CSS Sticky Navigation Bar | Sticky Navbar Tutorial

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Sticky Navigation - Example</title>
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
    <link rel="stylesheet" href="style.css">
    <script src="script.js" defer></script>
</head>
<body>
    <header class="web-header">
        <div class="header-content">
            <h1>Welcome to the CSS Tutorial</h1>
            <p>Scroll down to see the navigation bar transition.</p>
        </div>
    </header>

    <nav class="web-navbar" id="navbar">
        <div class="web-nav-content">
            <div class="web-brand">TUTORIAL</div>
            <div class="web-nav-links">
                <a href="#" class="active">Home</a>
                <a href="#">About Us</a>
                <a href="#">Services</a>
                <a href="#">Portfolio</a>
                <a href="#">Contact</a>
            </div>
            <div class="web-search-box">
                <input type="text" placeholder="Search..." aria-label="Search">
            </div>
        </div>
    </nav>

    <main class="web-content">
        <section class="web-section">
            <h2>HTML and CSS Basics</h2>
            <p>HTML (Hyper Text Markup Language) is the standard markup language for documents designed to be displayed in a 
            web browser. CSS (Cascading Style Sheets) is a style sheet language used for describing the 
            presentation of a document written in HTML or XML.</p>
        </section>

        <section class="web-section">
            <h2>JavaScript Programming</h2>
            <p>JavaScript is a high-level, interpreted programming language used to create 
            interactive effects within web browsers. Along with HTML and CSS, it forms the core of modern web technologies.</p>
        </section>

        <section class="web-section">
            <h2>Responsive Design</h2>
            <p>Responsive design is an approach to web design that makes web pages render well on a variety of devices and window 
            or screen sizes. This is crucial for modern web development.</p>
        </section>

        <section class="web-section">
            <h2>Web Security</h2>
            <p>Web security is of paramount importance when developing modern web applications. It involves various techniques 
            and methodologies to safeguard data and users.</p>
        </section>

        <section class="web-section">
            <h2>Performance Optimization</h2>
            <p>Web performance optimization is the process of improving website loading speeds and responsiveness. 
            This encompasses techniques such as code minification, image optimization, and efficient caching.</p>
        </section>
    </main>
</body>
</html>

:root {
    --primary: #007bff;
    --primary-dark: #0056b3;
    --text-main: var(--fg, #2c3e50);
    --bg-card: var(--card, #ffffff);
    --border-color: var(--border, #e2e8f0);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg, #f8fafc);
    color: var(--text-main);
}

.web-header {
    min-height: 50vh;
    /* Modern gradient with smooth color transition */
    background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
    color: #ffffff;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 2rem;
}

.header-content h1 {
    font-size: 3rem;
    font-weight: 800;
    letter-spacing: -0.03em;
    margin-bottom: 10px;
}

.header-content p {
    font-size: 1.2rem;
    opacity: 0.8;
}

.web-navbar {
    background-color: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    padding: 15px 30px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.web-brand {
    font-weight: 800;
    font-size: 1.2rem;
    letter-spacing: 1px;
    color: var(--primary);
}

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

.web-nav-links {
    display: flex;
    gap: 0.5rem;
}

.web-nav-links a {
    color: var(--text-main);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.95rem;
    transition: all 0.2s ease;
    padding: 8px 16px;
    border-radius: 20px;
}

.web-nav-links a:hover, .web-nav-links a.active {
    color: var(--primary);
    background-color: rgba(0, 123, 255, 0.08);
}

.web-search-box input {
    padding: 8px 16px;
    border: 1px solid var(--border-color);
    background: var(--bg, #f1f5f9);
    border-radius: 20px;
    outline: none;
    transition: all 0.3s ease;
    width: 200px;
    font-size: 0.9rem;
}

.web-search-box input:focus {
    border-color: var(--primary);
    background: var(--bg-card);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.15);
}

/* Styles for the sticky class toggled via JavaScript */
.is-sticky {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
    background-color: var(--bg-card);
    padding: 10px 30px; /* Slightly compacts the layout padding for better feel */
    animation: slideDownAnimation 0.3s ease;
}

@keyframes slideDownAnimation {
    from { transform: translateY(-100%); }
    to { transform: translateY(0); }
}

.web-content {
    max-width: 850px;
    margin: 3rem auto;
    padding: 0 20px;
}

.web-section {
    margin-bottom: 2.5rem;
    padding: 2.5rem;
    border-radius: 12px;
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 6px rgba(0,0,0,0.02);
}

.web-section h2 {
    color: var(--primary);
    margin-bottom: 1rem;
    font-weight: 700;
}

.web-section p {
    font-size: 1.05rem;
    line-height: 1.7;
    opacity: 0.9;
}

@media (max-width: 768px) {
    .web-nav-content {
        flex-direction: column;
        gap: 15px;
    }
    .web-nav-links {
        width: 100%;
        justify-content: center;
        flex-wrap: wrap;
    }
    .web-search-box {
        display: none; /* Hide search input on mobile layout viewports */
    }
}

document.addEventListener("DOMContentLoaded", function() {
    const navbar = document.getElementById("navbar");
    if (!navbar) return;

    // Crucial: Cache the initial viewport offset top position of the navbar once DOM is parsed!
    const stickyTop = navbar.offsetTop;

    function handleScroll() {
        // Evaluate the current vertical scroll displacement offset
        if (window.pageYOffset >= stickyTop) {
            navbar.classList.add("is-sticky");
            // Dynamically introduce body padding-top placeholder to counteract structural layout layout shifts
            document.body.style.paddingTop = navbar.offsetHeight + "px";
        } else {
            navbar.classList.remove("is-sticky");
            // Reset layout structural adjustments when navigation drops back into position flow
            document.body.style.paddingTop = "0px";
        }
    }

    // Attach windows scrolling event capture handler
    window.addEventListener("scroll", handleScroll);

    // Click behavior management and active state styling toggle routine
    const links = document.querySelectorAll(".web-nav-links a");
    links.forEach(link => {
        link.addEventListener("click", function(e) {
            e.preventDefault();
            links.forEach(l => l.classList.remove("active"));
            this.classList.add("active");
        });
    });
});