/* --- CSS Variables --- */
:root {
    --bg-color: #FFFFFF;
    --text-color: #212121;
    --primary-color: #0d47a1; /* Dark Blue */
    --secondary-color: #1b5e20; /* Dark Green */
    --light-gray-bg: #f8f9fa;
    --code-bg: #f5f5f5;
    --border-color: #e0e0e0;
    --font-sans: 'Roboto', Arial, sans-serif;
    --font-mono: 'Fira Code', 'Courier New', monospace;
    --container-width: 1100px;
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 8px rgba(0,0,0,0.07);
}

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

body {
    font-family: var(--font-sans);
    color: var(--text-color);
    background-color: var(--bg-color);
    line-height: 1.7;
}

h1, h2, h3, h4 {
    font-weight: 700;
    line-height: 1.3;
    color: #111;
    margin-bottom: 1rem;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; border-bottom: 1px solid var(--border-color); padding-bottom: 0.5rem; margin-top: 2.5rem; }
h3 { font-size: 1.5rem; color: var(--secondary-color); }
h4 { font-size: 1.1rem; }

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.2s ease;
}
a:hover { color: var(--secondary-color); }

ul { list-style: none; }
ul li { margin-bottom: 0.5rem; }

.container {
    width: 100%;
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 1rem;
}

/* --- Header --- */
.site-header {
    background: rgba(255, 255, 255, 0.85); /* UI ENHANCEMENT: Translucent for a modern feel */
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(8px); /* UI ENHANCEMENT: Frosted glass effect */
}
.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-color);
}
.search-bar { display: none; }

/* --- Mobile Navigation --- */
.nav-toggle {
    display: block;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    z-index: 1001;
}
.hamburger {
    display: block;
    position: relative;
    width: 24px;
    height: 2px;
    background: var(--text-color);
    transition: all 0.3s ease-in-out; /* UI ENHANCEMENT: Smoother hamburger transition */
}
.hamburger::before, .hamburger::after {
    content: '';
    position: absolute;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--text-color);
    transition: all 0.3s ease-in-out;
}
.hamburger::before { top: -8px; }
.hamburger::after { top: 8px; }

.nav-links {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100vh;
    background: var(--bg-color);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    transform: translateX(100%);
    transition: transform 0.3s ease-in-out;
}
.nav-links a {
    font-size: 1.5rem;
    margin: 1rem 0;
    font-weight: 500;
}
/* Active state for mobile nav */
body.nav-open { overflow: hidden; } /* UI ENHANCEMENT: Prevent scrolling when nav is open */
body.nav-open .nav-links { transform: translateX(0); }
body.nav-open .hamburger { background: transparent; transform: rotate(135deg); }
body.nav-open .hamburger::before { top: 0; transform: rotate(90deg); }
body.nav-open .hamburger::after { top: 0; }

/* --- Hero Section --- */
.hero {
    padding: 4rem 0;
    text-align: center;
    background-color: var(--light-gray-bg);
    border-bottom: 1px solid var(--border-color);
}
.hero .subheadline {
    font-size: 1.1rem;
    max-width: 600px;
    margin: 0 auto 2rem;
    color: #555;
}
/* UI ENHANCEMENT: Button styles */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 6px; /* Slightly softer corners */
    font-weight: 500;
    border: 1px solid transparent;
    transition: all 0.2s ease;
    cursor: pointer;
}
.btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}
.btn-primary {
    background-color: var(--primary-color);
    color: var(--bg-color);
}
.btn-secondary {
    border-color: var(--primary-color);
    color: var(--primary-color);
    background-color: var(--bg-color);
}
.btn-secondary:hover { background-color: rgba(13, 71, 161, 0.05); }

/* --- Content & Cards --- */
.content-section:not(:first-child) { margin-top: 3rem; }
.card-grid {
    display: grid;
    gap: 1.5rem;
    grid-template-columns: 1fr;
    margin-top: 2rem;
}
.card {
    border: 1px solid var(--border-color); /* UI ENHANCEMENT: Removed hard border for shadow */
    box-shadow: var(--shadow-sm);
    border-radius: 6px;
    padding: 1.5rem;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.card:hover { /* UI ENHANCEMENT: Interactive card hover */
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}
.topics-grid .card { background-color: var(--light-gray-bg); text-align: center; }

/* --- Code Blocks & Tables --- */
.code-container {
    position: relative;
}
pre {
    background-color: var(--code-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 1.5rem 1rem 1rem;
    margin: 1rem 0;
    overflow-x: auto;
    font-size: 0.9rem;
}
code { font-family: var(--font-mono); }

/* UI ENHANCEMENT: Copy button for code blocks */
.copy-btn {
    position: absolute;
    top: 1.75rem;
    right: 0.75rem;
    background-color: #e0e0e0;
    border: none;
    color: #555;
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
    border-radius: 4px;
    cursor: pointer;
    opacity: 0.5;
    transition: all 0.2s ease;
}
.code-container:hover .copy-btn {
    opacity: 1;
}
.copy-btn:hover {
    background-color: #bdbdbd;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
}
th, td {
    text-align: left;
    padding: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}
th { background-color: var(--code-bg); font-weight: 500; }
tbody tr:hover { /* UI ENHANCEMENT: Table row hover */
    background-color: var(--light-gray-bg);
}

/* --- Sidebar & Forms --- */
.sidebar { margin-top: 3rem; }
.sidebar-widget {
    background-color: var(--light-gray-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}
.sidebar-widget h3 { margin-top: 0; font-size: 1.2rem; }
.sidebar-widget ul li a { display: block; padding: 0.25rem 0; }

/* UI ENHANCEMENT: Better form styling */
input, textarea {
    transition: all 0.2s ease;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 0.75rem;
    width: 100%;
    font-family: var(--font-sans);
    background-color: var(--bg-color);
}
input:focus, textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(13, 71, 161, 0.1);
}
.feedback-form textarea {
    min-height: 80px;
    margin-bottom: 0.5rem;
}
.feedback-form .btn { width: 100%; }

/* --- Footer --- */
.site-footer {
    background-color: #263238;
    color: #cfd8dc;
    padding: 3rem 0 1rem;
    margin-top: 4rem;
}
.site-footer a { color: #eceff1; }
.footer-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
}
.footer-column h4 { color: var(--bg-color); }
.footer-column a, .footer-column p {
    display: block;
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
}
.newsletter-signup input {
    border: 1px solid #546e7a;
    background: #37474f;
    color: var(--bg-color);
    margin-bottom: 0.5rem;
}
.newsletter-signup button {
    width: 100%;
    padding: 0.75rem;
    background: var(--primary-color);
    color: var(--bg-color);
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s ease;
}
.newsletter-signup button:hover { background-color: #0b3c8a; }

.footer-bottom {
    border-top: 1px solid #455a64;
    text-align: center;
    margin-top: 2rem;
    padding-top: 1rem;
    font-size: 0.9rem;
}

/* --- Desktop Styles --- */
@media (min-width: 992px) {
    h1 { font-size: 3rem; }
    .nav-toggle { display: none; }
    .nav-links {
        position: static;
        flex-direction: row;
        height: auto;
        transform: none;
        background: none;
        gap: 1.5rem;
    }
    .nav-links a { font-size: 1rem; margin: 0; }
    .search-bar { display: block; }
    .search-bar input {
        border-radius: 20px;
        padding: 0.5rem 1rem;
        min-width: 250px;
    }
    .search-bar button { display: none; }

    .main-content-area {
        display: grid;
        grid-template-columns: 1fr 280px;
        gap: 2.5rem;
        margin-top: 3rem;
    }
    .sidebar { margin-top: 2.5rem; }
    
    .card-grid { grid-template-columns: repeat(3, 1fr); }
    .topics-grid { grid-template-columns: repeat(2, 1fr); }
    .footer-grid { grid-template-columns: repeat(4, 1fr); }
}