
}

/* --- HIỆU ỨNG (Animations) --- */
.reveal-fade {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}
.reveal-fade.visible {
    opacity: 1;
    transform: translateY(0);
}

/* --- NÚT BẤM (Buttons) --- */
.btn {
    display: inline-block;
    padding: 0.8rem 2rem;
    border-radius: 50px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    box-shadow: 0 4px 15px rgba(74, 144, 226, 0.4);
}
.btn-primary:hover {
    background: var(--secondary-color);
    color: var(--bg-dark);
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(80, 227, 194, 0.4);
}

.btn-secondary {
    background: transparent;
    border-color: var(--secondary-color);
    color: var(--secondary-color);
}
.btn-secondary:hover {
    background: var(--secondary-color);
    color: var(--bg-dark);
    transform: translateY(-3px);
}

/* --- HEADER & NAVIGATION --- */
.header {
    width: 100%;
    position: fixed;
    top: 0;
    left: 0;
    z-index: 1000;
    background: rgba(15, 15, 26, 0.8);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}
.header nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 80px;
}
.logo {
    font-size: 1.5rem;
    font-weight: 900;
    font-family: var(--font-heading);
    color: var(--text-primary);
}
.nav-menu {
    display: flex;
    gap: 2rem;
}
.nav-menu a {
    color: var(--text-secondary);
    font-weight: 500;
    position: relative;
    padding: 0.5rem 0;
}
.nav-menu a:hover,
.nav-menu a.active {
    color: var(--text-primary);
}
.nav-menu a::after {
    content: '';
    display: block;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease;
    position: absolute;
    bottom: 0;
    left: 0;
}
.nav-menu a:hover::after { width: 100%; }
.hamburger { display: none; font-size: 1.5rem; cursor: pointer; }

/* --- HERO SECTION --- */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    text-align: center;
    background: linear-gradient(rgba(15, 15, 26, 0.9), rgba(15, 15, 26, 0.95));
    padding-top: 80px;
    position: relative;
    overflow: hidden;
}
#particles-js {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: 1;
}
.hero-content {
    position: relative;
    z-index: 2;
}
.hero-content h1 {
    font-size: 4rem;
    margin-bottom: 0.5rem;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.hero-content h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}
.typing-effect {
    color: var(--secondary-color);
    border-right: 2px solid var(--secondary-color);
    animation: blinkCursor 0.7s infinite;
}
@keyframes blinkCursor {
    from { border-right-color: var(--secondary-color); }
    to { border-right-color: transparent; }
}
.hero-content .subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 2.5rem;
}
.hero-buttons {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
}

/* --- ABOUT & STATS SECTION --- */
.about {
    padding-bottom: 3rem;
}
.about-content {
    text-align: center;
    max-width: 800px;
    margin: 0 auto 4rem;
}
.stats-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    text-align: center;
}
.stat-item {
    background: var(--bg-light-glass);
    padding: 2rem;
    border-radius: var(--border-radius);
    border: 1px solid rgba(255, 255, 255, 0.1);
}
.stat-item .stat-number {
    font-size: 3rem;
    font-weight: 900;
    color: var(--secondary-color);
}
.stat-item p {
    font-size: 1rem;
    color: var(--text-secondary);
    margin: 0;
}

/* --- TECH STACK SECTION --- */
.tech-stack {
    padding-top: 3rem;
}
.tech-grid {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 2rem;
}
.tech-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    padding: 1rem;
    background: var(--bg-card);
    border-radius: var(--border-radius);
    width: 120px;
    transition: all 0.3s ease;
}
.tech-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 5px 15px rgba(0,0,0,0.3);
}
.tech-item i {
    font-size: 3rem;
}
.tech-item span {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
}

/* --- SERVICES SECTION --- */
.services {
    background: var(--bg-dark); /* Slightly different dark */
}
.service-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2.5rem;
}
.service-card {
    background: var(--bg-card);
    padding: 2.5rem;
    border-radius: var(--border-radius);
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}
.service-card:hover {
    transform: translateY(-10px);
    border-color: var(--primary-color);
}
.service-card i {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}
.service-card h3 { margin-bottom: 1rem; }

/* --- PROJECTS SECTION --- */
.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2.5rem;
}
.project-card {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.project-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.4);
}
.project-card img {
    width: 100%;
    height: 220px;
    object-fit: cover;
    transition: transform 0.4s ease;
}
.project-card:hover img {
    transform: scale(1.05);
}
.project-info {
    padding: 1.5rem;
}
.project-info h3 {
    margin-bottom: 0.5rem;
}
.project-links {
    margin-top: 1.5rem;
    display: flex;
    gap: 1rem;
}
.btn-project, .btn-project-code {
    padding: 0.5rem 1.2rem;
    border-radius: 5px;
    font-weight: 500;
    font-size: 0.9rem;
}
.btn-project {
    background: var(--primary-color);
    color: white;
}
.btn-project-code {
    background: transparent;
    border: 1px solid var(--text-secondary);
    color: var(--text-secondary);
}
.btn-project-code:hover {
    background: var(--text-secondary);
    color: var(--bg-dark);
}

/* --- PROCESS SECTION --- */
.process-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    text-align: center;
}
.process-step {
    padding: 2rem;
}
.process-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    display: inline-block;
    background: var(--bg-light-glass);
    width: 80px;
    height: 80px;
    line-height: 80px;
    border-radius: 50%;
}
.process-step h3 {
    margin-bottom: 1rem;
}

/* --- TESTIMONIALS SECTION --- */
.testimonials {
    background: var(--bg-card);
}
.testimonial-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2.5rem;
}
.testimonial-card {
    background: var(--bg-light-glass);
    padding: 2.5rem;
    border-radius: var(--border-radius);
    border-left: 5px solid var(--primary-color);
}
.testimonial-card p {
    font-style: italic;
    font-size: 1.1rem;
    color: var(--text-primary);
}
.testimonial-card cite {
    display: block;
    margin-top: 1rem;
    font-weight: 600;
    color: var(--secondary-color);
}

/* --- FAQ SECTION --- */
.faq-accordion {
    max-width: 800px;
    margin: 0 auto;
}
.faq-accordion details {
    background: var(--bg-card);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    margin-bottom: 1rem;
    overflow: hidden;
}
.faq-accordion summary {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    cursor: pointer;
    font-size: 1.1rem;
    font-weight: 600;
    list-style: none; /* Xóa mũi tên mặc định */
}
.faq-accordion summary::-webkit-details-marker { display: none; }
.faq-accordion summary i {
    color: var(--primary-color);
    transition: transform 0.3s ease;
}
.faq-accordion details[open] summary i {
    transform: rotate(45deg);
}
.faq-accordion details p {
    padding: 0 1.5rem 1.5rem;
    margin: 0;
    color: var(--text-secondary);
}

/* --- CTA SECTION --- */
.cta-section {
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
    text-align: center;
    padding: 4rem 2rem;
}
.cta-section h2 {
    font-size: 2.2rem;
    color: var(--bg-dark);
}
.cta-section p {
    font-size: 1.1rem;
    color: var(--bg-dark);
    margin-bottom: 2rem;
}
.cta-section .btn-primary {
    background: var(--text-primary);
    color: var(--bg-dark);
    box-shadow: none;
}
.cta-section .btn-primary:hover {
    background: var(--bg-dark);
    color: var(--text-primary);
}


/* --- CONTACT SECTION --- */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: 3rem;
    background: var(--bg-card);
    padding: 3rem;
    border-radius: var(--border-radius);
}
.contact-info ul li {
    display: flex;
    align-items: center;
    gap: 1rem;
    font-size: 1.1rem;
    margin-bottom: 1.5rem;
}
.contact-info i {
    font-size: 1.5rem;
    width: 30px;
    text-align: center;
    color: var(--primary-color);
}
/* Contact Form */
.form-group { margin-bottom: 1.5rem; }
.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-secondary);
}
.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.8rem 1rem;
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    color: var(--text-primary);
    font-family: var(--font-body);
}
.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(74, 144, 226, 0.3);
}
#form-status { margin-top: 1rem; font-size: 0.9rem; }

/* --- FOOTER --- */
.footer {
    text-align: center;
    padding: 2rem;
    background: #0a0a10;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* --- RESPONSIVE DESIGN --- */
@media (max-width: 992px) {
    .container { padding: 0 1.5rem; }
    h1 { font-size: 3rem; }
    .hero-content h1 { font-size: 3rem; }
    .hero-content h2 { font-size: 2rem; }
    
    .testimonial-grid { grid-template-columns: 1fr; }
    .contact-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
    /* Mobile Menu */
    .nav-menu {
        position: fixed;
        top: 80px; 
        right: -100%; 
        width: 100%;
        height: calc(100vh - 80px);
        background: var(--bg-dark);
        flex-direction: column;
        justify-content: center;
        align-items: center;
        gap: 2rem;
        transition: right 0.4s ease-in-out;
    }
    .nav-menu.active { right: 0; }
    .nav-menu a { font-size: 1.5rem; }
    .hamburger { display: block; }
    
    section { padding: 4rem 0; }

    .hero-content { text-align: left; }
    .hero-buttons { flex-direction: column; align-items: flex-start; }
    
    .stats-grid { grid-template-columns: 1fr; }
    .service-grid { grid-template-columns: 1fr; }
    .project-grid { grid-template-columns: 1fr; }
    .process-grid { grid-template-columns: 1fr; }
    .contact-grid { padding: 2rem; }
    .section-title { font-size: 2rem; }
}
/* Thêm vào cuối file style.css */
.svg-icon {
    width: 1.25em; /* Kích thước tương đương icon Font Awesome */
    height: 1.25em;
    fill: var(--primary-color); /* Tô màu xanh giống các icon khác */
    margin-right: -0.25em; /* Căn chỉnh cho thẳng hàng */
}