/* ============================================
   CUONG NGUYEN - PORTFOLIO CSS
   Modern Design System with Glassmorphism
   ============================================ */

/* ============================================
   CSS VARIABLES - DESIGN TOKENS
   ============================================ */
:root {
    /* Colors - Modern Blue/Purple Palette */
    --primary: #3b82f6;
    --primary-light: #60a5fa;
    --primary-dark: #2563eb;
    --secondary: #8b5cf6;
    --secondary-light: #a78bfa;
    --accent: #ec4899;
    --accent-light: #f472b6;
    
    /* Backgrounds */
    --bg-dark: #0f172a;
    --bg-darker: #020617;
    --bg-card: #1e293b;
    --bg-card-hover: #334155;
    
    /* Glass Effects */
    --glass-bg: rgba(255, 255, 255, 0.05);
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-backdrop: blur(12px);
    
    /* Text Colors */
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;
    
    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 20px rgba(59, 130, 246, 0.3);
    
    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-display: 'Outfit', var(--font-sans);
    
    /* Z-Index */
    --z-base: 1;
    --z-dropdown: 100;
    --z-sticky: 200;
    --z-fixed: 300;
    --z-overlay: 400;
    --z-modal: 500;
}

/* ============================================
   RESET & BASE STYLES
   ============================================ */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

body {
    font-family: var(--font-sans);
    background-color: var(--bg-dark);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

/* ============================================
   BACKGROUND ELEMENTS
   ============================================ */
.background-gradient {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    background: 
        radial-gradient(circle at 20% 20%, rgba(59, 130, 246, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(139, 92, 246, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 50% 50%, rgba(236, 72, 153, 0.1) 0%, transparent 70%);
    animation: backgroundPulse 15s ease-in-out infinite;
}

@keyframes backgroundPulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.8; }
}

/* ============================================
   TYPOGRAPHY
   ============================================ */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-display);
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
}

h1 {
    font-size: clamp(2.5rem, 8vw, 4rem);
    background: linear-gradient(135deg, var(--text-primary) 0%, var(--text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

h2 {
    font-size: clamp(2rem, 5vw, 3rem);
}

h3 {
    font-size: clamp(1.5rem, 3vw, 2rem);
}

p {
    margin-bottom: var(--spacing-sm);
    color: var(--text-secondary);
}

a {
    color: var(--primary-light);
    text-decoration: none;
    transition: color var(--transition-base);
}

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

/* ============================================
   NAVIGATION
   ============================================ */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: var(--z-fixed);
    background: var(--glass-bg);
    backdrop-filter: var(--glass-backdrop);
    -webkit-backdrop-filter: var(--glass-backdrop);
    border-bottom: 1px solid var(--glass-border);
    padding: var(--spacing-sm) 0;
    transition: all var(--transition-base);
}

.navbar.scrolled {
    background: rgba(15, 23, 42, 0.9);
    box-shadow: var(--shadow-md);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    font-family: var(--font-display);
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
}

.nav-link {
    color: var(--text-secondary);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: all var(--transition-base);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--text-primary);
    background: var(--glass-bg);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 50%;
    transform: translateX(-50%);
    width: 50%;
    height: 2px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-radius: var(--radius-full);
}

/* Mobile Menu Toggle */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.nav-toggle span {
    display: block;
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    border-radius: var(--radius-full);
    transition: all var(--transition-base);
}

/* ============================================
   LAYOUT CONTAINERS
   ============================================ */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section {
    padding: var(--spacing-2xl) 0;
    min-height: 100vh;
    display: flex;
    align-items: center;
}

.section-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.section-title {
    margin-bottom: var(--spacing-sm);
}

.section-subtitle {
    color: var(--text-muted);
    font-size: 1.125rem;
}

/* ============================================
   CARDS & GLASS EFFECTS
   ============================================ */
.card {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-backdrop);
    -webkit-backdrop-filter: var(--glass-backdrop);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    transition: all var(--transition-base);
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(255, 255, 255, 0.2);
}

.card-glow {
    box-shadow: var(--shadow-glow);
}

/* ============================================
   BUTTONS
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: 1rem;
    border: none;
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: white;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.6);
}

.btn-secondary {
    background: var(--glass-bg);
    color: var(--text-primary);
    border: 1px solid var(--glass-border);
}

.btn-secondary:hover {
    background: var(--glass-border);
    border-color: rgba(255, 255, 255, 0.3);
}

.btn-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    border-radius: var(--radius-full);
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    color: var(--text-primary);
    transition: all var(--transition-base);
}

.btn-icon:hover {
    background: var(--primary);
    border-color: var(--primary);
    transform: scale(1.1);
}

/* ============================================
   GRID LAYOUTS
   ============================================ */
.grid {
    display: grid;
    gap: var(--spacing-lg);
}

.grid-2 {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

/* ============================================
   UTILITY CLASSES
   ============================================ */
.text-gradient {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.text-center {
    text-align: center;
}

.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }
.mb-xl { margin-bottom: var(--spacing-xl); }

.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }
.mt-xl { margin-top: var(--spacing-xl); }

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes float {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-10px);
    }
}

.fade-in {
    animation: fadeIn 0.6s ease-out forwards;
}

.float {
    animation: float 6s ease-in-out infinite;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */

/* Tablet */
@media (max-width: 1024px) {
    :root {
        font-size: 15px;
    }
    
    .section {
        min-height: auto;
        padding: var(--spacing-xl) 0;
    }
}

/* Mobile */
@media (max-width: 640px) {
    :root {
        font-size: 14px;
    }
    
    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        flex-direction: column;
        background: rgba(15, 23, 42, 0.98);
        backdrop-filter: var(--glass-backdrop);
        padding: var(--spacing-lg);
        gap: var(--spacing-md);
        transform: translateX(100%);
        transition: transform var(--transition-base);
        box-shadow: var(--shadow-lg);
    }
    
    .nav-menu.active {
        transform: translateX(0);
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .nav-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    
    .nav-toggle.active span:nth-child(2) {
        opacity: 0;
    }
    
    .nav-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(7px, -7px);
    }
    
    .grid-2,
    .grid-3 {
        grid-template-columns: 1fr;
    }
    
    .section {
        padding: var(--spacing-lg) 0;
    }
}

/* ============================================
   FOOTER
   ============================================ */
footer {
    text-align: center;
    padding: var(--spacing-xl) var(--spacing-md);
    background: var(--bg-darker);
    border-top: 1px solid var(--glass-border);
    color: var(--text-muted);
}

footer p {
    margin: 0;
}

/* ============================================
   SCROLL ANIMATIONS
   ============================================ */
.scroll-reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.6s ease-out;
}

.scroll-reveal.revealed {
    opacity: 1;
    transform: translateY(0);
}