:root {
    --ink: #172033;
    --muted: #667085;
    --subtle: #8a94a6;
    --line: #e3e8f0;
    --surface: #ffffff;
    --surface-soft: #f6f8fb;
    --surface-blue: #eef4ff;
    --brand: #3157d5;
    --brand-dark: #2442aa;
    --accent: #e8505b;
    --code: #111827;
    --shadow: 0 16px 45px rgba(23, 32, 51, 0.08);
    --radius-large: 24px;
    --radius-medium: 16px;
    --shell: 1180px;
    font-family: Inter, Pretendard, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    color: var(--ink);
    background: var(--surface-soft);
    font-synthesis: none;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    min-width: 320px;
    margin: 0;
    background: var(--surface-soft);
    color: var(--ink);
    line-height: 1.6;
}

a {
    color: inherit;
}

button,
input,
select {
    font: inherit;
}

button,
select {
    cursor: pointer;
}

[hidden] {
    display: none !important;
}

.shell {
    width: min(calc(100% - 40px), var(--shell));
    margin-inline: auto;
}

.skip-link {
    position: fixed;
    z-index: 100;
    top: 12px;
    left: 12px;
    padding: 10px 14px;
    transform: translateY(-160%);
    border-radius: 10px;
    background: var(--ink);
    color: white;
}

.skip-link:focus {
    transform: translateY(0);
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.site-header {
    position: relative;
    z-index: 10;
    border-bottom: 1px solid rgba(227, 232, 240, 0.85);
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(12px);
}

.header-inner {
    min-height: 72px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.brand,
.header-link,
.header-nav-link {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    font-weight: 750;
}

.brand-mark {
    display: grid;
    width: 38px;
    height: 38px;
    place-items: center;
    border-radius: 12px;
    background: var(--ink);
    color: white;
    font-family: "SFMono-Regular", Consolas, monospace;
    font-size: 13px;
}

.header-nav {
    display: flex;
    align-items: center;
    gap: 6px;
}

.header-link,
.header-nav-link {
    position: relative;
    min-height: 40px;
    padding: 0 12px;
    border-radius: 10px;
    color: var(--muted);
    font-size: 14px;
}

.header-link:hover,
.header-link:focus-visible,
.header-nav-link:hover,
.header-nav-link:focus-visible,
.header-nav-link.is-active {
    background: var(--surface-blue);
    color: var(--brand);
}

.notice-nav-link {
    padding-right: 16px;
}

.notice-indicator {
    position: absolute;
    top: 2px;
    right: 1px;
    display: inline-flex;
    min-width: 18px;
    height: 18px;
    align-items: center;
    justify-content: center;
    padding-inline: 4px;
    border: 2px solid var(--surface);
    border-radius: 999px;
    background: var(--accent);
    color: white;
    font-size: 9px;
    font-weight: 900;
    line-height: 1;
}

.hero {
    position: relative;
    overflow: hidden;
    border-bottom: 1px solid var(--line);
    background:
        radial-gradient(circle at 82% 24%, rgba(49, 87, 213, 0.16), transparent 28%),
        linear-gradient(135deg, #ffffff 0%, #f4f7ff 56%, #eef2ff 100%);
}

.hero::after {
    content: "";
    position: absolute;
    width: 320px;
    height: 320px;
    right: max(calc((100vw - var(--shell)) / 2), 20px);
    bottom: -220px;
    border: 52px solid rgba(232, 80, 91, 0.07);
    border-radius: 50%;
}

.hero-inner {
    position: relative;
    z-index: 1;
    padding-block: 84px 76px;
}

.eyebrow {
    margin: 0 0 12px;
    color: var(--brand);
    font-size: 12px;
    font-weight: 850;
    letter-spacing: 0.16em;
}

.hero h1 {
    max-width: 760px;
    margin: 0;
    font-size: clamp(42px, 7vw, 76px);
    line-height: 1.08;
    letter-spacing: -0.055em;
}

.hero h1 span {
    color: var(--brand);
}

.hero-copy {
    max-width: 620px;
    margin: 26px 0 0;
    color: var(--muted);
    font-size: 18px;
}

.stats {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin: 42px 0 0;
}

.stats div {
    min-width: 132px;
    padding: 15px 20px;
    border: 1px solid rgba(49, 87, 213, 0.12);
    border-radius: 14px;
    background: rgba(255, 255, 255, 0.75);
}

.stats dt {
    color: var(--muted);
    font-size: 12px;
    font-weight: 700;
}

.stats dd {
    margin: 1px 0 0;
    font-size: 24px;
    font-weight: 850;
    letter-spacing: -0.03em;
}

.catalog-section {
    padding-block: 72px 92px;
}

.section-heading {
    display: flex;
    align-items: end;
    justify-content: space-between;
    gap: 20px;
    margin-bottom: 24px;
}

.section-heading h2,
.description-card h2 {
    margin: 0;
    font-size: 30px;
    letter-spacing: -0.035em;
}

.result-count {
    margin: 0;
    color: var(--muted);
    font-weight: 700;
}

.filters {
    display: grid;
    grid-template-columns: minmax(260px, 1.8fr) repeat(2, minmax(140px, 0.8fr)) auto;
    gap: 10px;
    margin-bottom: 28px;
}

.filters input,
.filters select {
    width: 100%;
    height: 50px;
    border: 1px solid var(--line);
    border-radius: 12px;
    outline: none;
    background: var(--surface);
    color: var(--ink);
}

.filters input {
    padding: 0 16px 0 44px;
}

.filters select {
    padding: 0 34px 0 14px;
}

.filters input:focus,
.filters select:focus {
    border-color: var(--brand);
    box-shadow: 0 0 0 3px rgba(49, 87, 213, 0.12);
}

.search-field {
    position: relative;
}

.search-icon {
    position: absolute;
    z-index: 1;
    top: 50%;
    left: 16px;
    transform: translateY(-52%);
    color: var(--subtle);
    font-size: 24px;
}

.button {
    display: inline-flex;
    min-height: 48px;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 0 18px;
    border: 1px solid transparent;
    border-radius: 12px;
    text-decoration: none;
    font-weight: 800;
}

.button-primary {
    background: var(--brand);
    color: white;
    box-shadow: 0 8px 22px rgba(49, 87, 213, 0.2);
}

.button-primary:hover,
.button-primary:focus-visible {
    background: var(--brand-dark);
}

.button-muted {
    border-color: var(--line);
    background: var(--surface);
    color: var(--muted);
}

.button-muted:hover,
.button-muted:focus-visible {
    border-color: #c4ccda;
    color: var(--ink);
}

.problem-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 16px;
}

.problem-card {
    display: flex;
    min-height: 230px;
    flex-direction: column;
    padding: 24px;
    border: 1px solid var(--line);
    border-radius: var(--radius-medium);
    background: var(--surface);
    transition: transform 160ms ease, box-shadow 160ms ease, border-color 160ms ease;
}

.problem-card:hover {
    transform: translateY(-3px);
    border-color: #cad3e3;
    box-shadow: var(--shadow);
}

.card-topline {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
}

.platform-badge {
    display: inline-flex;
    align-items: center;
    min-height: 28px;
    padding: 4px 10px;
    border-radius: 999px;
    background: var(--surface-blue);
    color: var(--brand-dark);
    font-size: 12px;
    font-weight: 850;
}

.platform-leetcode {
    background: #fff5df;
    color: #8a5b00;
}

.platform-programmers {
    background: #eaf8f2;
    color: #17694d;
}

.platform-hackerrank {
    background: #e8f8ec;
    color: #18622b;
}

.problem-number {
    color: var(--subtle);
    font-family: "SFMono-Regular", Consolas, monospace;
    font-size: 13px;
    font-weight: 700;
}

.problem-card h3 {
    margin: 20px 0 16px;
    font-size: 20px;
    line-height: 1.35;
    letter-spacing: -0.025em;
}

.problem-card h3 a {
    text-decoration: none;
}

.problem-card h3 a::after {
    content: "";
    position: absolute;
    inset: 0;
}

.problem-card {
    position: relative;
}

.language-list {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.language-list span {
    padding: 3px 8px;
    border-radius: 7px;
    background: var(--surface-soft);
    color: var(--muted);
    font-size: 12px;
    font-weight: 750;
}

.card-footer {
    position: relative;
    z-index: 1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-top: auto;
    padding-top: 20px;
    color: var(--muted);
    font-size: 13px;
}

.card-footer a {
    color: var(--brand);
    text-decoration: none;
    font-weight: 800;
}

.empty-state {
    padding: 70px 20px;
    border: 1px dashed #cbd3df;
    border-radius: var(--radius-large);
    text-align: center;
    color: var(--muted);
}

.empty-state p {
    margin: 0 0 18px;
    font-size: 18px;
}

.pagination {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: 7px;
    margin-top: 34px;
}

.pagination-button {
    min-width: 42px;
    height: 42px;
    padding: 0 12px;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: var(--surface);
    color: var(--muted);
    font-weight: 800;
}

.pagination-button:hover:not(:disabled),
.pagination-button:focus-visible,
.pagination-button.is-current {
    border-color: var(--brand);
    color: var(--brand);
}

.pagination-button.is-current {
    background: var(--surface-blue);
}

.pagination-button:disabled {
    cursor: not-allowed;
    opacity: 0.42;
}

.pagination-ellipsis {
    padding-inline: 2px;
    color: var(--subtle);
}

.announcement-page {
    min-height: calc(100vh - 173px);
    padding-block: 64px 92px;
}

.announcement-hero {
    margin-bottom: 34px;
}

.announcement-hero h1 {
    margin: 0;
    font-size: clamp(38px, 6vw, 58px);
    letter-spacing: -0.05em;
}

.announcement-hero > p:last-child {
    margin: 12px 0 0;
    color: var(--muted);
    font-size: 17px;
}

.announcement-list {
    display: grid;
    gap: 18px;
}

.announcement-card {
    scroll-margin-top: 24px;
    overflow: hidden;
    border: 1px solid var(--line);
    border-radius: var(--radius-medium);
    background: var(--surface);
    box-shadow: 0 8px 28px rgba(23, 32, 51, 0.04);
}

.announcement-summary {
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: center;
    gap: 24px;
    padding: 24px 28px;
    background: linear-gradient(120deg, #fff, #f7f9ff);
    cursor: pointer;
    list-style: none;
    transition: background 160ms ease;
}

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

.announcement-summary:hover,
.announcement-card[open] > .announcement-summary {
    background: linear-gradient(120deg, #f9fbff, #f1f5ff);
}

.announcement-summary:focus-visible {
    outline: 3px solid rgba(47, 91, 234, 0.26);
    outline-offset: -3px;
}

.announcement-summary-main {
    display: flex;
    min-width: 0;
    align-items: center;
    gap: 10px;
}

.announcement-title {
    font-size: 22px;
    font-weight: 850;
    line-height: 1.35;
    letter-spacing: -0.025em;
}

.announcement-meta {
    display: flex;
    align-items: center;
    gap: 16px;
}

.announcement-meta time {
    color: var(--muted);
    font-size: 13px;
    font-weight: 700;
}

.announcement-chevron {
    width: 10px;
    height: 10px;
    border-right: 2px solid var(--subtle);
    border-bottom: 2px solid var(--subtle);
    transform: rotate(45deg) translate(-2px, -2px);
    transition: transform 160ms ease;
}

.announcement-card[open] .announcement-chevron {
    transform: rotate(225deg) translate(-2px, -2px);
}

.new-badge {
    display: inline-flex;
    min-height: 24px;
    align-items: center;
    padding: 2px 8px;
    border-radius: 999px;
    background: #fff0f1;
    color: var(--accent);
    font-size: 10px;
    font-weight: 900;
    letter-spacing: 0.05em;
}

.announcement-body {
    padding: 26px 28px 30px;
    border-top: 1px solid var(--line);
    color: #39445a;
}

.announcement-body > :first-child {
    margin-top: 0;
}

.announcement-body > :last-child {
    margin-bottom: 0;
}

.announcement-body a {
    color: var(--brand);
    font-weight: 750;
}

.announcement-body code {
    padding: 2px 6px;
    border-radius: 6px;
    background: var(--surface-soft);
    font-family: "SFMono-Regular", Consolas, monospace;
    font-size: 0.9em;
}

.announcement-body pre {
    padding: 18px;
    overflow-x: auto;
    border-radius: 12px;
    background: var(--code);
    color: #d9e1ec;
}

.announcement-body pre code {
    padding: 0;
    background: transparent;
}

.announcement-body blockquote {
    margin-inline: 0;
    padding-left: 18px;
    border-left: 4px solid var(--brand);
    color: var(--muted);
}

.announcement-empty {
    background: var(--surface);
}

.announcement-empty p {
    margin-bottom: 0;
}

.problem-page {
    padding-block: 34px 92px;
}

.breadcrumbs {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 28px;
    color: var(--muted);
    font-size: 14px;
}

.breadcrumbs a {
    text-decoration: none;
}

.breadcrumbs a:hover {
    color: var(--brand);
}

.problem-hero {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 30px;
    padding: 36px;
    border: 1px solid var(--line);
    border-radius: var(--radius-large);
    background:
        linear-gradient(115deg, rgba(255, 255, 255, 0.95), rgba(238, 244, 255, 0.9)),
        var(--surface);
    box-shadow: 0 10px 34px rgba(23, 32, 51, 0.05);
}

.problem-hero .card-topline {
    justify-content: flex-start;
}

.problem-hero h1 {
    margin: 14px 0 5px;
    font-size: clamp(30px, 5vw, 48px);
    line-height: 1.16;
    letter-spacing: -0.045em;
}

.problem-hero p {
    margin: 0;
    color: var(--muted);
}

.solution-tabs {
    display: flex;
    gap: 8px;
    margin: 28px 0 16px;
    padding: 6px;
    overflow-x: auto;
    border: 1px solid var(--line);
    border-radius: 14px;
    background: var(--surface);
}

.solution-tabs button {
    display: flex;
    min-width: max-content;
    flex-direction: column;
    align-items: flex-start;
    padding: 9px 16px;
    border: 0;
    border-radius: 9px;
    background: transparent;
    color: var(--muted);
}

.solution-tabs button[aria-selected="true"] {
    background: var(--ink);
    color: white;
}

.solution-tabs strong {
    font-size: 13px;
}

.solution-tabs span {
    font-size: 11px;
    opacity: 0.75;
}

.solution-stack {
    margin-top: 28px;
}

.solution-panel {
    display: grid;
    gap: 22px;
}

.solution-info,
.description-card {
    padding: 28px;
    border: 1px solid var(--line);
    border-radius: var(--radius-medium);
    background: var(--surface);
}

.solution-info {
    display: grid;
    grid-template-columns: minmax(220px, 0.7fr) minmax(0, 1.3fr);
    gap: 30px;
}

.solution-info h2 {
    margin: 0;
    font-size: 24px;
    letter-spacing: -0.03em;
}

.metadata-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 18px;
    margin: 0;
}

.metadata-grid div {
    min-width: 0;
}

.metadata-grid dt {
    color: var(--subtle);
    font-size: 12px;
    font-weight: 750;
}

.metadata-grid dd {
    margin: 4px 0 0;
    overflow-wrap: anywhere;
    font-size: 14px;
    font-weight: 700;
}

.metadata-links {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 3px;
}

.metadata-links a {
    color: var(--brand);
    text-decoration: none;
}

.metadata-links span {
    color: var(--muted);
    font-weight: 500;
}

.code-section {
    min-width: 0;
    overflow: hidden;
    border: 1px solid #273245;
    border-radius: var(--radius-medium);
    background: var(--code);
    box-shadow: var(--shadow);
}

.code-toolbar {
    display: flex;
    min-height: 50px;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    padding: 0 16px;
    border-bottom: 1px solid #293548;
    color: #c8d0dc;
}

.code-toolbar > div {
    display: flex;
    align-items: center;
}

.window-dot {
    width: 9px;
    height: 9px;
    margin-right: 6px;
    border-radius: 50%;
}

.dot-red { background: #ff6b6b; }
.dot-yellow { background: #f6c85f; }
.dot-green { background: #59c98b; }

.code-filename {
    margin-left: 8px;
    font-family: "SFMono-Regular", Consolas, monospace;
    font-size: 12px;
}

.copy-button {
    padding: 6px 10px;
    border: 1px solid #3b4658;
    border-radius: 8px;
    background: #1a2434;
    color: #d8dee8;
    font-size: 12px;
}

.copy-button:hover,
.copy-button:focus-visible {
    border-color: #72809a;
    color: white;
}

.source-code {
    max-height: min(72vh, 920px);
    margin: 0;
    padding: 24px;
    overflow: auto;
    background: var(--code);
    color: #d9e1ec;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
    font-size: 13px;
    line-height: 1.7;
    tab-size: 4;
}

.source-code code {
    display: block;
    min-width: max-content;
}

.description-card {
    background: linear-gradient(135deg, #fff, #fafbff);
}

.solution-description,
.description-empty {
    margin: 18px 0 0;
    color: #39445a;
    white-space: pre-wrap;
}

.description-empty {
    padding: 18px;
    border-radius: 10px;
    background: var(--surface-soft);
    color: var(--muted);
}

.not-found {
    min-height: calc(100vh - 190px);
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    justify-content: center;
    padding-block: 80px;
}

.not-found h1 {
    margin: 0;
    font-size: clamp(38px, 7vw, 68px);
    letter-spacing: -0.05em;
}

.not-found > p:not(.eyebrow) {
    margin: 12px 0 28px;
    color: var(--muted);
    font-size: 18px;
}

.site-footer {
    border-top: 1px solid var(--line);
    background: var(--surface);
}

.footer-inner {
    display: flex;
    min-height: 100px;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
    color: var(--muted);
    font-size: 13px;
}

.footer-inner p {
    margin: 0;
}

:focus-visible {
    outline: 3px solid rgba(49, 87, 213, 0.35);
    outline-offset: 3px;
}

@media (max-width: 980px) {
    .filters {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .search-field {
        grid-column: 1 / -1;
    }

    .problem-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .solution-info {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 680px) {
    .shell {
        width: min(calc(100% - 28px), var(--shell));
    }

    .header-inner {
        min-height: 64px;
    }

    .brand-mark {
        width: 34px;
        height: 34px;
    }

    .header-inner {
        gap: 10px;
    }

    .brand > span:last-child {
        display: none;
    }

    .header-nav {
        gap: 2px;
    }

    .header-link,
    .header-nav-link {
        padding-inline: 8px;
        font-size: 12px;
    }

    .notice-nav-link {
        padding-right: 11px;
    }

    .header-link span[aria-hidden="true"] {
        display: none;
    }

    .hero-inner {
        padding-block: 62px 56px;
    }

    .hero-copy {
        font-size: 16px;
    }

    .stats div {
        min-width: 104px;
        flex: 1;
        padding: 12px 14px;
    }

    .catalog-section {
        padding-block: 54px 72px;
    }

    .section-heading {
        align-items: flex-start;
        flex-direction: column;
    }

    .filters,
    .problem-grid {
        grid-template-columns: 1fr;
    }

    .search-field {
        grid-column: auto;
    }

    .problem-card {
        min-height: 210px;
    }

    .pagination {
        gap: 5px;
    }

    .pagination-button {
        min-width: 38px;
        height: 38px;
        padding-inline: 9px;
        font-size: 13px;
    }

    .announcement-page {
        padding-block: 48px 72px;
    }

    .announcement-summary {
        align-items: start;
        gap: 16px;
        padding: 20px;
    }

    .announcement-summary-main {
        align-items: flex-start;
        flex-direction: column;
        gap: 7px;
    }

    .announcement-title {
        font-size: 19px;
    }

    .announcement-meta {
        gap: 12px;
    }

    .announcement-body {
        padding: 22px 20px 24px;
    }

    .problem-page {
        padding-top: 24px;
    }

    .problem-hero {
        align-items: stretch;
        flex-direction: column;
        padding: 24px;
    }

    .problem-hero .button {
        width: 100%;
    }

    .metadata-grid {
        grid-template-columns: 1fr;
    }

    .solution-info,
    .description-card {
        padding: 22px;
    }

    .source-code {
        padding: 18px;
        font-size: 12px;
    }

    .footer-inner {
        align-items: flex-start;
        flex-direction: column;
        justify-content: center;
        padding-block: 24px;
    }
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    *,
    *::before,
    *::after {
        transition-duration: 0.01ms !important;
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
    }
}