:root {
    /* Dark Mode (Default) */
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --bg-card: linear-gradient(to bottom, #1e293b, #0f172a);
    --text-primary: #ffffff;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --border-color: #334155;
    --accent-color: #3b82f6;
    --accent-light: #60a5fa;
}

body.light-mode {
    --bg-primary: #f8fafc;
    --bg-secondary: #f1f5f9;
    --bg-tertiary: #e2e8f0;
    --bg-card: linear-gradient(to bottom, #ffffff, #f8fafc);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #64748b;
    --border-color: #cbd5e1;
    --accent-color: #2563eb;
    --accent-light: #3b82f6;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    min-height: 100vh;
    color: var(--text-secondary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    transition: background-color 0.3s ease, color 0.3s ease;
}

::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--bg-tertiary);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.theme-toggle {
    background: var(--accent-color);
    color: white;
    border: 2px solid var(--accent-light);
    border-radius: 50%;
    width: 38px;
    height: 38px;
    font-size: 1.1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
    margin-left: 30px;
}

.theme-toggle:hover {
    transform: scale(1.15) rotate(20deg);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.4);
    background: var(--accent-light);
}

.theme-toggle:active {
    transform: scale(0.95);
}

header {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    padding: 12px 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
}

header a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.3s ease;
}

header a:hover {
    color: var(--accent-light);
}

nav {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

footer {
    text-align: center;
    padding: 30px 20px;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    margin-top: 60px;
}

.highlight {
    color: var(--accent-light);
    font-weight: 600;
}

/* Article page styles */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 40px 20px;
}

.nav-back {
    display: inline-block;
    margin-bottom: 30px;
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 600;
}

.nav-back:hover {
    text-decoration: underline;
}

.article-header {
    margin-bottom: 40px;
}

.article-header h1 {
    font-size: 2.5rem;
    color: var(--text-primary);
    margin-bottom: 15px;
    line-height: 1.2;
}

.article-meta {
    display: flex;
    gap: 15px;
    color: var(--text-muted);
    font-size: 0.875rem;
    align-items: center;
}

.article-tag {
    background: var(--border-color);
    padding: 4px 10px;
    border-radius: 20px;
    color: var(--accent-light);
}

.article-body {
    color: var(--text-secondary);
    line-height: 1.8;
    font-size: 1.05rem;
}

.article-body h2 {
    font-size: 1.8rem;
    color: var(--text-primary);
    margin-top: 35px;
    margin-bottom: 15px;
}

.article-body h3 {
    font-size: 1.3rem;
    color: var(--text-primary);
    margin-top: 25px;
    margin-bottom: 12px;
}

.article-body p {
    margin-bottom: 15px;
}

.article-body ul {
    margin-left: 20px;
    margin-bottom: 15px;
}

.article-body li {
    margin-bottom: 10px;
}