/* ===== CSS Variables ===== */
:root {
    /* Colors - Light Mode */
    --color-primary: #3b82f6;
    --color-primary-dark: #2563eb;
    --color-primary-light: #60a5fa;
    --color-secondary: #8b5cf6;
    --color-accent: #06b6d4;
    
    --color-bg: #ffffff;
    --color-bg-secondary: #f8fafc;
    --color-bg-tertiary: #f1f5f9;
    
    --color-text: #1e293b;
    --color-text-secondary: #64748b;
    --color-text-muted: #94a3b8;
    
    --color-border: #e2e8f0;
    --color-border-light: #f1f5f9;
    
    --color-success: #10b981;
    --color-warning: #f59e0b;
    --color-error: #ef4444;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
    
    /* Font */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans KR', sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    --font-size-4xl: 2.25rem;
    
    /* Container */
    --container-max-width: 1200px;
    --header-height: 64px;
}

/* Dark Mode */
[data-theme="dark"] {
    --color-bg: #0f172a;
    --color-bg-secondary: #1e293b;
    --color-bg-tertiary: #334155;
    
    --color-text: #f1f5f9;
    --color-text-secondary: #94a3b8;
    --color-text-muted: #64748b;
    
    --color-border: #334155;
    --color-border-light: #1e293b;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.3);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.4), 0 4px 6px -4px rgb(0 0 0 / 0.3);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.5), 0 8px 10px -6px rgb(0 0 0 / 0.4);
}

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

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

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);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

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

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

img {
    max-width: 100%;
    height: auto;
}

button {
    font-family: inherit;
    font-size: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

input, textarea, select {
    font-family: inherit;
    font-size: inherit;
}

ul, ol {
    list-style: none;
}

/* ===== Utilities ===== */
.container {
    width: 100%;
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--color-primary);
    color: white;
    z-index: 1000;
    transition: top var(--transition-fast);
}

.skip-link:focus {
    top: 0;
}

/* ===== Header ===== */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    height: var(--header-height);
    backdrop-filter: blur(10px);
}

.header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text);
}

.logo:hover {
    color: var(--color-primary);
}

.logo-icon {
    font-size: 1.5em;
}

.nav {
    display: flex;
    align-items: center;
}

.nav-toggle {
    display: none;
    width: 40px;
    height: 40px;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-md);
    background: var(--color-bg-secondary);
}

.hamburger {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--color-text);
    position: relative;
    transition: var(--transition-fast);
}

.hamburger::before,
.hamburger::after {
    content: '';
    position: absolute;
    width: 100%;
    height: 2px;
    background: var(--color-text);
    transition: var(--transition-fast);
}

.hamburger::before {
    top: -6px;
}

.hamburger::after {
    top: 6px;
}

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

.nav-link {
    color: var(--color-text-secondary);
    font-weight: 500;
    padding: var(--spacing-sm) 0;
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--color-primary);
    transition: width var(--transition-fast);
}

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

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.theme-toggle {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-full);
    background: var(--color-bg-secondary);
    transition: background-color var(--transition-fast), transform var(--transition-fast);
}

.theme-toggle:hover {
    background: var(--color-bg-tertiary);
    transform: rotate(15deg);
}

.theme-icon {
    font-size: 1.25rem;
}

/* ===== Hero Section ===== */
.hero {
    padding: var(--spacing-3xl) 0;
    background: linear-gradient(135deg, var(--color-bg-secondary) 0%, var(--color-bg) 100%);
    text-align: center;
}

.hero h1 {
    font-size: var(--font-size-4xl);
    font-weight: 800;
    margin-bottom: var(--spacing-md);
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

.search-container {
    max-width: 500px;
    margin: 0 auto;
    position: relative;
}

.search-input {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-lg);
    padding-right: 50px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-full);
    background: var(--color-bg);
    color: var(--color-text);
    font-size: var(--font-size-base);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.search-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.search-input::placeholder {
    color: var(--color-text-muted);
}

.search-btn {
    position: absolute;
    right: 8px;
    top: 50%;
    transform: translateY(-50%);
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-primary);
    color: white;
    border-radius: var(--radius-full);
    transition: background-color var(--transition-fast);
}

.search-btn:hover {
    background: var(--color-primary-dark);
}

/* ===== Categories Section ===== */
.categories {
    padding: var(--spacing-xl) 0;
}

.section-title {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-lg);
    text-align: center;
}

.category-tabs {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    justify-content: center;
}

.category-tab {
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-full);
    background: var(--color-bg-secondary);
    color: var(--color-text-secondary);
    font-weight: 500;
    transition: all var(--transition-fast);
    border: 2px solid transparent;
}

.category-tab:hover {
    background: var(--color-bg-tertiary);
    color: var(--color-text);
}

.category-tab.active {
    background: var(--color-primary);
    color: white;
}

/* ===== Tools Section ===== */
.tools-section {
    padding: var(--spacing-xl) 0 var(--spacing-3xl);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

.tool-card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.tool-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-secondary));
    transform: scaleX(0);
    transform-origin: left;
    transition: transform var(--transition-normal);
}

.tool-card:hover {
    border-color: var(--color-primary-light);
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.tool-card:hover::before {
    transform: scaleX(1);
}

.tool-card-link {
    display: block;
    color: inherit;
}

.tool-card-link:hover {
    color: inherit;
}

.tool-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.75rem;
    background: var(--color-bg-secondary);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-md);
}

.tool-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.tool-description {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    line-height: 1.5;
}

.tool-category-badge {
    display: inline-block;
    padding: var(--spacing-xs) var(--spacing-sm);
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-sm);
    font-size: var(--font-size-xs);
    color: var(--color-text-secondary);
    margin-top: var(--spacing-md);
}

.no-results {
    text-align: center;
    padding: var(--spacing-3xl);
    color: var(--color-text-secondary);
    font-size: var(--font-size-lg);
}

/* ===== About Section ===== */
.about {
    padding: var(--spacing-3xl) 0;
    background: var(--color-bg-secondary);
}

.about-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--spacing-lg);
}

.about-card {
    background: var(--color-bg);
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    text-align: center;
    border: 1px solid var(--color-border);
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.about-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

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

.about-card h3 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-sm);
}

.about-card p {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
}

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

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: var(--spacing-2xl);
    margin-bottom: var(--spacing-2xl);
}

.footer-brand {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.footer-brand .logo-icon,
.footer-brand .logo-text {
    display: inline;
}

.footer-description {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    margin-top: var(--spacing-sm);
}

.footer-links h4 {
    font-size: var(--font-size-base);
    font-weight: 600;
    margin-bottom: var(--spacing-md);
}

.footer-links ul {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

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

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

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

/* ===== Tool Page Styles ===== */
.tool-page {
    padding: var(--spacing-xl) 0 var(--spacing-3xl);
}

.tool-header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.tool-header h1 {
    font-size: var(--font-size-3xl);
    margin-bottom: var(--spacing-sm);
}

.tool-header p {
    color: var(--color-text-secondary);
    font-size: var(--font-size-lg);
}

.tool-container {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.tool-section {
    margin-bottom: var(--spacing-xl);
}

.tool-section:last-child {
    margin-bottom: 0;
}

.tool-section h2 {
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-md);
}

.tool-label {
    display: block;
    font-weight: 500;
    margin-bottom: var(--spacing-sm);
    color: var(--color-text);
}

.tool-textarea {
    width: 100%;
    min-height: 150px;
    padding: var(--spacing-md);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: var(--color-bg-secondary);
    color: var(--color-text);
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: var(--font-size-sm);
    resize: vertical;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.tool-textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.tool-input {
    width: 100%;
    padding: var(--spacing-md);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: var(--color-bg-secondary);
    color: var(--color-text);
    font-size: var(--font-size-base);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.tool-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.tool-select {
    width: 100%;
    padding: var(--spacing-md);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: var(--color-bg-secondary);
    color: var(--color-text);
    font-size: var(--font-size-base);
    cursor: pointer;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.tool-select:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

.tool-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-xl);
    background: var(--color-primary);
    color: white;
    border-radius: var(--radius-lg);
    font-weight: 600;
    transition: background-color var(--transition-fast), transform var(--transition-fast);
}

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

.tool-btn:active {
    transform: translateY(0);
}

.tool-btn-secondary {
    background: var(--color-bg-tertiary);
    color: var(--color-text);
}

.tool-btn-secondary:hover {
    background: var(--color-border);
}

.tool-btn-group {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.tool-output {
    background: var(--color-bg-tertiary);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    min-height: 100px;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: var(--font-size-sm);
    white-space: pre-wrap;
    word-break: break-all;
    position: relative;
}

.copy-btn {
    position: absolute;
    top: var(--spacing-sm);
    right: var(--spacing-sm);
    padding: var(--spacing-xs) var(--spacing-sm);
    background: var(--color-primary);
    color: white;
    border-radius: var(--radius-sm);
    font-size: var(--font-size-xs);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.tool-output:hover .copy-btn {
    opacity: 1;
}

.tool-info {
    background: var(--color-bg-secondary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.tool-info h3 {
    font-size: var(--font-size-base);
    margin-bottom: var(--spacing-sm);
}

.tool-info p {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    margin-bottom: var(--spacing-sm);
}

.tool-info ul {
    margin-left: var(--spacing-lg);
    list-style: disc;
}

.tool-info li {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    margin-bottom: var(--spacing-xs);
}

/* Grid layouts for tools */
.tool-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
}

.tool-grid-full {
    grid-column: 1 / -1;
}

/* Color picker specific */
.color-preview {
    width: 100%;
    height: 100px;
    border-radius: var(--radius-lg);
    border: 2px solid var(--color-border);
    margin-bottom: var(--spacing-md);
}

.color-input-group {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
}

.color-input-group input[type="color"] {
    width: 50px;
    height: 40px;
    padding: 0;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
}

/* QR Code specific */
.qr-preview {
    display: flex;
    justify-content: center;
    padding: var(--spacing-xl);
    background: white;
    border-radius: var(--radius-lg);
}

.qr-preview canvas,
.qr-preview img {
    max-width: 100%;
}

/* Toast notifications */
.toast {
    position: fixed;
    bottom: var(--spacing-xl);
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--color-text);
    color: var(--color-bg);
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-full);
    font-size: var(--font-size-sm);
    font-weight: 500;
    box-shadow: var(--shadow-xl);
    z-index: 1000;
    opacity: 0;
    transition: all var(--transition-normal);
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

.toast.success {
    background: var(--color-success);
}

.toast.error {
    background: var(--color-error);
}

/* Breadcrumb */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-lg) 0;
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
}

.breadcrumb a {
    color: var(--color-text-secondary);
}

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

.breadcrumb-separator {
    color: var(--color-text-muted);
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    :root {
        --font-size-4xl: 1.875rem;
        --font-size-3xl: 1.5rem;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .nav-menu {
        position: absolute;
        top: var(--header-height);
        left: 0;
        right: 0;
        background: var(--color-bg);
        border-bottom: 1px solid var(--color-border);
        flex-direction: column;
        padding: var(--spacing-lg);
        gap: var(--spacing-md);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-normal);
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .hero {
        padding: var(--spacing-2xl) 0;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        gap: var(--spacing-xl);
    }
    
    .tool-grid {
        grid-template-columns: 1fr;
    }
    
    .tool-btn-group {
        flex-direction: column;
    }
    
    .tool-btn {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }
    
    .category-tabs {
        justify-content: flex-start;
        overflow-x: auto;
        flex-wrap: nowrap;
        padding-bottom: var(--spacing-sm);
        -webkit-overflow-scrolling: touch;
    }
    
    .category-tab {
        flex-shrink: 0;
    }
    
    .tools-grid {
        grid-template-columns: 1fr;
    }
}

/* Print styles */
@media print {
    .header,
    .footer,
    .search-container,
    .category-tabs,
    .theme-toggle {
        display: none;
    }
    
    .tool-card {
        break-inside: avoid;
    }
}