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

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    line-height: 1.6;
    color: #2c3e50;
    background: #ffffff;
}

header {
    padding: 3rem 2rem;
    max-width: 900px;
    margin: 0 auto;
    border-bottom: 1px solid #ecf0f1;
    position: relative;
}

.language-selector {
    position: absolute;
    top: 2rem;
    right: 2rem;
    font-size: 0.85rem;
    color: #7f8c8d;
}

.language-selector a {
    color: #7f8c8d;
    text-decoration: none;
    transition: color 0.2s;
    width: 2rem;
    display: inline-block;
    text-align: center;
}

.language-selector a:hover {
    color: #1a5490;
}

.language-selector .current {
    color: #2c3e50;
    font-weight: 500;
    pointer-events: none;
    width: 2rem;
    display: inline-block;
    text-align: center;
}

.header-identity {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

.logo-image {
    width: 60px;
    height: 60px;
    object-fit: contain;
    flex-shrink: 0;
}

.logo-text {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.logo {
    font-size: 1.5rem;
    font-weight: 600;
    letter-spacing: -0.5px;
    color: #1a5490;
    margin: 0;
}

.tagline {
    font-size: 0.95rem;
    color: #7f8c8d;
    font-weight: 500;
    margin: 0;
}

.header-description {
    font-size: 1rem;
    color: #555;
    line-height: 1.7;
    margin-top: 1rem;
}

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

section {
    padding: 3rem 0;
    border-bottom: 1px solid #ecf0f1;
}

section:last-child {
    border-bottom: none;
}

h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: #1a5490;
}

h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    color: #2c3e50;
}

p {
    font-size: 0.95rem;
    color: #555;
    margin-bottom: 1rem;
    line-height: 1.8;
}

ul, ol {
    margin-left: 1.5rem;
    margin-bottom: 1rem;
}

li {
    margin-bottom: 0.5rem;
    color: #555;
    font-size: 0.95rem;
}

.grid-2 {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin: 1.5rem 0;
}

.diagram-box {
    background: #f8f9fa;
    border: 1px solid #e0e6ed;
    border-radius: 4px;
    padding: 2rem;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 250px;
}

.diagram-label {
    font-size: 0.9rem;
    color: #7f8c8d;
    text-align: center;
    margin-top: 1rem;
}

svg {
    width: 100%;
    height: auto;
}

.callout-box {
    background: #f0f4f8;
    border-left: 4px solid #1a5490;
    padding: 1.5rem;
    margin: 1.5rem 0;
    border-radius: 2px;
}

.callout-box p {
    margin: 0;
    font-size: 0.95rem;
    color: #2c3e50;
}

.what-not {
    background: #fef5f1;
    border-left: 4px solid #e67e22;
    padding: 1.5rem;
    margin: 1.5rem 0;
    border-radius: 2px;
}

.what-not h4 {
    font-weight: 600;
    color: #d35400;
    margin-bottom: 0.75rem;
    font-size: 0.95rem;
}

.what-not p {
    margin: 0.5rem 0;
}

.tag-structure {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
    margin: 1.5rem 0;
}

.tag-type {
    background: #f8f9fa;
    border: 1px solid #e0e6ed;
    padding: 1.5rem;
    border-radius: 4px;
}

.tag-type h4 {
    font-weight: 600;
    color: #1a5490;
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.tag-type p {
    font-size: 0.9rem;
    color: #7f8c8d;
    margin: 0;
}

.use-case-list {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin: 1.5rem 0;
}

.use-case-item {
    display: flex;
    gap: 1rem;
    align-items: flex-start;
}

.use-case-icon {
    font-size: 1.2rem;
    color: #1a5490;
    font-weight: bold;
    flex-shrink: 0;
    margin-top: 0.1rem;
}

.use-case-text {
    font-size: 0.95rem;
    color: #555;
    line-height: 1.6;
}

footer {
    background: #f8f9fa;
    padding: 2rem;
    text-align: center;
    color: #7f8c8d;
    font-size: 0.9rem;
    margin-top: 2rem;
}

footer p {
    margin: 0.5rem 0;
    font-size: 0.9rem;
}

footer a {
    color: #1a5490;
    text-decoration: none;
}

footer a:hover {
    text-decoration: underline;
}

@media (max-width: 768px) {
    .grid-2, .tag-structure, .use-case-list {
        grid-template-columns: 1fr;
    }

    .header-identity {
        flex-direction: row;
        gap: 1rem;
        align-items: center;
    }

    .logo-image {
        width: 50px;
        height: 50px;
    }

    .logo {
        font-size: 1.2rem;
    }

    .tagline {
        font-size: 0.9rem;
    }

    .language-selector {
        position: static;
        margin-bottom: 1rem;
        font-size: 0.8rem;
    }

    header {
        padding: 2rem 1.5rem;
    }

    h2 {
        font-size: 1.3rem;
    }

    header {
        padding: 2rem 1.5rem;
    }

    main {
        padding: 0 1.5rem;
    }

    section {
        padding: 2rem 0;
    }
}