body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    transition: background-color 220ms ease;
}

body:hover {
    background-color: #f8fbff;
}

header {
    background-color: #1E3A8A;
    color: white;
    padding: 10px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header .logo {
    height: 50px;
}

nav ul {
    list-style: none;
    display: flex;
    gap: 15px;
    margin: 0;
    padding: 0;
}

nav ul li a {
    color: white;
    text-decoration: none;
    transition: color 160ms ease, transform 160ms ease;
}

nav ul li a:hover,
nav ul li a:focus {
    color: #e2e8f0;
    transform: translateY(-1px);
}

nav ul li a.active {
    text-decoration: underline;
}

.hero {
    text-align: center;
    padding: 100px 20px;
    background-color: #f0f4f8;
}

.hero h1 {
    font-size: 48px;
    margin-bottom: 20px;
}

.hero .btn {
    background-color: #1E3A8A;
    color: white;
    padding: 10px 20px;
    text-decoration: none;
    border-radius: 5px;
    transition: background-color 160ms ease, transform 160ms ease;
}

.hero .btn:hover,
.hero .btn:focus {
    background-color: #16357f;
    transform: translateY(-1px);
}

.features {
    padding: 50px 20px;
    text-align: center;
}

.features ul {
    list-style: none;
    padding: 0;
}

.features ul li {
    margin: 10px 0;
}

.content {
    padding: 50px 20px;
}

.courses {
    padding: 50px 20px;
    max-width: 1100px;
    margin: 0 auto;
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.course-card {
    border: 1px solid rgba(0, 0, 0, 0.12);
    border-radius: 10px;
    padding: 20px;
    background: white;
    box-shadow: 0 5px 18px rgba(0, 0, 0, 0.05);
    display: flex;
    flex-direction: column;
    gap: 12px;
    transition: box-shadow 150ms ease, transform 150ms ease;
}

.course-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 16px 28px rgba(0, 0, 0, 0.12);
}

.course-card h3 {
    margin: 0;
    font-size: 1.25rem;
}

.course-card p {
    margin: 0;
    color: #333;
    line-height: 1.4;
}

.course-card .meta {
    display: flex;
    justify-content: space-between;
    font-size: 0.9rem;
    color: #555;
}

.course-card a {
    margin-top: auto;
    align-self: flex-start;
    background-color: #1E3A8A;
    color: white;
    padding: 10px 14px;
    border-radius: 6px;
    text-decoration: none;
}

.course-card a:hover {
    background-color: #16357f;
}

.video-container {
    max-width: 900px;
    margin: 0 auto;
    aspect-ratio: 16 / 9;
    background: #000;
    overflow: hidden;
    border-radius: 12px;
}

.video-container iframe {
    width: 100%;
    height: 100%;
}

.caption {
    max-width: 900px;
    margin: 14px auto 0;
    font-size: 0.95rem;
    color: #555;
    text-align: center;
}

footer {
    background-color: #1E3A8A;
    color: white;
    text-align: center;
    padding: 20px;
}

@media (max-width: 720px) {
    header {
        flex-wrap: wrap;
        padding: 12px;
    }

    nav ul {
        flex-direction: column;
        width: 100%;
        gap: 10px;
        padding: 10px 0;
    }

    nav ul li {
        width: 100%;
        text-align: center;
    }

    nav ul li a {
        display: block;
        padding: 10px 0;
    }

    .hero {
        padding: 70px 16px;
    }

    .hero h1 {
        font-size: 36px;
    }

    .features,
    .courses,
    .content {
        padding: 30px 16px;
    }

    .course-card .meta {
        flex-direction: column;
        gap: 8px;
    }

    .caption {
        padding: 0 16px;
    }
}