/* ==========================================
   DESIGN SYSTEM - Anh-Thư G. Phan
   Last updated: December 14, 2025
   ========================================== */

/* ==========================================
   CSS VARIABLES
   ========================================== */
:root {
    /* Background & Surface */
    --bg: #070709;
    --surface: #0d0d12;
    --surface2: #14141c;

    /* Text */
    --text: #ffffff;
    --text-muted: #888888;
    --text-dim: #333333;

    /* Primary (Blue - True Rainbow Blue 240°) */
    --primary: #0000ff;
    --primary-light: #6666ff;
    --primary-dark: #000099;
    --primary-bg: rgba(0, 0, 255, 0.15);

    /* Human (Red/Coral) */
    --human: #ff6b6b;
    --human-light: #ff9999;
    --human-dark: #cc4444;
    --human-bg: rgba(255, 107, 107, 0.15);

    /* AI (Cyan/Teal) */
    --ai: #4ecdc4;
    --ai-light: #7eddda;
    --ai-dark: #2a9d8f;
    --ai-bg: rgba(78, 205, 196, 0.15);

    /* Synergy (Gold/Yellow - Human+AI together) */
    --synergy: #ffcc00;
    --synergy-light: #ffdd66;
    --synergy-dark: #997a00;
    --synergy-bg: rgba(255, 204, 0, 0.15);

    /* Secondary (Orange - Apps accent) */
    --secondary: #ff6600;
    --secondary-light: #ff9966;
    --secondary-dark: #993d00;

    /* Utility */
    --border: rgba(255, 255, 255, 0.08);
    --border-light: rgba(255, 255, 255, 0.15);

    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
}

/* ==========================================
   RESET & BASE
   ========================================== */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
    font-family: 'Inter', 'Be Vietnam Pro', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    min-height: 100vh;
}

/* ==========================================
   TYPOGRAPHY
   ========================================== */

/* Hero Title - Large page headings */
h1, .hero-title {
    font-size: clamp(2.5rem, 8vw, 5rem);
    font-weight: 900;
    letter-spacing: -0.04em;
    line-height: 1.1;
    margin-bottom: 1.5rem;
}

/* Section Title */
h2 {
    font-size: clamp(1.75rem, 4vw, 2.5rem);
    font-weight: 700;
    letter-spacing: -0.03em;
    line-height: 1.2;
    margin-bottom: 1rem;
}

/* Subsection Title */
h3 {
    font-size: clamp(1.2rem, 3vw, 1.5rem);
    font-weight: 700;
    letter-spacing: -0.02em;
    line-height: 1.3;
    margin-bottom: 0.75rem;
}

/* Subtitle / Tagline */
.subtitle, .hero-tagline {
    font-size: clamp(1rem, 2vw, 1.2rem);
    font-weight: 300;
    color: var(--text-muted);
    line-height: 1.8;
}

/* Accent text (colored) */
.accent { color: var(--primary); }
.accent-human { color: var(--human); }
.accent-ai { color: var(--ai); }
.accent-synergy { color: var(--synergy); }

/* ==========================================
   LAYOUT
   ========================================== */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 2rem;
}

.container-wide {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

/* ==========================================
   NAVIGATION (Desktop)
   ========================================== */
.nav-desktop {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    padding: 1.25rem 5vw;
    background: transparent;
    z-index: 1000;
}

.nav-desktop a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.85rem;
    font-weight: 500;
    transition: all 0.3s ease;
    background: rgba(7, 7, 9, 0.9);
    padding: 0.5rem 1rem;
    border-radius: 6px;
}

.nav-desktop a:hover { color: var(--text); }
.nav-desktop a.active { color: var(--primary); }

/* Nav Dropdown */
.nav-dropdown {
    position: relative;
}

.nav-dropdown-menu {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(13, 13, 18, 0.98);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 0.5rem;
    min-width: 180px;
    opacity: 0;
    visibility: hidden;
    transition: all 0.2s ease;
    margin-top: 0.5rem;
}

.nav-dropdown:hover .nav-dropdown-menu {
    opacity: 1;
    visibility: visible;
}

.nav-dropdown-menu a {
    display: block;
    padding: 0.5rem 0.75rem;
    border-radius: 4px;
    background: transparent;
    font-size: 0.8rem;
}

.nav-dropdown-menu a:hover {
    background: var(--primary-bg);
    color: var(--primary);
}

/* ==========================================
   HERO SECTION
   ========================================== */
.hero {
    min-height: 35vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    padding: 2rem 2rem 1.5rem;
    position: relative;
    overflow: hidden;
}

.hero-content {
    position: relative;
    z-index: 10;
    max-width: 800px;
}

.hero-eyebrow {
    font-size: 0.75rem;
    letter-spacing: 0.4em;
    text-transform: uppercase;
    color: var(--primary);
    margin-bottom: 1.5rem;
}

/* ==========================================
   CARDS
   ========================================== */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.5rem;
    transition: all 0.3s ease;
}

.card:hover {
    border-color: var(--border-light);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.card-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.card-subtitle {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 0.75rem;
}

.card-desc {
    font-size: 0.9rem;
    color: var(--text-muted);
    line-height: 1.6;
}

/* ==========================================
   BUTTONS
   ========================================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border-radius: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.3s ease;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--primary);
    color: var(--bg);
}

.btn-primary:hover {
    background: var(--primary-light);
    transform: translateY(-2px);
}

.btn-outline {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text);
}

.btn-outline:hover {
    border-color: var(--primary);
    color: var(--primary);
}

/* ==========================================
   TAGS / BADGES
   ========================================== */
.tag {
    display: inline-block;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.tag-human {
    background: var(--human-bg);
    color: var(--human);
}

.tag-ai {
    background: var(--ai-bg);
    color: var(--ai);
}

.tag-synergy {
    background: var(--synergy-bg);
    color: var(--synergy);
}

.tag-primary {
    background: var(--primary-bg);
    color: var(--primary);
}

/* ==========================================
   UTILITY CLASSES
   ========================================== */

/* Text alignment */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

/* Spacing */
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }

/* Flexbox */
.flex { display: flex; }
.flex-center { display: flex; justify-content: center; align-items: center; }
.flex-between { display: flex; justify-content: space-between; align-items: center; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }
.gap-3 { gap: 1.5rem; }

/* Grid */
.grid { display: grid; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-auto { grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }

/* ==========================================
   ANIMATIONS
   ========================================== */
@keyframes fadeUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.animate-fadeUp {
    opacity: 0;
    animation: fadeUp 0.8s ease forwards;
}

.animate-fadeIn {
    opacity: 0;
    animation: fadeIn 0.6s ease forwards;
}

/* Animation delays */
.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }

/* ==========================================
   RESPONSIVE
   ========================================== */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    .grid-2, .grid-3 {
        grid-template-columns: 1fr;
    }

    .nav-desktop {
        flex-wrap: wrap;
        gap: 0.25rem;
        padding: 0.75rem 1rem;
    }

    .nav-desktop a {
        font-size: 0.75rem;
        padding: 0.4rem 0.6rem;
    }
}

/* ==========================================
   PAGE-SPECIFIC COLOR OVERRIDES

   Each page can override --primary with its theme:
   - Apps: --primary: #ffcc00 (yellow)
   - Books: --primary: #ff6600 (orange)
   - CV: --primary: #3399ff (blue)
   - Synergy: --primary: #3399ff (blue)
   ========================================== */