/* CSS Custom Properties for Theming */
:root {
    --color-primary: #2563eb;
    --color-primary-dark: #1e40af;
    --color-secondary: #64748b;
    --color-background: #ffffff;
    --color-surface: #f8fafc;
    --color-text: #1e293b;
    --color-text-secondary: #475569;
    --color-border: #e2e8f0;
    --color-error: #dc2626;
    --color-success: #16a34a;

    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;

    --font-family-base: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-family-heading: Georgia, 'Times New Roman', 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;

    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;

    --border-radius-sm: 0.25rem;
    --border-radius-md: 0.5rem;
    --border-radius-lg: 0.75rem;

    --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-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);

    --transition-fast: 150ms ease-in-out;
    --transition-base: 200ms ease-in-out;
    --transition-slow: 300ms ease-in-out;

    --max-width-sm: 640px;
    --max-width-md: 768px;
    --max-width-lg: 1024px;
    --max-width-xl: 1280px;
}

/* Base Reset and Typography */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family-base);
    font-size: var(--font-size-base);
    line-height: var(--line-height-normal);
    color: var(--color-text);
    background-color: var(--color-background);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Typography Styles */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-family-heading);
    line-height: var(--line-height-tight);
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

h1 {
    font-size: var(--font-size-4xl);
    font-weight: 700;
}

h2 {
    font-size: var(--font-size-3xl);
    font-weight: 600;
}

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

h4 {
    font-size: var(--font-size-xl);
    font-weight: 500;
}

p {
    margin-bottom: var(--spacing-md);
    line-height: var(--line-height-relaxed);
}

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

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

a:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

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

/* Header Styling */
header {
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: var(--spacing-lg) 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.blog-title {
    margin: 0;
    font-size: var(--font-size-2xl);
    color: var(--color-primary);
}

nav ul {
    list-style: none;
    display: flex;
    gap: var(--spacing-lg);
    margin: 0;
}

nav li {
    margin: 0;
}

nav a {
    font-weight: 500;
    color: var(--color-text);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius-md);
    transition: background-color var(--transition-fast), color var(--transition-fast);
}

nav a:hover {
    background-color: var(--color-primary);
    color: white;
    text-decoration: none;
}

/* Main Content */
main {
    flex: 1;
    padding: var(--spacing-2xl) 0;
}

/* CSS Grid Layout for Feed Display */
.content-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.feed-item,
.blog-post {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    transition: box-shadow var(--transition-base), transform var(--transition-base);
}

.feed-item:hover,
.blog-post:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.feed-item h3,
.blog-post h3 {
    margin-bottom: var(--spacing-sm);
    font-size: var(--font-size-xl);
}

.feed-item-meta,
.blog-post-meta {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.feed-item-content,
.blog-post-content {
    color: var(--color-text);
    line-height: var(--line-height-relaxed);
}

.feed-item-link,
.blog-post-link {
    display: inline-block;
    margin-top: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-lg);
    background-color: var(--color-primary);
    color: white;
    border-radius: var(--border-radius-md);
    font-weight: 500;
    transition: background-color var(--transition-fast);
}

.feed-item-link:hover,
.blog-post-link:hover {
    background-color: var(--color-primary-dark);
    text-decoration: none;
}

/* Loading States */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-3xl) var(--spacing-md);
    color: var(--color-text-secondary);
}

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: var(--spacing-md);
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

.loading-text {
    font-size: var(--font-size-lg);
    font-weight: 500;
}

/* Error Message Styles */
.error {
    background-color: #fef2f2;
    border: 1px solid #fecaca;
    border-left: 4px solid var(--color-error);
    border-radius: var(--border-radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.error-title {
    color: var(--color-error);
    font-weight: 600;
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.error-title::before {
    content: '⚠';
    font-size: var(--font-size-xl);
}

.error-message {
    color: #991b1b;
    line-height: var(--line-height-relaxed);
    margin: 0;
}

.error-retry {
    margin-top: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-lg);
    background-color: var(--color-error);
    color: white;
    border: none;
    border-radius: var(--border-radius-md);
    font-weight: 500;
    cursor: pointer;
    transition: background-color var(--transition-fast);
}

.error-retry:hover {
    background-color: #b91c1c;
}

.error-retry:focus {
    outline: 2px solid var(--color-error);
    outline-offset: 2px;
}

/* Success Message Styles */
.success {
    background-color: #f0fdf4;
    border: 1px solid #bbf7d0;
    border-left: 4px solid var(--color-success);
    border-radius: var(--border-radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
    color: #166534;
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: var(--spacing-3xl) var(--spacing-md);
    color: var(--color-text-secondary);
}

.empty-state-icon {
    font-size: var(--font-size-4xl);
    margin-bottom: var(--spacing-md);
}

.empty-state-title {
    font-size: var(--font-size-2xl);
    color: var(--color-text);
    margin-bottom: var(--spacing-sm);
}

.empty-state-text {
    font-size: var(--font-size-lg);
}

/* Footer Styling */
footer {
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-xl) 0;
    margin-top: auto;
}

footer .container {
    text-align: center;
}

footer p {
    margin: 0;
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
}

/* Responsive Design - Tablet */
@media (min-width: 640px) {
    .content-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--spacing-xl);
    }

    header .container {
        flex-wrap: nowrap;
    }

    .blog-title {
        font-size: var(--font-size-3xl);
    }
}

/* Responsive Design - Desktop */
@media (min-width: 1024px) {
    .content-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .container {
        padding: 0 var(--spacing-xl);
    }

    main {
        padding: var(--spacing-3xl) 0;
    }

    header {
        padding: var(--spacing-xl) 0;
    }

    h1 {
        font-size: var(--font-size-4xl);
    }

    .feed-item,
    .blog-post {
        padding: var(--spacing-xl);
    }
}

/* Responsive Design - Large Desktop */
@media (min-width: 1280px) {
    .container {
        max-width: var(--max-width-xl);
    }
}

/* Mobile-First Accessibility Enhancements */
@media (max-width: 639px) {
    nav ul {
        flex-direction: row;
        gap: var(--spacing-sm);
    }

    nav a {
        padding: var(--spacing-xs) var(--spacing-sm);
        font-size: var(--font-size-sm);
    }

    .blog-title {
        font-size: var(--font-size-xl);
    }

    h1 {
        font-size: var(--font-size-2xl);
    }

    h2 {
        font-size: var(--font-size-xl);
    }

    h3 {
        font-size: var(--font-size-lg);
    }
}

/* Print Styles */
@media print {
    header,
    footer,
    nav {
        display: none;
    }

    .content-grid {
        grid-template-columns: 1fr;
    }

    .feed-item,
    .blog-post {
        page-break-inside: avoid;
    }
}

/* Reduced Motion Support */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* Dark Mode Support */
@media (prefers-color-scheme: dark) {
    :root {
        --color-primary: #3b82f6;
        --color-primary-dark: #60a5fa;
        --color-secondary: #94a3b8;
        --color-background: #0f172a;
        --color-surface: #1e293b;
        --color-text: #f1f5f9;
        --color-text-secondary: #cbd5e1;
        --color-border: #334155;
        --color-error: #ef4444;
        --color-success: #22c55e;
    }

    .error {
        background-color: #1e1b1b;
        border-color: #4c1d1d;
    }

    .error-message {
        color: #fca5a5;
    }

    .success {
        background-color: #0d1f15;
        border-color: #14532d;
        color: #86efac;
    }
}