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

body {
    background: #071a33;
    color: #edf4fc;
    font-family: Arial, sans-serif;
    line-height: 1.7;
}

/* Header */

header {
    padding: 22px 8%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #203b5c;
}

.logo {
    font-size: 20px;
    font-weight: bold;
    letter-spacing: 1px;
}

.logo span {
    color: #61c4ed;
}

nav a {
    color: #c5d5e8;
    text-decoration: none;
    margin-left: 22px;
    font-size: 14px;
}

nav a:hover {
    color: #61c4ed;
}

/* Common Layout */

.container {
    width: 84%;
    max-width: 1100px;
    margin: auto;
}

/* Homepage Hero */

.hero {
    padding: 75px 0 60px;
}

.hero h1 {
    font-size: 42px;
    margin-bottom: 15px;
}

.hero p {
    color: #a9bdd4;
    max-width: 650px;
    font-size: 17px;
}

h2 {
    font-size: 27px;
    margin-bottom: 8px;
}

.subtitle {
    color: #a9bdd4;
    margin-bottom: 25px;
}

/* Course Catalogue */

.course-catalogue {
    display: block;
    margin: 25px 0 80px;
}

.course-category {
    margin-bottom: 45px;
}

.category-title {
    font-size: 22px;
    font-weight: bold;
    color: #61c4ed;
    margin-bottom: 18px;
    padding-bottom: 10px;
    border-bottom: 1px solid #244565;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.course-card {
    display: block;
    background: #102b4b;
    border: 1px solid #244565;
    padding: 25px;
    border-radius: 9px;
    color: white;
    text-decoration: none;
    transition: 0.2s;
}

.course-card:hover {
    border-color: #61c4ed;
    transform: translateY(-3px);
}

.course-card h3,
.course-card h4 {
    font-size: 18px;
    margin-bottom: 10px;
    color: #edf4fc;
}

.course-card p {
    color: #a9bdd4;
    font-size: 14px;
}

.course-status {
    display: inline-block;
    margin-top: 20px;
    color: #61c4ed;
    font-size: 12px;
    font-weight: bold;
}

.available-course {
    cursor: pointer;
}

.available-course:hover {
    background: #143557;
}

.coming-soon-course {
    opacity: 0.55;
    cursor: not-allowed;
}

.coming-soon-course .course-status {
    color: #f0c777;
}

/* Compatibility with Existing Course Cards */

.course-card .status {
    display: inline-block;
    margin-top: 20px;
    color: #61c4ed;
    font-size: 12px;
    font-weight: bold;
}

.course-card.disabled {
    opacity: 0.55;
    cursor: not-allowed;
}

.course-card .coming {
    color: #f0c777;
}

/* Course Lesson List */

.lesson-list {
    margin: 25px 0 80px;
}

.lesson-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px;
    border-bottom: 1px solid #244565;
    text-decoration: none;
    color: #edf4fc;
}

.lesson-item:hover {
    color: #61c4ed;
    background: #102b4b;
}

.back-link {
    display: inline-block;
    color: #61c4ed;
    text-decoration: none;
    margin-top: 30px;
    font-size: 14px;
}

/* Article / Lesson Pages */

.article-container {
    max-width: 850px;
}

.article {
    padding: 40px 0 80px;
}

.article h1 {
    font-size: 38px;
    margin-bottom: 15px;
}

.article h2 {
    margin-top: 35px;
    margin-bottom: 15px;
}

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

.article p {
    color: #d0ddec;
    margin-bottom: 18px;
}

.article ul,
.article ol {
    margin: 15px 0 20px 25px;
    color: #d0ddec;
}

.article li {
    margin-bottom: 8px;
}

.article pre {
    background: #031020;
    padding: 22px;
    border-radius: 8px;
    overflow-x: auto;
    margin: 20px 0;
    border: 1px solid #244565;
}

.article pre code {
    color: #a9e1fa;
    font-family: Consolas, monospace;
    font-size: 14px;
}

.article code:not(pre code) {
    background: #193858;
    color: #8ddafa;
    padding: 2px 5px;
    border-radius: 3px;
}

/* Footer */

footer {
    text-align: center;
    padding: 30px;
    border-top: 1px solid #203b5c;
    color: #8fa6bf;
    font-size: 13px;
}

/* Responsive Layout */

@media (max-width: 768px) {
    .container {
        width: 90%;
    }

    .course-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .hero h1 {
        font-size: 32px;
    }
}

@media (max-width: 500px) {
    header {
        padding: 18px 5%;
    }

    .logo {
        font-size: 15px;
    }

    nav a {
        margin-left: 10px;
    }

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

    .category-title {
        font-size: 19px;
    }

    .course-card {
        padding: 20px;
    }

    .article h1 {
        font-size: 30px;
    }
}