/* CSS Reset and Base Styles */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --secondary-color: #6b7280;
    --background: #f9fafb;
    --surface: #ffffff;
    --text-primary: #111827;
    --text-secondary: #6b7280;
    --border-color: #e5e7eb;
    --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-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --transition: 150ms ease;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* Container */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

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

/* Main Content */
main {
    flex: 1;
}

/* Editor Section */
.editor-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: 1.5rem;
    margin-bottom: 2rem;
}

#text-input {
    width: 100%;
    min-height: 200px;
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 1rem;
    line-height: 1.6;
    resize: vertical;
    transition: border-color var(--transition), box-shadow var(--transition);
}

#text-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

#text-input::placeholder {
    color: var(--text-secondary);
}

.editor-actions {
    display: flex;
    gap: 0.75rem;
    margin-top: 1rem;
    justify-content: flex-end;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.625rem 1.25rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    transition: all var(--transition);
}

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

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

.btn-secondary:active {
    transform: scale(0.98);
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: var(--surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    padding: 1.5rem;
    text-align: center;
    transition: transform var(--transition), box-shadow var(--transition);
}

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

.stat-value {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    line-height: 1.2;
    margin-bottom: 0.25rem;
}

.stat-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Keyword Section */
.keyword-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    padding: 1.5rem;
}

.keyword-section h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.keyword-description {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-bottom: 1rem;
}

.keyword-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.keyword-item {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--background);
    padding: 0.5rem 0.875rem;
    border-radius: 9999px;
    font-size: 0.875rem;
}

.keyword-word {
    font-weight: 500;
    color: var(--text-primary);
}

.keyword-count {
    color: var(--text-secondary);
    font-size: 0.75rem;
}

.keyword-density {
    color: var(--primary-color);
    font-weight: 600;
    font-size: 0.75rem;
}

.empty-state {
    color: var(--text-secondary);
    font-style: italic;
    padding: 1rem 0;
}

/* Footer */
footer {
    text-align: center;
    padding: 2rem 0 1rem;
    margin-top: auto;
}

footer p {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition);
}

footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 1.5rem 1rem;
    }

    header h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .editor-section {
        padding: 1rem;
    }

    #text-input {
        min-height: 150px;
        padding: 0.875rem;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .stat-card {
        padding: 1rem;
    }

    .stat-value {
        font-size: 1.5rem;
    }

    .stat-label {
        font-size: 0.75rem;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.75rem;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 0.75rem;
    }

    .stat-card {
        padding: 0.875rem;
    }

    .stat-value {
        font-size: 1.25rem;
    }

    .keyword-section {
        padding: 1rem;
    }

    .keyword-section h2 {
        font-size: 1.125rem;
    }
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus styles for keyboard navigation */
.btn:focus-visible,
#text-input:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --background: #111827;
        --surface: #1f2937;
        --text-primary: #f9fafb;
        --text-secondary: #9ca3af;
        --border-color: #374151;
    }

    .stat-card:hover {
        box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
    }

    .keyword-item {
        background: #374151;
    }
}