/* ============================================================
   GLOBAL THEME – TECHNOLOGY BLUE (Option C)
   Clean • Modern • Responsive • Fast • Professional
============================================================ */

:root {
    --blue: #0058cc;
    --blue-dark: #003c8a;
    --blue-light: #e7f0ff;
    --text-dark: #222;
    --text-light: #fff;
    --gray: #f4f4f4;
    --gray-dark: #ddd;
    --shadow: 0 4px 20px rgba(0,0,0,0.1);
    --radius: 10px;
    font-family: "Segoe UI", Tahoma, sans-serif;
}


/* =========================
      GLOBAL RESET
========================= */

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

body {
    background: #fff;
    color: var(--text-dark);
    line-height: 1.7;
}

/* =========================
      HEADER SECTION
========================= */

.header-logo {
    display: flex;
    align-items: center;
    gap: 20px;
    padding: 25px;
    background: var(--blue);
    color: var(--text-light);
    box-shadow: var(--shadow);
}

.site-logo {
    width: 90px;
    height: auto;
}

.header-text h1 {
    font-size: 2.2rem;
    font-weight: bold;
}

.header-text p {
    font-size: 1.1rem;
    opacity: 0.9;
}

/* =========================
      NAVIGATION BAR
========================= */

nav {
    background: var(--blue-dark);
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    gap: 25px;
    padding: 14px;
}

nav ul li a {
    text-decoration: none;
    color: var(--text-light);
    font-size: 1rem;
    padding: 10px 15px;
    transition: 0.2s;
}

nav ul li a:hover,
nav ul li a.active {
    background: var(--blue);
    border-radius: 5px;
}

/* =========================
     MAIN CONTENT AREA
========================= */

section, .lesson-content, .contact-container {
    max-width: 900px;
    margin: auto;
    padding: 25px;
}

/* =========================
        SIDEBAR
========================= */

.course-container {
    display: flex;
    gap: 30px;
    padding: 25px;
}

.sidebar {
    width: 250px;
    background: var(--blue-light);
    padding: 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    position: sticky;
    top: 20px;
    height: fit-content;
}

.sidebar h3 {
    margin-bottom: 15px;
    font-size: 1.2rem;
}

.sidebar ul {
    list-style: none;
}

.sidebar ul li {
    margin-bottom: 12px;
}

.sidebar ul li a {
    text-decoration: none;
    color: var(--blue-dark);
    padding: 8px;
    display: block;
    border-radius: 6px;
    transition: 0.2s;
}

.sidebar ul li a:hover {
    background: var(--blue);
    color: white;
}

/* =========================
      LESSON CONTENT
========================= */

.lesson-content h2 {
    font-size: 2rem;
    margin-bottom: 15px;
}

.lesson-content h3 {
    margin-top: 25px;
    margin-bottom: 10px;
}

pre {
    background: #1e1e1e;
    color: #00e676;
    padding: 15px;
    border-radius: var(--radius);
    overflow-x: auto;
    margin: 20px 0;
}

/* =========================
      BUTTONS & NAVIGATION
========================= */

.lesson-nav {
    display: flex;
    justify-content: space-between;
    margin-top: 30px;
}

.lesson-nav a {
    text-decoration: none;
    padding: 10px 18px;
    background: var(--blue);
    color: white;
    border-radius: 6px;
    transition: 0.2s;
    box-shadow: var(--shadow);
}

.lesson-nav a:hover {
    background: var(--blue-dark);
}

.back-to-top {
    display: inline-block;
    margin-top: 20px;
    color: var(--blue-dark);
}

/* =========================
      CONTACT PAGE
========================= */

.contact-container {
    background: var(--gray);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.contact-container input,
.contact-container textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--gray-dark);
    border-radius: var(--radius);
}

.contact-container button {
    background: var(--blue);
    color: white;
    border: none;
    padding: 12px 18px;
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 1.1rem;
}

.contact-container button:hover {
    background: var(--blue-dark);
}

/* =========================
        FOOTER
========================= */

footer {
    background: var(--blue-dark);
    color: white;
    text-align: center;
    padding: 12px;
    margin-top: 50px;
}



/* ============================================================
   RESPONSIVENESS
============================================================ */

@media (max-width: 1000px) {
    .course-container {
        flex-direction: column;
    }
    .sidebar {
        width: 100%;
        position: static;
    }
}

@media (max-width: 600px) {
    nav ul {
        flex-wrap: wrap;
        gap: 10px;
    }
    .header-logo {
        flex-direction: column;
        text-align: center;
    }
    .site-logo {
        width: 70px;
    }
    .header-text h1 {
        font-size: 1.6rem;
    }
}