/* 
=========================================
CSS Variables & Design Tokens 
=========================================
*/
:root {
    /* Colors */
    --duo-green: #58cc02;
    --duo-green-dark: #46a302;
    --duo-green-light: #79e028;
    
    --duo-super-blue: #1cb0f6;
    --duo-super-blue-dark: #1899d6;
    
    --duo-max-purple: #c250e7;
    --duo-max-purple-dark: #a13ebd;
    
    --duo-gray-100: #e5e5e5;
    --duo-gray-200: #afafaf;
    --duo-gray-400: #777777;
    --duo-gray-800: #3c3c3c;
    
    --text-main: #4b4b4b;
    --bg-main: #ffffff;
    --bg-night: #0b0c10;
    
    --white: #ffffff;
    --black: #000000;
    
    /* Typography */
    --font-main: 'Nunito', sans-serif;
    
    /* Spacing */
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 64px;
    
    /* Effects */
    --shadow-sm: 0 4px 0 rgba(0,0,0,0.1);
    --shadow-md: 0 8px 24px rgba(0,0,0,0.1);
    --shadow-lg: 0 20px 40px rgba(0,0,0,0.15);
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --radius-full: 9999px;
}

/* 
=========================================
Base Styles
=========================================
*/
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-main);
    color: var(--text-main);
    background-color: var(--bg-main);
    line-height: 1.6;
    overflow-x: hidden;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-md);
}

/* 
=========================================
Typography
=========================================
*/
h1, h2, h3, h4, h5, h6 {
    font-weight: 800;
    color: var(--duo-gray-800);
    margin-bottom: var(--space-md);
    line-height: 1.2;
}

a {
    text-decoration: none;
    color: inherit;
    transition: all 0.2s ease;
}

/* 
=========================================
Buttons
=========================================
*/
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 12px 24px;
    border-radius: var(--radius-md);
    font-weight: 800;
    font-size: 16px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    cursor: pointer;
    transition: all 0.1s ease;
    border: 2px solid transparent;
    border-bottom-width: 4px;
}

.btn:active {
    transform: translateY(2px);
    border-bottom-width: 2px;
    margin-top: 2px;
}

.btn-primary {
    background-color: var(--duo-green);
    color: var(--white);
    border-color: var(--duo-green-dark);
}

.btn-primary:hover {
    background-color: var(--duo-green-light);
}

.btn-super {
    background-color: var(--duo-super-blue);
    color: var(--white);
    border-color: var(--duo-super-blue-dark);
}

.btn-max {
    background-color: var(--duo-max-purple);
    color: var(--white);
    border-color: var(--duo-max-purple-dark);
}

.btn-zalo-outline {
    background-color: transparent;
    color: #0068ff;
    border-color: var(--duo-gray-100);
}

.btn-zalo-outline:hover {
    background-color: rgba(0, 104, 255, 0.05);
    border-color: #0068ff;
}

/* 
=========================================
Navbar
=========================================
*/
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    z-index: 1000;
    border-bottom: 2px solid var(--duo-gray-100);
    padding: 10px 0;
}

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

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 24px;
    font-weight: 900;
    color: var(--duo-green);
}

.premium-text {
    background: linear-gradient(90deg, var(--duo-super-blue), var(--duo-max-purple));
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.desktop-nav a {
    margin: 0 15px;
    font-weight: 700;
    color: var(--duo-gray-400);
    text-transform: uppercase;
    font-size: 14px;
    letter-spacing: 1px;
}

.desktop-nav a:hover {
    color: var(--duo-super-blue);
}

.nav-actions {
    display: flex;
    gap: 10px;
}

/* 
=========================================
Floating Widgets
=========================================
*/
.floating-widgets {
    position: fixed;
    bottom: 30px;
    right: 30px;
    display: flex;
    flex-direction: column;
    gap: 15px;
    z-index: 999;
}

.widget-btn {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 10px 20px rgba(0,0,0,0.2);
    cursor: pointer;
    font-size: 24px;
    color: white;
    text-decoration: none;
    transition: transform 0.2s ease;
}

.widget-btn:hover {
    transform: scale(1.1);
}

.widget-zalo {
    background-color: white;
}

.widget-zalo img {
    width: 35px;
    height: 35px;
    object-fit: contain;
}

.widget-phone {
    background-color: #f12711;
    background: linear-gradient(to right, #f5af19, #f12711);
}

/* Animations */
@keyframes pulsing {
    0% {
        box-shadow: 0 0 0 0 rgba(0, 104, 255, 0.7);
    }
    70% {
        box-shadow: 0 0 0 15px rgba(0, 104, 255, 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(0, 104, 255, 0);
    }
}

@keyframes pulsing-red {
    0% {
        box-shadow: 0 0 0 0 rgba(241, 39, 17, 0.7);
    }
    70% {
        box-shadow: 0 0 0 15px rgba(241, 39, 17, 0);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(241, 39, 17, 0);
    }
}

.pulsing {
    animation: pulsing 2s infinite;
}

.pulsing-delay {
    animation: pulsing-red 2s infinite;
    animation-delay: 1s;
}

/* 
=========================================
Hero Section & Starry Night
=========================================
*/
.hero-section {
    position: relative;
    padding: 160px 0 100px;
    background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
    overflow: hidden;
    color: white;
}

/* Star Background Effects */
@keyframes move-twink-back {
    from {background-position: 0 0;}
    to {background-position: -10000px 5000px;}
}

.stars, .twinkling {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    height: 100%;
    display: block;
}

.stars {
    background: #000 url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200"><circle cx="20" cy="20" r="1" fill="white" fill-opacity="0.8"/><circle cx="150" cy="50" r="1.5" fill="white" fill-opacity="0.9"/><circle cx="80" cy="120" r="1" fill="white" fill-opacity="0.6"/><circle cx="180" cy="180" r="2" fill="white" fill-opacity="0.7"/><circle cx="50" cy="160" r="1.2" fill="white" fill-opacity="0.8"/></svg>') repeat top center;
    z-index: 0;
}

.twinkling {
    background: transparent url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="400" height="400"><circle cx="50" cy="350" r="1.5" fill="white" fill-opacity="0.5"/><circle cx="350" cy="150" r="2" fill="white" fill-opacity="0.6"/><circle cx="200" cy="250" r="1" fill="white" fill-opacity="0.8"/><circle cx="300" cy="300" r="1.5" fill="white" fill-opacity="0.7"/></svg>') repeat top center;
    z-index: 1;
    animation: move-twink-back 200s linear infinite;
}

/* Floating Language Flags */
.flags-container {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: 1;
    pointer-events: none;
}

.floating-flag {
    position: absolute;
    user-select: none;
    opacity: 0.6;
    animation: drift linear infinite;
    filter: drop-shadow(0 2px 5px rgba(0,0,0,0.3));
    font-size: 24px;
}

@keyframes drift {
    0% {
        transform: translateY(110vh) rotate(0deg);
        opacity: 0;
    }
    10% {
        opacity: 0.8;
    }
    90% {
        opacity: 0.8;
    }
    100% {
        transform: translateY(-20vh) rotate(360deg);
        opacity: 0;
    }
}

.hero-content {
    position: relative;
    z-index: 2;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 40px;
}

.hero-text {
    flex: 1;
    max-width: 600px;
}

.hero-text h1 {
    color: white;
    font-size: 48px;
    margin-bottom: 20px;
    text-shadow: 0 4px 10px rgba(0,0,0,0.3);
}

.hero-text p {
    font-size: 18px;
    margin-bottom: 30px;
    color: #e0e0e0;
    font-weight: 600;
}

.badge {
    display: inline-block;
    padding: 8px 16px;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 20px;
    font-size: 14px;
    font-weight: 700;
    margin-bottom: 20px;
    backdrop-filter: blur(5px);
    color: #ffd700;
}

.hero-buttons {
    display: flex;
    gap: 15px;
}

.btn-outline {
    background-color: transparent !important;
    border: 2px solid white !important;
}

.btn-outline:hover {
    background-color: rgba(255, 255, 255, 0.1) !important;
}

.hero-image {
    flex: 1;
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

.glow-effect {
    position: absolute;
    width: 300px;
    height: 300px;
    background: radial-gradient(circle, rgba(88, 204, 2, 0.4) 0%, rgba(28, 176, 246, 0.1) 50%, transparent 70%);
    border-radius: 50%;
    z-index: -1;
    animation: pulse-glow 4s ease-in-out infinite alternate;
}

@keyframes pulse-glow {
    0% { transform: scale(0.8); opacity: 0.5; }
    100% { transform: scale(1.2); opacity: 1; }
}

/* 3D Owl Animation */
.owl-3d {
    width: 100%;
    max-width: 450px;
    animation: float 4s ease-in-out infinite;
    filter: drop-shadow(0 20px 30px rgba(0,0,0,0.3));
}

@keyframes float {
    0% { transform: translateY(0px) rotate(0deg); }
    50% { transform: translateY(-20px) rotate(2deg); }
    100% { transform: translateY(0px) rotate(0deg); }
}

.wave-bottom {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    overflow: hidden;
    line-height: 0;
    transform: rotate(180deg);
}

.wave-bottom svg {
    position: relative;
    display: block;
    width: calc(100% + 1.3px);
    height: 80px;
}

.wave-bottom .shape-fill {
    fill: var(--bg-main);
}

/* 
=========================================
General Sections
=========================================
*/
.section {
    padding: 80px 0;
}

.bg-light {
    background-color: #f9f9f9;
}

.section-title {
    font-size: 36px;
    margin-bottom: 20px;
    color: var(--duo-gray-800);
}

.section-subtitle {
    font-size: 18px;
    color: var(--text-main);
    margin-bottom: 50px;
}

.text-center { text-align: center; }
.mt-4 { margin-top: 40px; }
.btn-lg { padding: 15px 30px; font-size: 18px; }
.btn-block { width: 100%; display: flex; }

.text-green { color: var(--duo-green); }
.text-purple { color: var(--duo-max-purple); }
.text-gray { color: var(--duo-gray-200); }

/* 
=========================================
Pricing Section
=========================================
*/
.pricing-cards {
    display: flex;
    justify-content: center;
    gap: 30px;
    flex-wrap: wrap;
    margin-top: 40px;
}

.pricing-card {
    background: white;
    border-radius: var(--radius-lg);
    border: 2px solid var(--duo-gray-100);
    padding: 40px 30px;
    width: 100%;
    max-width: 400px;
    position: relative;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    display: flex;
    flex-direction: column;
}

.pricing-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-lg);
}

.card-super:hover {
    border-color: var(--duo-super-blue);
}

.card-max:hover {
    border-color: var(--duo-max-purple);
}

.popular {
    transform: scale(1.05);
    border-color: var(--duo-max-purple);
    box-shadow: var(--shadow-md);
}

.popular:hover {
    transform: scale(1.05) translateY(-5px);
}

.popular-badge {
    position: absolute;
    top: -15px;
    left: 50%;
    transform: translateX(-50%);
    background: linear-gradient(90deg, #ff9600, #ffc800);
    color: white;
    padding: 5px 15px;
    border-radius: var(--radius-full);
    font-weight: 800;
    font-size: 14px;
    box-shadow: 0 4px 10px rgba(255, 150, 0, 0.3);
}

.card-header {
    margin-bottom: 20px;
}

.tier-logo {
    height: 90px;
    width: 90px;
    object-fit: cover;
    border-radius: var(--radius-md);
    margin-bottom: 10px;
}

.card-price {
    font-size: 48px;
    font-weight: 900;
    color: var(--duo-gray-800);
    margin-bottom: 30px;
    line-height: 1;
}

.card-price .currency {
    font-size: 24px;
    vertical-align: top;
    position: relative;
    top: 5px;
}

.card-price .period {
    font-size: 16px;
    color: var(--duo-gray-400);
    font-weight: 700;
}

.card-features {
    list-style: none;
    text-align: left;
    margin-bottom: 40px;
    flex: 1;
}

.card-features li {
    margin-bottom: 15px;
    font-size: 16px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.card-features li i {
    font-size: 18px;
    min-width: 25px;
}

.feature-disabled {
    color: var(--duo-gray-200);
    text-decoration: line-through;
}

/* 
=========================================
Feature Comparison Table
=========================================
*/
.table-responsive {
    overflow-x: auto;
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--duo-gray-100);
}

.feature-table {
    width: 100%;
    border-collapse: collapse;
    text-align: center;
}

.feature-table th, .feature-table td {
    padding: 20px;
    border-bottom: 1px solid var(--duo-gray-100);
}

.feature-table th {
    font-size: 20px;
    font-weight: 800;
    background-color: #fafafa;
}

.feature-table td:first-child, .feature-table th:first-child {
    text-align: left;
    font-weight: 700;
    width: 40%;
}

.feature-table tfoot td {
    border-bottom: none;
}

.col-super { color: var(--duo-super-blue-dark); }
.col-max { color: var(--duo-max-purple-dark); }

.highlight-row {
    background-color: rgba(194, 80, 231, 0.05);
}

.ai-badge {
    background: linear-gradient(45deg, var(--duo-super-blue), var(--duo-max-purple));
    color: white;
    font-size: 11px;
    padding: 2px 6px;
    border-radius: 4px;
    margin-right: 5px;
    vertical-align: middle;
}

/* 
=========================================
Guide Section
=========================================
*/
.steps-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 30px;
    margin-top: 50px;
}

.step-card {
    background: white;
    padding: 40px 20px;
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: var(--shadow-sm);
    position: relative;
    border: 2px solid transparent;
    transition: all 0.3s ease;
}

.step-card:hover {
    border-color: var(--duo-green);
    transform: translateY(-5px);
}

.step-number {
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    width: 40px;
    height: 40px;
    background: var(--duo-green);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 900;
    font-size: 20px;
    border: 4px solid white;
}

.step-icon {
    font-size: 48px;
    color: var(--duo-super-blue);
    margin-bottom: 20px;
    margin-top: 10px;
}

.step-card h3 {
    font-size: 20px;
    margin-bottom: 10px;
}

.step-card p {
    font-size: 15px;
    color: var(--duo-gray-400);
}

/* 
=========================================
FAQ Section
=========================================
*/
.faq-container {
    max-width: 800px;
}

.faq-list {
    margin-top: 40px;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.faq-item {
    background: white;
    border-radius: var(--radius-md);
    border: 2px solid var(--duo-gray-100);
    overflow: hidden;
    transition: all 0.3s ease;
}

.faq-question {
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    font-weight: 700;
    color: var(--duo-gray-800);
    transition: background-color 0.2s ease;
}

.faq-question:hover {
    background-color: #fafafa;
}

.faq-question h4 {
    margin: 0;
    font-size: 18px;
}

.faq-question i {
    transition: transform 0.3s ease;
    color: var(--duo-gray-400);
}

.faq-item.active {
    border-color: var(--duo-super-blue);
}

.faq-item.active .faq-question i {
    transform: rotate(180deg);
    color: var(--duo-super-blue);
}

.faq-answer {
    padding: 0 20px;
    max-height: 0;
    overflow: hidden;
    transition: all 0.3s ease;
    color: var(--duo-gray-400);
}

.faq-item.active .faq-answer {
    padding: 0 20px 20px;
    max-height: 500px; /* arbitrary max height for animation */
}

/* 
=========================================
Footer
=========================================
*/
.footer {
    background-color: var(--bg-night);
    color: white;
    padding: 60px 0 20px;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    gap: 40px;
    margin-bottom: 40px;
}

.footer-info {
    flex: 2;
}

.footer-info .logo {
    margin-bottom: 20px;
}

.footer-info p {
    color: #afafaf;
    max-width: 400px;
}

.footer-contact {
    flex: 1;
}

.footer-contact h3 {
    color: white;
    margin-bottom: 20px;
}

.footer-contact p {
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    gap: 10px;
    color: #afafaf;
}

.footer-contact a {
    color: white;
}

.footer-contact a:hover {
    color: var(--duo-green);
}

.footer-bottom {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid rgba(255,255,255,0.1);
    color: #777;
    font-size: 14px;
}

/* 
=========================================
Responsive
=========================================
*/
@media (max-width: 900px) {
    .desktop-nav {
        display: none;
    }
    .nav-actions {
        display: none;
    }
    
    .hero-content {
        flex-direction: column;
        text-align: center;
        padding-top: 20px;
    }
    
    .hero-text h1 {
        font-size: 36px;
    }
    
    .hero-buttons {
        justify-content: center;
    }
    
    .steps-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .pricing-card.popular {
        transform: scale(1);
    }
    .pricing-card.popular:hover {
        transform: translateY(-10px);
    }
}

@media (max-width: 600px) {
    .steps-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-content {
        flex-direction: column;
    }
    
    .feature-table td:first-child, .feature-table th:first-child {
        min-width: 150px;
    }
}