/* ============================================================
   Design System — Zalo Blue × White × Black
   ============================================================ */
:root {
    --zalo-blue: #0068FF;
    --zalo-blue-dark: #0050CC;
    --zalo-blue-light: rgba(0, 104, 255, 0.08);
    --zalo-blue-glow: rgba(0, 104, 255, 0.15);
    --black: #0A0A0F;
    --black-soft: #14141A;
    --gray-900: #1C1C24;
    --gray-800: #26262F;
    --gray-700: #363640;
    --gray-400: #8E8E99;
    --gray-300: #ACACB5;
    --white: #FFFFFF;
    --white-soft: #F4F5F7;
    --glass: rgba(10, 10, 15, 0.75);
    --glass-border: rgba(255, 255, 255, 0.06);
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.25);
    --shadow-blue: 0 8px 30px rgba(0, 104, 255, 0.2);
    --radius: 16px;
    --radius-lg: 28px;
    --transition: all 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background-color: var(--black);
    color: var(--white);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* ===== Preloader ===== */
.preloader {
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: var(--black);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
}

.loader {
    width: 44px; height: 44px;
    border: 3px solid var(--gray-800);
    border-top: 3px solid var(--zalo-blue);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin { to { transform: rotate(360deg); } }

/* ===== Buttons ===== */
.btn-primary {
    display: inline-block;
    padding: 0.9rem 2rem;
    background: var(--zalo-blue);
    color: var(--white);
    text-decoration: none;
    border-radius: 50px;
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
    border: 2px solid var(--zalo-blue);
    box-shadow: var(--shadow-blue);
}

.btn-primary:hover {
    background: var(--zalo-blue-dark);
    border-color: var(--zalo-blue-dark);
    transform: translateY(-3px);
    box-shadow: 0 12px 35px rgba(0, 104, 255, 0.3);
}

.btn-secondary {
    display: inline-block;
    padding: 0.9rem 2rem;
    background: transparent;
    color: var(--white);
    text-decoration: none;
    border-radius: 50px;
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
    border: 2px solid var(--gray-700);
}

.btn-secondary:hover {
    border-color: var(--zalo-blue);
    color: var(--zalo-blue);
    transform: translateY(-3px);
}

/* ===== Navbar ===== */
.navbar {
    position: fixed;
    top: 0; left: 0; width: 100%;
    padding: 1.25rem 0;
    z-index: 1000;
    transition: var(--transition);
}

.navbar.scrolled {
    background: var(--glass);
    -webkit-backdrop-filter: blur(20px);
    backdrop-filter: blur(20px);
    padding: 0.85rem 0;
    border-bottom: 1px solid var(--glass-border);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--white);
    text-decoration: none;
    letter-spacing: -1px;
}
.logo span { color: var(--zalo-blue); }

.nav-links {
    display: flex;
    list-style: none;
    gap: 2.5rem;
    align-items: center;
}

.nav-links a {
    text-decoration: none;
    color: var(--gray-300);
    font-weight: 500;
    font-size: 0.95rem;
    transition: var(--transition);
}
.nav-links a:hover { color: var(--white); }
.nav-links a.btn-primary { color: var(--white); }
.nav-links a.btn-primary:hover { color: var(--white); }

.donate-link {
    color: var(--zalo-blue) !important;
    font-weight: 600 !important;
}
.donate-link i {
    animation: donateHeartbeat 2s ease-in-out infinite;
}
.donate-link:hover {
    color: #3388FF !important;
}

@keyframes donateHeartbeat {
    0%, 100% { transform: scale(1); }
    10% { transform: scale(1.2); }
    20% { transform: scale(1); }
    30% { transform: scale(1.15); }
    40%, 100% { transform: scale(1); }
}

/* ===== Scroll Indicator ===== */
.scroll-indicator {
    position: absolute;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
}

.mouse {
    width: 24px; height: 38px;
    border: 2px solid var(--gray-700);
    border-radius: 12px;
    position: relative;
}
.mouse::after {
    content: '';
    position: absolute;
    top: 6px; left: 50%;
    transform: translateX(-50%);
    width: 3px; height: 8px;
    background: var(--zalo-blue);
    border-radius: 3px;
    animation: scrollMouse 1.5s ease-in-out infinite;
}
@keyframes scrollMouse {
    0% { opacity: 1; transform: translateX(-50%) translateY(0); }
    100% { opacity: 0; transform: translateX(-50%) translateY(14px); }
}

/* ===== Hero Section ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: 80px;
    position: relative;
    background:
        radial-gradient(ellipse 60% 50% at 10% 90%, rgba(0,104,255,0.08) 0%, transparent 60%),
        radial-gradient(ellipse 40% 40% at 80% 20%, rgba(0,104,255,0.05) 0%, transparent 60%),
        var(--black);
}

.hero .container {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 4rem;
    align-items: center;
}

.badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1.2rem;
    background: var(--zalo-blue-light);
    color: var(--zalo-blue);
    border: 1px solid rgba(0,104,255,0.15);
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
}

.hero h1 {
    font-size: 4.2rem;
    line-height: 1.08;
    margin-bottom: 1.5rem;
    color: var(--white);
    letter-spacing: -1.5px;
}
.hero h1 span {
    display: block;
    background: linear-gradient(135deg, var(--zalo-blue), #3399FF);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.tagline {
    font-size: 1.4rem;
    font-weight: 500;
    color: var(--gray-400);
    margin-bottom: 1.5rem;
}

.hero .description {
    font-size: 1.05rem;
    color: var(--gray-400);
    max-width: 500px;
    margin-bottom: 2.5rem;
    line-height: 1.7;
}

.hero-btns {
    display: flex;
    gap: 1.2rem;
}

/* Hero Image */
.hero-image { position: relative; }

.image-wrapper {
    position: relative;
    width: 100%;
    aspect-ratio: 1/1.2;
    background: linear-gradient(135deg, var(--gray-900), var(--gray-800));
    border-radius: var(--radius-lg);
    overflow: hidden;
    border: 1px solid var(--glass-border);
}
.image-wrapper img {
    width: 100%; height: 100%;
    object-fit: cover;
    object-position: center 15%;
}

.experience-badge {
    position: absolute;
    bottom: 20px; left: 20px;
    background: var(--zalo-blue);
    color: var(--white);
    padding: 1.2rem 1.5rem;
    border-radius: 18px;
    text-align: center;
    box-shadow: var(--shadow-blue);
    z-index: 2;
}
.experience-badge span {
    font-size: 2rem; font-weight: 700;
    display: block; line-height: 1;
}
.experience-badge p {
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-top: 4px;
    opacity: 0.85;
}

/* ===== Marquee ===== */
.marquee {
    background: linear-gradient(90deg, var(--zalo-blue), var(--zalo-blue-dark), var(--zalo-blue));
    padding: 1.5rem 0;
    overflow: hidden;
    white-space: nowrap;
}

.marquee-content {
    display: inline-block;
    animation: marquee 30s linear infinite;
}

.marquee-content span {
    color: var(--white);
    font-size: 1.3rem;
    font-weight: 600;
    margin-right: 3.5rem;
    text-transform: uppercase;
    opacity: 0.9;
    letter-spacing: 0.5px;
}

@keyframes marquee {
    0% { transform: translateX(0); }
    100% { transform: translateX(-50%); }
}

/* ===== Sections ===== */
section { padding: 100px 0; }

.section-header {
    margin-bottom: 60px;
    text-align: center;
}
.section-header h2 {
    font-size: 2.4rem;
    color: var(--white);
    margin-bottom: 0.75rem;
    letter-spacing: -0.5px;
}
.section-header p {
    color: var(--gray-400);
    font-size: 1.05rem;
}

/* ===== About / Timeline ===== */
.about {
    background:
        radial-gradient(ellipse 50% 40% at 80% 50%, rgba(0,104,255,0.04) 0%, transparent 60%),
        var(--black-soft);
}

.timeline {
    max-width: 800px;
    margin: 0 auto;
    position: relative;
}
.timeline::before {
    content: '';
    position: absolute;
    left: 0; top: 0;
    height: 100%; width: 2px;
    background: linear-gradient(to bottom, var(--zalo-blue), var(--gray-800));
}

.timeline-item {
    position: relative;
    padding-left: 50px;
    margin-bottom: 50px;
}
.timeline-item::before {
    content: '';
    position: absolute;
    left: -5px; top: 0;
    width: 12px; height: 12px;
    background: var(--zalo-blue);
    border-radius: 50%;
    box-shadow: 0 0 12px rgba(0,104,255,0.4);
}

.year {
    font-weight: 700;
    color: var(--zalo-blue);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.timeline-item h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    color: var(--white);
}

.timeline-item p {
    color: var(--gray-400);
}

/* ===== Services ===== */
.services {
    background: var(--black);
}

.services-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 1.5rem;
}

.service-card {
    background: var(--gray-900);
    padding: 2.5rem 2rem;
    border-radius: var(--radius-lg);
    transition: var(--transition);
    border: 1px solid var(--glass-border);
    position: relative;
    overflow: hidden;
}
.service-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 3px;
    background: linear-gradient(90deg, var(--zalo-blue), transparent);
    opacity: 0;
    transition: var(--transition);
}
.service-card:hover {
    transform: translateY(-8px);
    border-color: rgba(0,104,255,0.15);
    box-shadow: 0 20px 40px rgba(0,0,0,0.3);
}
.service-card:hover::before { opacity: 1; }

.service-card .icon {
    width: 56px; height: 56px;
    background: var(--zalo-blue-light);
    border-radius: 14px;
    display: flex;
    justify-content: center;
    align-items: center;
    margin-bottom: 1.5rem;
    font-size: 1.4rem;
    color: var(--zalo-blue);
    transition: var(--transition);
}
.service-card:hover .icon {
    background: var(--zalo-blue);
    color: var(--white);
}

.service-card h3 {
    margin-bottom: 0.75rem;
    font-size: 1.25rem;
    color: var(--white);
}
.service-card p {
    color: var(--gray-400);
    font-size: 0.95rem;
    line-height: 1.6;
}

/* ===== Skills ===== */
.skills {
    background:
        radial-gradient(ellipse 50% 50% at 20% 50%, rgba(0,104,255,0.04) 0%, transparent 60%),
        var(--black-soft);
}

.skills-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.skills-info h2 {
    font-size: 2.2rem;
    margin-bottom: 1rem;
    letter-spacing: -0.5px;
}
.skills-info p {
    color: var(--gray-400);
    font-size: 1.05rem;
    line-height: 1.7;
}

.skill-item { margin-bottom: 1.8rem; }

.skill-info {
    display: flex;
    justify-content: space-between;
    margin-bottom: 0.6rem;
    font-weight: 600;
    font-size: 0.95rem;
}
.skill-info span:last-child { color: var(--zalo-blue); }

.progress-bar {
    height: 6px;
    background: var(--gray-800);
    border-radius: 10px;
    overflow: hidden;
}
.progress {
    height: 100%;
    background: linear-gradient(90deg, var(--zalo-blue), #3399FF);
    border-radius: 10px;
    transition: width 1.5s ease;
}

/* ===== Projects ===== */
.projects {
    background: var(--black);
}

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
    gap: 1.5rem;
}

.project-card {
    border-radius: var(--radius-lg);
    overflow: hidden;
    background: var(--gray-900);
    transition: var(--transition);
    border: 1px solid var(--glass-border);
}
.project-card:hover {
    transform: translateY(-6px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.3);
    border-color: rgba(0,104,255,0.15);
}

.project-img {
    height: 220px;
    background: linear-gradient(135deg, var(--zalo-blue), var(--black));
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow: hidden;
}
.project-img::after {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: linear-gradient(to bottom, transparent 50%, var(--gray-900));
}

.placeholder-img {
    font-size: 1.4rem;
    font-weight: 700;
    opacity: 0.25;
    color: var(--white);
    z-index: 1;
}

.project-info { padding: 1.5rem 2rem 2rem; }
.project-info h3 {
    margin-bottom: 0.75rem;
    font-size: 1.2rem;
    color: var(--white);
}
.project-info p {
    color: var(--gray-400);
    font-size: 0.95rem;
}

.tags {
    margin-top: 1.2rem;
    display: flex;
    gap: 0.6rem;
}
.tags span {
    padding: 0.35rem 0.9rem;
    background: var(--zalo-blue-light);
    color: var(--zalo-blue);
    border-radius: 50px;
    font-size: 0.78rem;
    font-weight: 600;
}

/* ===== Contact ===== */
.contact {
    background:
        radial-gradient(ellipse 60% 50% at 50% 80%, rgba(0,104,255,0.06) 0%, transparent 60%),
        var(--black-soft);
}

.contact-box {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    background: var(--gray-900);
    padding: 3.5rem;
    border-radius: var(--radius-lg);
    border: 1px solid var(--glass-border);
    box-shadow: var(--shadow);
}

.contact-info h2 {
    font-size: 2.2rem;
    margin-bottom: 1.2rem;
    letter-spacing: -0.5px;
    line-height: 1.2;
}
.contact-info > p {
    color: var(--gray-400);
    line-height: 1.7;
}

.info-list { margin: 2.5rem 0; }

.info-item {
    display: flex;
    gap: 1.2rem;
    margin-bottom: 1.8rem;
}
.info-item i {
    font-size: 1.1rem;
    color: var(--zalo-blue);
    margin-top: 4px;
    width: 20px;
    text-align: center;
}
.info-item span {
    display: block;
    font-size: 0.8rem;
    color: var(--gray-400);
    margin-bottom: 2px;
}
.info-item p {
    font-weight: 500;
    font-size: 0.95rem;
}

.social-links {
    display: flex;
    gap: 0.8rem;
}
.social-links a {
    width: 42px; height: 42px;
    border: 1px solid var(--gray-700);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    color: var(--gray-400);
    text-decoration: none;
    transition: var(--transition);
    font-size: 0.95rem;
}
.social-links a:hover {
    background: var(--zalo-blue);
    border-color: var(--zalo-blue);
    color: var(--white);
}

.contact-form .form-group { margin-bottom: 1.2rem; }

.contact-form input, .contact-form textarea {
    width: 100%;
    padding: 1rem 1.2rem;
    background: var(--gray-800);
    border: 1px solid var(--gray-700);
    border-radius: 12px;
    color: var(--white);
    font-family: inherit;
    font-size: 0.95rem;
    outline: none;
    transition: var(--transition);
}
.contact-form input::placeholder, .contact-form textarea::placeholder {
    color: var(--gray-400);
}
.contact-form input:focus, .contact-form textarea:focus {
    border-color: var(--zalo-blue);
    background: rgba(0,104,255,0.04);
}

.contact-form .btn-primary {
    width: 100%;
    border: none;
    cursor: pointer;
    font-family: inherit;
}

/* ===== Footer ===== */
footer {
    padding: 2.5rem 0;
    text-align: center;
    border-top: 1px solid var(--glass-border);
}
footer p {
    color: var(--gray-400);
    font-size: 0.85rem;
}

/* ===== Responsive ===== */
@media (max-width: 992px) {
    .hero .container, .skills-wrapper, .contact-box {
        grid-template-columns: 1fr;
    }
    .hero {
        min-height: auto;
        padding: 120px 0 60px;
    }
    .hero h1 { font-size: 3.2rem; }
    .hero-image {
        order: -1;
        max-width: 500px;
        margin: 0 auto;
    }
    .nav-links { display: none; }
}

@media (max-width: 600px) {
    .hero h1 { font-size: 2.6rem; }
    .contact-box { padding: 2rem; }
    .section-header h2 { font-size: 2rem; }
    .projects-grid { grid-template-columns: 1fr; }
}