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

body {
    font-family: Arial, Helvetica, sans-serif;
    background-color: #eef2f5;
    color: #1f2933;
    line-height: 1.7;
    padding: 30px;
}


main, header, article {
    background-color: #ffffff;
    max-width: 900px;
    margin: 0 auto 30px auto;
    padding: 25px;
    border-radius: 14px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.08);
}


h1 {
    text-align: center;
    color: #0f172a;
    margin-bottom: 15px;
}

h2 {
    color: #1e3a8a;
    margin-bottom: 10px;
}

h3 {
    color: #1e40af;
    margin: 20px 0 10px;
}

h4 {
    color: #334155;
    margin-top: 15px;
}


img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 20px auto;
    border-radius: 12px;
}


p {
    margin-bottom: 15px;
}


a {
    color: #2563eb;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}


nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-top: 15px;
}

nav li a {
    font-weight: bold;
    color: #1e40af;
}


ol {
    margin: 15px 0 20px 20px;
}

ol li {
    margin-bottom: 8px;
    font-size: 17px;
}


ul {
    margin-left: 20px;
    margin-bottom: 20px;
}

ul li {
    margin-bottom: 6px;
}

section {
    margin-top: 25px;
    padding-top: 10px;
    border-top: 1px solid #e5e7eb;
}

footer {
    text-align: center;
    color: #475569;
    font-size: 14px;
    margin-top: 30px;
}