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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: #333;
    background: #fff;
}

header {
    background: #000;
    color: #fff;
    padding: 2rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

header h1 {
    text-align: center;
    font-size: 2rem;
    font-weight: 300;
    margin-bottom: 1rem;
    letter-spacing: -0.02em;
}

nav ul {
    display: flex;
    justify-content: center;
    gap: 2rem;
    list-style: none;
    flex-wrap: wrap;
}

nav a {
    color: #fff;
    text-decoration: none;
    font-weight: 400;
    padding: 0.5rem 1rem;
    border: 1px solid #333;
    transition: all 0.2s ease;
}

nav a:hover {
    background: #fff;
    color: #000;
}

main {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 2rem;
}

section {
    margin: 4rem 0;
    padding: 2rem 0;
}

section:not(:last-child) {
    border-bottom: 1px solid #eee;
}

h2 {
    font-size: 2rem;
    font-weight: 300;
    margin-bottom: 1rem;
}

h3 {
    font-size: 1.5rem;
    font-weight: 400;
    margin-bottom: 1.5rem;
    text-align: center;
}

h4 {
    font-size: 1.2rem;
    font-weight: 500;
    margin-bottom: 1rem;
}

p {
    margin-bottom: 1rem;
    color: #666;
}

#hero {
    text-align: center;
    padding: 4rem 0;
}

#hero button {
    background: #000;
    color: #fff;
    border: none;
    padding: 1rem 2rem;
    font-size: 1rem;
    cursor: pointer;
    margin-top: 2rem;
    transition: background 0.2s ease;
}

#hero button:hover {
    background: #333;
}

#background ul,
#effects > div,
#limitations ol {
    list-style: none;
}

#background li {
    margin: 0.5rem 0;
    padding-left: 1rem;
    position: relative;
}

#background li::before {
    content: '•';
    position: absolute;
    left: 0;
}

#effects > div {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

#effects > div > div {
    padding: 2rem;
    border: 1px solid #eee;
    transition: border-color 0.2s ease;
}

#effects > div > div:hover {
    border-color: #000;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin: 2rem 0;
}

th, td {
    text-align: left;
    padding: 1rem;
    border-bottom: 1px solid #eee;
}

th {
    background: #f8f8f8;
    font-weight: 500;
}

blockquote {
    border-left: 4px solid #000;
    padding-left: 2rem;
    margin: 2rem 0;
    font-style: italic;
    color: #666;
}

#limitations ol {
    counter-reset: item;
}

#limitations li {
    counter-increment: item;
    margin: 1.5rem 0;
    padding-left: 2rem;
    position: relative;
}

#limitations li::before {
    content: counter(item);
    position: absolute;
    left: 0;
    top: 0;
    background: #000;
    color: #fff;
    width: 1.5rem;
    height: 1.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.8rem;
    font-weight: 500;
}

#limitations strong {
    display: block;
    margin-bottom: 0.5rem;
    color: #000;
}

aside {
    background: #f8f8f8;
    padding: 2rem;
    margin: 2rem 0;
}

fieldset {
    border: 1px solid #ddd;
    padding: 1.5rem;
    margin-top: 1rem;
}

legend {
    font-weight: 500;
    padding: 0 0.5rem;
}

label {
    display: block;
    margin: 1rem 0 0.25rem 0;
    font-weight: 500;
}

input[type="text"],
textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #ddd;
    font-size: 1rem;
    font-family: inherit;
}

input[type="text"]:focus,
textarea:focus {
    outline: none;
    border-color: #000;
}

input[type="submit"] {
    background: #000;
    color: #fff;
    border: none;
    padding: 0.75rem 1.5rem;
    cursor: pointer;
    margin-top: 1rem;
    transition: background 0.2s ease;
}

input[type="submit"]:hover {
    background: #333;
}

footer {
    background: #000;
    color: #fff;
    text-align: center;
    padding: 2rem;
    margin-top: 4rem;
}

footer p {
    color: #ccc;
    margin-bottom: 0.5rem;
}

footer a {
    color: #fff;
}

/* 다크 테마용 한계 섹션 넘버링 */
#limitations.dark-theme li::before {
    background: #fff;
    color: #000;
}

@media (max-width: 768px) {
    main {
        padding: 0 1rem;
    }
    
    nav ul {
        flex-direction: column;
        gap: 0.5rem;
    }
    
    #effects > div {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    th, td {
        padding: 0.5rem;
        font-size: 0.9rem;
    }
}