.concept-page {
    background: radial-gradient(circle at 15% -10%, rgba(99, 102, 241, 0.18), transparent 45%), var(--color-bg);
    font-family: "Noto Serif KR", "Noto Serif", serif;
}

[data-theme="light"] .concept-page {
    background: radial-gradient(circle at 15% -10%, rgba(168, 152, 80, 0.22), transparent 50%), var(--color-bg);
}

.concept-page main {
    max-width: 960px;
    margin: 0 auto;
}

.concept-page .eyebrow,
.concept-page .h1,
.concept-page .section-title,
.concept-page .chip,
.concept-page .btn,
.concept-page .concept-toc {
    font-family: "Noto Sans KR", "Noto Sans", sans-serif;
}

.concept-page .tools-section {
    padding: 0;
    margin: var(--space-7) 0;
    background: transparent;
    border: none;
    box-shadow: none;
}

.concept-page .section-heading {
    margin-bottom: var(--space-3);
}

.concept-page .section-title {
    position: relative;
    padding-bottom: var(--space-2);
}

.concept-page .section-title::after {
    content: "";
    display: block;
    width: 48px;
    height: 3px;
    margin-top: var(--space-2);
    border-radius: 999px;
    background: linear-gradient(90deg, var(--color-accent), rgba(56, 189, 248, 0.6));
}

.concept-hero .hero-inner {
    align-items: stretch;
    gap: var(--space-6);
}

.concept-hero .hero-copy {
    max-width: 640px;
}

.concept-hero .hero-description {
    font-size: var(--font-md);
    line-height: 1.7;
}

.concept-hero .hero-panel {
    background: rgba(15, 23, 42, 0.45);
    border: 1px solid rgba(148, 163, 184, 0.2);
}

[data-theme="light"] .concept-hero .hero-panel {
    background: rgba(255, 255, 255, 0.7);
    border-color: rgba(148, 163, 184, 0.35);
}

.concept-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
    margin: var(--space-3) 0 0;
}

.concept-meta .chip {
    border-color: var(--color-border);
}

.concept-toc {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-lg);
    border: 1px dashed rgba(148, 163, 184, 0.35);
    background: rgba(15, 23, 42, 0.35);
}

[data-theme="light"] .concept-toc {
    background: rgba(255, 255, 255, 0.7);
    border-color: rgba(148, 163, 184, 0.45);
}

.concept-toc-title {
    font-weight: 600;
    color: var(--color-text);
    margin-right: var(--space-2);
}

.concept-toc-links {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2);
}

.concept-toc-links a {
    text-decoration: none;
    color: var(--color-text-soft);
    border: 1px solid rgba(148, 163, 184, 0.25);
    border-radius: 999px;
    padding: 4px 12px;
    font-size: var(--font-sm);
    transition: border-color var(--transition), color var(--transition), background var(--transition);
}

.concept-toc-links a:hover {
    color: var(--color-text);
    border-color: var(--color-accent);
    background: var(--color-accent-soft);
}

.concept-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: var(--space-3);
}

.concept-grid .card {
    border-top: 2px solid rgba(99, 102, 241, 0.35);
}

.concept-article {
    display: grid;
    gap: var(--space-3);
    color: var(--color-text);
    line-height: 1.7;
    font-size: var(--font-md);
    padding: var(--space-5);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    background: var(--color-surface);
    box-shadow: var(--shadow-sm);
    position: relative;
}

.concept-article p {
    font-size: clamp(0.95rem, 0.75vw + 0.9rem, 1.05rem);
}

.concept-article p {
    margin: 0;
    padding-left: calc(var(--space-4) + 6px);
}

.concept-article::before {
    content: "";
    position: absolute;
    inset: var(--space-4) auto var(--space-4) var(--space-4);
    width: 3px;
    border-radius: 999px;
    background: linear-gradient(180deg, rgba(59, 130, 246, 0.9), rgba(14, 116, 144, 0.6));
}

.concept-glossary {
    display: grid;
    gap: var(--space-3);
    margin: 0;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}

.concept-glossary .card {
    display: grid;
    gap: var(--space-2);
}

.concept-glossary dt {
    font-weight: 600;
    font-size: var(--font-lg);
}

.concept-glossary dd {
    margin: 0;
    color: var(--color-text-soft);
}

.concept-steps {
    display: grid;
    gap: var(--space-3);
    margin: 0;
    padding: 0;
    list-style: none;
    counter-reset: concept-step;
}

.concept-steps li {
    display: grid;
    gap: var(--space-2);
    padding: var(--space-4);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    background: var(--color-surface);
    box-shadow: var(--shadow-sm);
    position: relative;
    padding-left: calc(var(--space-6) + 8px);
}

.concept-steps li::before {
    counter-increment: concept-step;
    content: counter(concept-step);
    position: absolute;
    left: var(--space-4);
    top: var(--space-4);
    width: 32px;
    height: 32px;
    border-radius: 50%;
    display: grid;
    place-items: center;
    font-weight: 700;
    color: #fff;
    background: linear-gradient(135deg, rgba(79, 70, 229, 0.9), rgba(56, 189, 248, 0.85));
    box-shadow: 0 8px 16px rgba(37, 99, 235, 0.25);
}

.concept-steps li strong {
    font-size: var(--font-lg);
}

.concept-steps li span {
    color: var(--color-text-soft);
}

.concept-example-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: var(--space-3);
    align-items: stretch;
}

.concept-example pre {
    margin: var(--space-3) 0 0;
    padding: var(--space-3);
    border-radius: var(--radius-md);
    background: rgba(15, 23, 42, 0.35);
    border: 1px solid rgba(148, 163, 184, 0.2);
    overflow: auto;
    font-family: "JetBrains Mono", "Fira Code", "SFMono-Regular", ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas,
        "Liberation Mono", "Courier New", monospace;
    font-size: var(--font-sm);
    color: #e2e8f0;
}

.concept-example pre code {
    display: block;
    line-height: 1.6;
    white-space: pre-wrap;
}

[data-theme="light"] .concept-example pre {
    background: rgba(226, 232, 240, 0.6);
    border-color: rgba(148, 163, 184, 0.35);
    color: #0f172a;
}

.concept-callout {
    display: flex;
    gap: var(--space-3);
    align-items: flex-start;
    padding: var(--space-4);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(56, 189, 248, 0.35);
    background: rgba(56, 189, 248, 0.08);
    margin-bottom: var(--space-3);
}

.concept-callout .material-symbols-rounded {
    font-size: 24px;
    color: #38bdf8;
}

[data-theme="light"] .concept-callout {
    background: rgba(14, 116, 144, 0.08);
    border-color: rgba(14, 116, 144, 0.25);
}

[data-theme="light"] .concept-callout .material-symbols-rounded {
    color: #0e7490;
}

.concept-list {
    margin: 0;
    padding-left: var(--space-4);
    display: grid;
    gap: var(--space-2);
    color: var(--color-text-soft);
}

.concept-list ::marker {
    color: var(--color-accent);
}

.concept-faq {
    display: grid;
    gap: var(--space-3);
}

.concept-faq details {
    padding: var(--space-3);
    cursor: pointer;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    background: var(--color-surface);
    box-shadow: var(--shadow-sm);
    transition: border-color var(--transition), background var(--transition);
}

.concept-faq summary {
    font-weight: 600;
    list-style: none;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-2);
}

.concept-faq summary::-webkit-details-marker {
    display: none;
}

.concept-faq summary::after {
    content: "expand_more";
    font-family: "Material Symbols Rounded";
    font-size: 20px;
    color: var(--color-text-soft);
}

.concept-faq details[open] {
    border-color: rgba(99, 102, 241, 0.4);
    background: rgba(99, 102, 241, 0.06);
}

.concept-faq details[open] summary::after {
    content: "expand_less";
}

.concept-faq p {
    margin: var(--space-2) 0 0;
    color: var(--color-text-soft);
}

.concept-link {
    color: inherit;
    text-decoration: none;
    display: grid;
    gap: var(--space-2);
}

.concept-link:hover {
    border-color: var(--color-accent);
}

.concept-link:focus-visible {
    outline: 2px solid var(--color-focus);
    outline-offset: 2px;
}

@media (max-width: 768px) {
    .concept-page main {
        max-width: 100%;
    }

    .concept-toc {
        padding: var(--space-3);
    }

    .concept-article {
        padding: var(--space-4);
    }

    .concept-article::before {
        inset: var(--space-3) auto var(--space-3) var(--space-3);
    }

    .concept-article p {
        padding-left: calc(var(--space-3) + 6px);
    }

    .concept-steps li {
        padding: var(--space-3);
        padding-left: calc(var(--space-5) + 6px);
    }

    .concept-steps li::before {
        left: var(--space-3);
        top: var(--space-3);
        width: 28px;
        height: 28px;
    }
}