:root {
    /* Color Palette */
    --bg-primary: #0f1115;
    --bg-secondary: #1a1d24;
    --bg-tertiary: #232730;
    
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    
    --accent-primary: #6366f1; /* Indigo */
    --accent-primary-hover: #4f46e5;
    --accent-secondary: #8b5cf6; /* Violet */
    
    --border-color: rgba(255, 255, 255, 0.08);
    --border-color-hover: rgba(255, 255, 255, 0.15);
    
    --error: #ef4444;
    --success: #10b981;
    
    /* Layout & Spacing */
    --max-width: 1200px;
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.15);
    
    --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="light"] {
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f5f9;
    
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    
    --border-color: rgba(0, 0, 0, 0.1);
    --border-color-hover: rgba(0, 0, 0, 0.2);
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.15);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
    -webkit-font-smoothing: antialiased;
}

a {
    color: inherit;
    text-decoration: none;
}

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

/* Layout */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* Header */
.header {
    position: sticky;
    top: 0;
    z-index: 50;
    background-color: rgba(15, 17, 21, 0.7);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
}

[data-theme="light"] .header {
    background-color: rgba(255, 255, 255, 0.8);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 4rem;
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.nav-links {
    display: flex;
    gap: 1.5rem;
    align-items: center;
}

.nav-links a {
    font-size: 0.95rem;
    color: var(--text-secondary);
    font-weight: 500;
    transition: var(--transition);
}

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

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.theme-toggle:hover {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

/* Hero Section */
.hero {
    padding: 5rem 0 3rem;
    text-align: center;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 1rem;
    letter-spacing: -0.025em;
}

.hero p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* Grid Layout */
.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    padding: 2rem 0 5rem;
}

.tool-card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    gap: 1rem;
    position: relative;
    overflow: hidden;
}

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

.tool-card-icon {
    width: 3rem;
    height: 3rem;
    background: linear-gradient(135deg, rgba(99,102,241,0.1), rgba(139,92,246,0.1));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-primary);
}

.tool-card-title {
    font-size: 1.125rem;
    font-weight: 600;
}

.tool-card-desc {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* AdSense Placeholders */
.ad-container {
    width: 100%;
    margin: 2rem auto; /* margin: 0 auto를 유지하여 중앙 정렬 수정 */
    display: none; /* 애드센스 승인 전에는 숨김 (승인 후 display: flex; 로 변경하세요) */
    justify-content: center;
    text-align: center;
}

.ad-placeholder {
    width: 100%;
    max-width: 728px;
    height: 90px;
    background-color: var(--bg-tertiary);
    border: 1px dashed var(--border-color);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* Tool Interface General */
.tool-header {
    padding: 3rem 0 2rem;
    text-align: center;
}

.tool-header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

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

.tool-workspace {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    margin-bottom: 5rem;
}

@media (min-width: 768px) {
    .tool-workspace.split {
        grid-template-columns: 1fr 1fr;
    }
}

.panel {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.panel-header {
    padding: 1rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: var(--bg-tertiary);
}

.panel-title {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.panel-actions {
    display: flex;
    gap: 0.5rem;
}

.btn {
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid transparent;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-icon {
    padding: 0.4rem;
}

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

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

.btn-ghost {
    background-color: transparent;
    color: var(--text-secondary);
}

.btn-ghost:hover {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

.panel-body {
    flex: 1;
    display: flex;
    flex-direction: column;
}

textarea, .textarea-like {
    width: 100%;
    min-height: 300px;
    padding: 1.5rem;
    background-color: transparent;
    border: none;
    color: var(--text-primary);
    font-family: 'Inter', sans-serif;
    font-size: 1rem;
    resize: vertical;
    outline: none;
}

textarea:focus {
    outline: none;
}

/* specific stats row for word counter */
.stats-row {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-bottom: 2rem;
}

@media (min-width: 640px) {
    .stats-row {
        grid-template-columns: repeat(4, 1fr);
    }
}

.stat-box {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    text-align: center;
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent-primary);
    line-height: 1;
    margin-bottom: 0.5rem;
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Footer */
.footer {
    border-top: 1px solid var(--border-color);
    padding: 3rem 0;
    margin-top: auto;
}

.footer-inner {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    text-align: center;
}

.footer-text {
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* Notification Toast */
.toast-container {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    z-index: 100;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.toast {
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transform: translateY(20px);
    opacity: 0;
    animation: slideIn 0.3s forwards, slideOut 0.3s forwards 3s;
}

@keyframes slideIn {
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

@keyframes slideOut {
    to {
        transform: translateY(20px);
        opacity: 0;
    }
}