/* =================================
   Dayangyu AI - Minimal Theme (Western Style)
   Inspired by OpenAI, SaveSora, Stripe
   ================================= */

/* ===== CSS Variables ===== */
:root {
    /* Colors - Dayangyu Green Theme (Light Mode) */
    --color-primary: #10a37f;
    --color-primary-hover: #0d8a6a;
    --color-secondary: #6e6e80;
    --color-text: #0d0d0d;
    --color-text-secondary: #6e6e80;
    --color-text-light: #acacbe;
    --color-bg: #ffffff;
    --color-bg-secondary: #f7f7f8;
    --color-bg-tertiary: #ffffff;
    --color-border: #ececf1;
    --color-border-light: #e5e5e5;
    --color-accent: #19c37d;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
    --font-size-xs: 0.75rem;      /* 12px */
    --font-size-sm: 0.875rem;     /* 14px */
    --font-size-base: 1rem;       /* 16px */
    --font-size-lg: 1.125rem;     /* 18px */
    --font-size-xl: 1.25rem;      /* 20px */
    --font-size-2xl: 1.5rem;      /* 24px */
    --font-size-3xl: 1.875rem;    /* 30px */
    --font-size-4xl: 2.25rem;     /* 36px */
    --font-size-5xl: 3rem;        /* 48px */
    --font-size-6xl: 3.75rem;     /* 60px */
    
    /* Spacing */
    --spacing-xs: 0.5rem;         /* 8px */
    --spacing-sm: 0.75rem;        /* 12px */
    --spacing-md: 1rem;           /* 16px */
    --spacing-lg: 1.5rem;         /* 24px */
    --spacing-xl: 2rem;           /* 32px */
    --spacing-2xl: 3rem;          /* 48px */
    --spacing-3xl: 4rem;          /* 64px */
    --spacing-4xl: 6rem;          /* 96px */
    
    /* Border Radius */
    --radius-sm: 0.375rem;        /* 6px */
    --radius-md: 0.5rem;          /* 8px */
    --radius-lg: 0.75rem;         /* 12px */
    --radius-xl: 1rem;            /* 16px */
    --radius-full: 9999px;
    
    /* Shadows - Very subtle */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -1px rgba(0, 0, 0, 0.03);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.05), 0 4px 6px -2px rgba(0, 0, 0, 0.03);
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 200ms ease;
    --transition-slow: 300ms ease;
    
    /* Layout */
    --container-width: 1200px;
    --navbar-height: 64px;
}

/* Dark Mode Variables */
[data-theme="dark"] {
    --color-primary: #19c37d;
    --color-primary-hover: #1ea872;
    --color-secondary: #6e6e80;
    --color-text: #ececf1;
    --color-text-secondary: #c5c5d2;
    --color-text-light: #8e8ea0;
    --color-bg: #0d0d0d;
    --color-bg-secondary: #1a1a1a;
    --color-bg-tertiary: #202020;
    --color-border: #2d2d2d;
    --color-border-light: #3d3d3d;
    --color-accent: #19c37d;
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-bg);
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    color: var(--color-text);
}

h1 {
    font-size: var(--font-size-5xl);
    font-weight: 700;
    letter-spacing: -0.02em;
}

h2 {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    letter-spacing: -0.01em;
}

h3 {
    font-size: var(--font-size-2xl);
    font-weight: 600;
}

p {
    color: var(--color-text-secondary);
}

a {
    color: inherit;
    text-decoration: none;
    transition: color var(--transition-fast);
}

/* ===== Container ===== */
.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 var(--spacing-xl);
}

/* ===== Navigation ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--navbar-height);
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
    transition: all var(--transition-base);
}

[data-theme="dark"] .navbar {
    background: rgba(13, 13, 13, 0.8);
}

.nav-wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--navbar-height);
}

.nav-brand {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text);
}

.logo-text {
    color: var(--color-text);
}

.nav-menu {
    display: flex;
    gap: var(--spacing-xl);
    align-items: center;
}

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

.nav-link:hover {
    color: var(--color-text);
    background: var(--color-bg-secondary);
}

.nav-link.active {
    color: var(--color-primary);
    background: var(--color-bg-secondary);
    font-weight: 600;
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

/* Language Switcher */
.language-switcher {
    position: relative;
}

.lang-btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-sm);
    background: transparent;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.lang-btn:hover {
    border-color: var(--color-text-secondary);
}

.lang-dropdown {
    position: absolute;
    top: calc(100% + var(--spacing-xs));
    right: 0;
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xs);
    min-width: 120px;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-base);
}

.language-switcher:hover .lang-dropdown,
.lang-dropdown:hover {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.lang-option {
    display: block;
    padding: var(--spacing-xs) var(--spacing-sm);
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.lang-option:hover {
    background: var(--color-bg-secondary);
    color: var(--color-text);
}

.lang-option.active {
    background: var(--color-bg-secondary);
    color: var(--color-text);
    font-weight: 600;
}

.lang-option.active:hover {
    background: var(--color-bg-secondary);
    color: var(--color-text);
}

/* Theme Toggle */
.theme-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: transparent;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.theme-toggle:hover {
    border-color: var(--color-text-secondary);
}

/* Mobile Toggle */
.mobile-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
}

.mobile-toggle span {
    width: 20px;
    height: 2px;
    background: var(--color-text);
    border-radius: var(--radius-full);
    transition: all var(--transition-fast);
}

/* ===== Hero Section ===== */
.hero {
    padding: calc(var(--navbar-height) + var(--spacing-4xl)) 0 var(--spacing-4xl);
    text-align: center;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
    line-height: 1.2;
    letter-spacing: -0.02em;
    margin-bottom: var(--spacing-lg);
    background: linear-gradient(135deg, var(--color-text) 0%, var(--color-text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    padding-right: 0.1em;
    display: inline-block;
}

.hero-subtitle {
    font-size: var(--font-size-xl);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-2xl);
    line-height: 1.6;
}

.hero-cta {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-sm) var(--spacing-xl);
    font-size: var(--font-size-base);
    font-weight: 500;
    border-radius: var(--radius-lg);
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

.btn-primary {
    background: var(--color-text);
    color: var(--color-bg);
    font-weight: 600;
}

.btn-primary:hover {
    background: var(--color-text-secondary);
    transform: translateY(-1px);
}

[data-theme="light"] .btn-primary {
    background: var(--color-text);
    color: var(--color-bg);
}

[data-theme="light"] .btn-primary:hover {
    background: var(--color-text-secondary);
}

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

.btn-secondary:hover {
    border-color: var(--color-text-secondary);
    transform: translateY(-1px);
}

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

.btn-outline:hover {
    background: var(--color-bg-secondary);
    border-color: var(--color-text-secondary);
}

/* ===== Features Section ===== */
.features {
    padding: var(--spacing-4xl) 0;
    background: var(--color-bg-secondary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-2xl);
}

.feature-card {
    padding: var(--spacing-xl);
    text-align: center;
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.feature-title {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text);
}

.feature-description {
    font-size: var(--font-size-base);
    color: var(--color-text-secondary);
    line-height: 1.7;
}

/* ===== Products Section ===== */
.products {
    padding: var(--spacing-4xl) 0;
}

.section-header {
    text-align: center;
    margin-bottom: var(--spacing-3xl);
}

.section-title {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

.section-subtitle {
    font-size: var(--font-size-lg);
    color: var(--color-text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

.products-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-xl);
}

.product-card {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    transition: all var(--transition-base);
}

.product-card:hover {
    border-color: var(--color-text-secondary);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
    transform: translateY(-4px);
    background: var(--color-bg-tertiary);
}

[data-theme="light"] .product-card {
    background: var(--color-bg);
}

[data-theme="light"] .product-card:hover {
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
    border-color: var(--color-text-light);
}

.product-header {
    margin-bottom: var(--spacing-lg);
}

.product-icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-md);
}

.product-name {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
    color: var(--color-text);
}

.product-tagline {
    font-size: var(--font-size-sm);
    color: var(--color-text-light);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.product-description {
    font-size: var(--font-size-base);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.7;
}

.product-features {
    list-style: none;
    margin-bottom: var(--spacing-xl);
}

.product-features li {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-lg);
    position: relative;
}

.product-features li::before {
    content: "→";
    position: absolute;
    left: 0;
    color: var(--color-text-secondary);
    font-weight: 600;
}

.product-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--color-text);
    transition: all var(--transition-fast);
}

.product-link:hover {
    gap: var(--spacing-sm);
    color: var(--color-text-secondary);
}

/* ===== Use Cases Section ===== */
.use-cases {
    padding: var(--spacing-4xl) 0;
    background: var(--color-bg-secondary);
}

.use-cases-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-xl);
}

.use-case-card {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    transition: all var(--transition-base);
}

.use-case-card:hover {
    border-color: var(--color-text-secondary);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
    transform: translateY(-2px);
    background: var(--color-bg-tertiary);
}

[data-theme="light"] .use-case-card {
    background: var(--color-bg);
}

[data-theme="light"] .use-case-card:hover {
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
    border-color: var(--color-text-light);
}

.use-case-title {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text);
}

.use-case-description {
    font-size: var(--font-size-base);
    color: var(--color-text-secondary);
    line-height: 1.7;
}

/* ===== CTA Section ===== */
.cta-section {
    padding: var(--spacing-4xl) 0;
    text-align: center;
}

.cta-content {
    max-width: 700px;
    margin: 0 auto;
}

.cta-title {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

.cta-description {
    font-size: var(--font-size-lg);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-2xl);
}

.cta-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== Footer ===== */
.footer {
    background: var(--color-bg-secondary);
    padding: var(--spacing-3xl) 0 var(--spacing-xl);
    border-top: 1px solid var(--color-border);
}

.footer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-2xl);
    margin-bottom: var(--spacing-2xl);
}

.footer-heading {
    font-size: var(--font-size-sm);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: var(--spacing-xs);
}

.footer-links a {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: var(--color-text);
}

.footer a {
    color: var(--color-text-secondary);
    transition: color var(--transition-fast);
}

.footer a:hover {
    color: var(--color-text);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-xl);
    border-top: 1px solid var(--color-border);
}

.footer-text,
.footer-copyright {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    margin: var(--spacing-xs) 0;
}

/* ===== Feature Cards Enhancement ===== */
.feature-card {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    transition: all var(--transition-base);
}

.feature-card:hover {
    border-color: var(--color-text-secondary);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
    background: var(--color-bg-tertiary);
}

[data-theme="light"] .feature-card {
    background: var(--color-bg);
}

[data-theme="light"] .feature-card:hover {
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
    border-color: var(--color-text-light);
}

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

.animate-in {
    animation: fadeInUp 0.6s ease-out forwards;
    opacity: 0;
}

/* ===== Responsive Enhancements ===== */
@media (max-width: 768px) {
    .hero-title {
        font-size: 2.5rem;
        display: block;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .products-grid,
    .features-grid,
    .use-cases-grid {
        grid-template-columns: 1fr;
    }
}