:root {
    --page: #0b0d10;
    --surface: #11151a;
    --surface-raised: #171c22;
    --line: #28303a;
    --line-soft: #1e252d;
    --text: #dce4ec;
    --muted: #94a0ad;
    --accent: #e0af68;
    --accent-bright: #f2c98a;
    --blue: #8cc8ff;
    --green: #73c991;
    --red: #f48771;
    --violet: #c586c0;
    --cyan: #4ec9b0;
    --code: #080a0d;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    color: var(--text);
    background:
        linear-gradient(rgba(224, 175, 104, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(224, 175, 104, 0.03) 1px, transparent 1px),
        var(--page);
    background-size: 32px 32px;
    font-family: "Avenir Next", Avenir, "Segoe UI", sans-serif;
    font-size: 16px;
    line-height: 1.75;
}

.progress {
    position: fixed;
    inset: 0 auto auto 0;
    z-index: 100;
    width: 0;
    height: 3px;
    background: var(--accent);
}

/* ---------------------------------------------------------------- layout */

.study-layout {
    display: grid;
    grid-template-columns: 268px minmax(0, 1fr);
    justify-content: center;
    gap: 28px;
    width: 90%;
    max-width: 1500px;
    margin: 0 auto;
    padding: 24px 0 96px;
}

.study-layout .study {
    width: auto;
    margin: 0;
    padding: 40px 0 0;
}

.study-layout .study>#table-of-contents,
.study-layout .study>.table-of-contents {
    display: none;
}

.topic-menu {
    position: sticky;
    top: 53px;
    z-index: 40;
    align-self: start;
    max-height: calc(100vh - 53px);
    overflow: auto;
    padding: 28px 14px 28px 0;
    border-right: 1px solid var(--line);
}

.topic-menu-title,
.topic-menu-panel>summary {
    margin: 0 0 12px;
    color: var(--accent);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.topic-menu-panel>summary {
    cursor: pointer;
    list-style: none;
}

.topic-menu-panel>summary::-webkit-details-marker {
    display: none;
}

.topic-menu .table-of-contents {
    display: block;
}

.topic-menu .table-of-contents a {
    padding: 4px 10px;
    color: var(--muted);
    font-size: 13px;
    line-height: 1.4;
}

.topic-menu .table-of-contents a.is-active {
    color: var(--accent-bright);
    background: rgba(224, 175, 104, 0.09);
    border-left-color: var(--accent);
}

.study {
    width: 90%;
    max-width: 1500px;
    margin: 0 auto;
    padding: 64px 0 96px;
}

.study>h1:first-child {
    margin: 0 0 20px;
    color: #f3f8fc;
    font-family: Georgia, "Times New Roman", serif;
    font-size: clamp(38px, 7vw, 68px);
    font-weight: 700;
    line-height: 1.05;
}

.study>h1:first-child::before {
    content: "Data structures & algorithms";
    display: block;
    margin-bottom: 14px;
    color: var(--accent);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

body.is-crash .study>h1:first-child::before {
    content: "DSA crash course";
}

.lede {
    max-width: 74ch;
    margin: 0 0 40px;
    color: #c6d1dc;
    font-size: 18px;
}

h2,
h3,
h4 {
    color: #f3f8fc;
    line-height: 1.25;
    scroll-margin-top: 76px;
}

h2 {
    margin: 64px 0 20px;
    padding-top: 18px;
    border-top: 1px solid var(--line);
    font-family: Georgia, "Times New Roman", serif;
    font-size: clamp(26px, 4vw, 36px);
}

h3 {
    margin: 38px 0 14px;
    font-size: 21px;
}

h4 {
    margin: 28px 0 10px;
    color: var(--accent-bright);
    font-size: 15px;
    letter-spacing: 0.01em;
}

.headerlink {
    margin-left: 8px;
    color: var(--line);
    font-family: sans-serif;
    font-size: 0.65em;
    text-decoration: none;
}

h2:hover .headerlink,
h3:hover .headerlink,
h4:hover .headerlink {
    color: var(--accent);
}

p,
ul,
ol {
    margin: 0 0 18px;
}

li+li {
    margin-top: 5px;
}

a {
    color: var(--blue);
    text-underline-offset: 3px;
}

strong {
    color: #f3f8fc;
}

hr {
    margin: 48px 0;
    border: 0;
    border-top: 1px solid var(--line);
}

/* ------------------------------------------------------- table of contents */

.table-of-contents {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 3px 28px;
    padding-left: 0;
    list-style: none;
}

.table-of-contents li,
.table-of-contents li+li {
    margin: 0;
}

.table-of-contents-numbered {
    counter-reset: toc-item;
}

.table-of-contents-numbered li {
    counter-increment: toc-item;
}

.table-of-contents-numbered a::before {
    content: counter(toc-item) ". ";
    color: var(--muted);
    font-variant-numeric: tabular-nums;
}

.table-of-contents a {
    display: block;
    padding: 5px 8px;
    border-left: 2px solid transparent;
    text-decoration: none;
}

.table-of-contents a:hover,
.table-of-contents a:focus-visible {
    color: var(--accent-bright);
    background: rgba(224, 175, 104, 0.06);
    border-left-color: var(--accent);
}

/* ------------------------------------------------------------ callouts */

blockquote {
    margin: 24px 0;
    padding: 14px 18px;
    color: #c6d1dc;
    background: rgba(224, 175, 104, 0.08);
    border-left: 3px solid var(--accent);
}

blockquote p:last-child {
    margin-bottom: 0;
}

.callout {
    margin: 24px 0;
    padding: 14px 18px 14px 46px;
    position: relative;
    color: #c6d1dc;
    background: var(--surface);
    border: 1px solid var(--line);
    border-left-width: 3px;
    border-radius: 8px;
}

.callout::before {
    position: absolute;
    top: 13px;
    left: 15px;
    font-size: 16px;
    line-height: 1.4;
}

.callout p:last-child {
    margin-bottom: 0;
}

.callout-key {
    border-left-color: var(--accent);
}

.callout-key::before {
    content: "\1F511";
}

.callout-tip {
    border-left-color: var(--green);
}

.callout-tip::before {
    content: "\1F4A1";
}

.callout-warn {
    border-left-color: var(--red);
}

.callout-warn::before {
    content: "\26A0\FE0F";
}

.callout-interview {
    border-left-color: var(--violet);
}

.callout-interview::before {
    content: "\1F3AF";
}

/* ------------------------------------------------------------ analogies */

.analogy {
    display: flex;
    gap: 16px;
    margin: 26px 0;
    padding: 16px 20px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-left: 3px solid var(--blue);
    border-radius: 10px;
}

.analogy-icon {
    flex: none;
    font-size: 26px;
    line-height: 1.3;
}

.analogy-body b {
    display: block;
    margin-bottom: 3px;
    color: var(--blue);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.analogy-body p {
    margin: 0;
    color: #c6d1dc;
}

/* -------------------------------------------------------- worked examples */

.worked {
    margin: 28px 0;
    padding: 16px 20px 18px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-left: 3px solid var(--violet);
    border-radius: 10px;
}

.worked>b:first-child {
    display: block;
    margin-bottom: 8px;
    color: var(--violet);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.worked-q {
    margin: 0 0 12px;
    color: #f3f8fc;
    font-size: 15.5px;
}

.worked-q::before {
    content: "Q.";
    margin-right: 7px;
    color: var(--violet);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-weight: 700;
}

.worked p {
    color: #c6d1dc;
}

.worked>p:last-child,
.worked>ol:last-child,
.worked>ul:last-child {
    margin-bottom: 0;
}

.worked .code-tabs {
    margin: 14px 0 0;
}

/* --------------------------------------------------------------- code */

code {
    padding: 2px 6px;
    color: var(--accent-bright);
    background: var(--surface-raised);
    border-radius: 4px;
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 0.88em;
}

pre {
    position: relative;
    margin: 22px 0;
    padding: 20px;
    overflow: hidden;
    background: var(--code);
    border: 1px solid var(--line);
    border-radius: 8px;
    box-shadow: 0 16px 38px rgba(0, 0, 0, 0.22);
}

pre::before {
    content: "";
    position: absolute;
    top: -1px;
    left: -1px;
    right: -1px;
    height: 3px;
    background: linear-gradient(90deg, var(--accent), var(--blue));
    border-top-left-radius: 8px;
    border-top-right-radius: 8px;
    pointer-events: none;
    z-index: 1;
}

pre code {
    display: block;
    overflow-x: auto;
    white-space: pre;
    padding: 0;
    color: #d8e2eb;
    background: transparent;
    border-radius: 0;
    font-size: 13px;
    line-height: 1.65;
    tab-size: 4;
}

.copy-code {
    position: absolute;
    top: 10px;
    right: 10px;
    z-index: 2;
    padding: 5px 8px;
    color: var(--muted);
    background: var(--surface-raised);
    border: 1px solid var(--line);
    border-radius: 5px;
    cursor: pointer;
    font: 600 11px "Avenir Next", Avenir, sans-serif;
}

.copy-code:hover {
    color: var(--text);
    border-color: var(--accent);
}

/* syntax tokens (emitted by the highlighter in dsa-study.js) */
.tok-com {
    color: #6a9955;
    font-style: italic;
}

.tok-kw {
    color: #c586c0;
}

.tok-typ {
    color: #4ec9b0;
}

.tok-str {
    color: #ce9178;
}

.tok-num {
    color: #b5cea8;
}

.tok-bui {
    color: #569cd6;
}

.tok-fn {
    color: #dcdcaa;
}

.tok-op {
    color: #d4d4d4;
}

.tok-pun {
    color: #ffd700;
}

.tok-var {
    color: #9cdcfe;
}

/* ------------------------------------------------------- language tabs */

.code-tabs {
    margin: 24px 0;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 10px;
    overflow: hidden;
}

.tab-bar {
    display: flex;
    gap: 2px;
    align-items: center;
    padding: 8px 10px 0;
    background: var(--surface-raised);
    border-bottom: 1px solid var(--line);
}

.tab-bar .tab-label {
    margin-right: auto;
    padding: 4px 6px 10px;
    color: var(--muted);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 11px;
    letter-spacing: 0.06em;
    text-transform: uppercase;
}

.tab {
    padding: 7px 14px 8px;
    color: var(--muted);
    background: transparent;
    border: 0;
    border-bottom: 2px solid transparent;
    cursor: pointer;
    font: 600 12px "Avenir Next", Avenir, sans-serif;
    letter-spacing: 0.03em;
}

.tab:hover {
    color: var(--text);
}

.tab[aria-selected="true"] {
    color: var(--accent-bright);
    border-bottom-color: var(--accent);
}

.code-tabs .tab-pane[hidden] {
    display: none;
}

.code-tabs pre {
    margin: 0;
    border: 0;
    border-radius: 0;
    box-shadow: none;
}

.code-tabs pre::before {
    display: none;
}

/* -------------------------------------------------------------- figures */

.figure {
    margin: 26px 0;
    padding: 20px 18px 12px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 10px;
    text-align: center;
}

.figure svg {
    max-width: 100%;
    height: auto;
}

.figure figcaption,
.viz-caption {
    margin-top: 10px;
    color: var(--muted);
    font-size: 12.5px;
    line-height: 1.6;
}

.ascii {
    margin: 22px 0;
    padding: 18px 20px;
    overflow-x: auto;
    color: #b9c6d3;
    background: var(--code);
    border: 1px solid var(--line);
    border-radius: 8px;
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 12.5px;
    line-height: 1.5;
    white-space: pre;
}

/* ----------------------------------------------------- visualisations */

.viz {
    margin: 26px 0;
    padding: 16px 18px 14px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 10px;
}

.viz-head {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: baseline;
    justify-content: space-between;
    margin-bottom: 12px;
}

.viz-title {
    color: var(--accent);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 11px;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.viz-step {
    color: var(--muted);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 11px;
    font-variant-numeric: tabular-nums;
}

.viz-stage {
    min-height: 60px;
    padding: 14px 6px;
    overflow-x: auto;
    background: var(--code);
    border: 1px solid var(--line-soft);
    border-radius: 8px;
}

.viz-note {
    min-height: 42px;
    margin-top: 10px;
    padding: 8px 12px;
    color: #c6d1dc;
    background: var(--surface-raised);
    border-left: 2px solid var(--accent);
    border-radius: 0 6px 6px 0;
    font-size: 13.5px;
    line-height: 1.55;
}

.viz-note code {
    font-size: 0.9em;
}

.viz-controls {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: center;
    margin-top: 12px;
}

.viz-btn {
    min-width: 34px;
    padding: 6px 12px;
    color: var(--text);
    background: var(--surface-raised);
    border: 1px solid var(--line);
    border-radius: 6px;
    cursor: pointer;
    font: 600 12px "Avenir Next", Avenir, sans-serif;
}

.viz-btn:hover:not(:disabled) {
    color: var(--page);
    background: var(--accent);
    border-color: var(--accent);
}

.viz-btn:disabled {
    opacity: 0.35;
    cursor: not-allowed;
}

.viz-btn.is-primary {
    color: var(--page);
    background: var(--accent);
    border-color: var(--accent);
}

.viz-scrub {
    flex: 1 1 140px;
    min-width: 120px;
    accent-color: var(--accent);
}

.viz-select {
    padding: 6px 8px;
    color: var(--text);
    background: var(--surface-raised);
    border: 1px solid var(--line);
    border-radius: 6px;
    font: 600 12px "Avenir Next", Avenir, sans-serif;
}

.viz-legend {
    display: flex;
    flex-wrap: wrap;
    gap: 6px 16px;
    margin-top: 10px;
    color: var(--muted);
    font-size: 11.5px;
}

.viz-legend span::before {
    content: "";
    display: inline-block;
    width: 10px;
    height: 10px;
    margin-right: 6px;
    border-radius: 2px;
    vertical-align: -1px;
}

.lg-cmp::before {
    background: var(--blue);
}

.lg-act::before {
    background: var(--accent);
}

.lg-done::before {
    background: var(--green);
}

.lg-out::before {
    background: var(--red);
}

.lg-idle::before {
    background: #3a4450;
}

/* array cells */

.cells {
    display: flex;
    gap: 6px;
    justify-content: center;
    min-width: min-content;
    padding: 0 8px;
}

.cell {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.cell-box {
    display: grid;
    place-items: center;
    width: 46px;
    height: 46px;
    color: var(--text);
    background: var(--surface-raised);
    border: 1px solid var(--line);
    border-radius: 6px;
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 14px;
    transition: background 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
}

.cell-idx {
    color: #5c6773;
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 10px;
}

.cell-tag {
    position: absolute;
    top: -16px;
    left: 50%;
    transform: translateX(-50%);
    color: var(--accent);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 10px;
    white-space: nowrap;
}

.cell.is-active .cell-box {
    color: var(--page);
    background: var(--accent);
    border-color: var(--accent);
    transform: translateY(-3px);
}

.cell.is-cmp .cell-box {
    color: var(--page);
    background: var(--blue);
    border-color: var(--blue);
}

.cell.is-done .cell-box {
    color: var(--page);
    background: var(--green);
    border-color: var(--green);
}

.cell.is-out .cell-box {
    color: var(--page);
    background: var(--red);
    border-color: var(--red);
}

.cell.is-window .cell-box {
    background: rgba(224, 175, 104, 0.16);
    border-color: var(--accent);
}

.cell.is-dim .cell-box {
    color: #4d5763;
    background: #10151a;
    border-color: #1c232b;
}

.cell.is-ghost .cell-box {
    color: #5c6773;
    background: transparent;
    border-style: dashed;
}

/* bar chart */

.bars {
    display: flex;
    gap: 3px;
    align-items: flex-end;
    justify-content: center;
    height: 190px;
    padding: 0 8px;
}

.bar {
    position: relative;
    display: flex;
    align-items: flex-start;
    justify-content: center;
    width: 26px;
    background: #3a4450;
    border-radius: 3px 3px 0 0;
    color: var(--page);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 10px;
    transition: height 0.16s ease, background 0.16s ease;
}

.bar span {
    position: absolute;
    top: -15px;
    color: var(--muted);
}

.bar.is-cmp {
    background: var(--blue);
}

.bar.is-act {
    background: var(--accent);
}

.bar.is-done {
    background: var(--green);
}

.bar.is-out {
    background: var(--red);
}

.bar.is-aux {
    background: var(--violet);
}

/* dp / matrix grid */

.gridviz {
    display: grid;
    gap: 3px;
    justify-content: center;
    min-width: min-content;
    padding: 0 8px;
}

.gcell {
    display: grid;
    place-items: center;
    width: 40px;
    height: 32px;
    color: var(--text);
    background: var(--surface-raised);
    border: 1px solid var(--line);
    border-radius: 4px;
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 12px;
    transition: background 0.18s ease;
}

.gcell.is-head {
    color: var(--accent);
    background: transparent;
    border-color: transparent;
    font-size: 11px;
}

.gcell.is-act {
    color: var(--page);
    background: var(--accent);
    border-color: var(--accent);
}

.gcell.is-cmp {
    color: var(--page);
    background: var(--blue);
    border-color: var(--blue);
}

.gcell.is-done {
    color: var(--page);
    background: var(--green);
    border-color: var(--green);
}

.gcell.is-empty {
    color: #3c4652;
    background: #10151a;
}

/* svg-based node graphics inside viz stages */

.viz-stage svg {
    display: block;
    margin: 0 auto;
    max-width: 100%;
    height: auto;
}

.n-idle {
    fill: var(--surface-raised);
    stroke: var(--line);
}

.n-act {
    fill: var(--accent);
    stroke: var(--accent);
}

.n-cmp {
    fill: var(--blue);
    stroke: var(--blue);
}

.n-done {
    fill: var(--green);
    stroke: var(--green);
}

.n-out {
    fill: var(--red);
    stroke: var(--red);
}

.n-label {
    fill: var(--text);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 13px;
    text-anchor: middle;
    dominant-baseline: central;
}

.n-label-dark {
    fill: var(--page);
}

.n-sub {
    fill: var(--muted);
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 10px;
    text-anchor: middle;
}

.e-idle {
    stroke: var(--line);
    stroke-width: 2;
    fill: none;
}

.e-act {
    stroke: var(--accent);
    stroke-width: 2.5;
    fill: none;
}

.e-done {
    stroke: var(--green);
    stroke-width: 2.5;
    fill: none;
}

/* ------------------------------------------------------------- tables */

.table-wrap {
    margin: 24px 0;
    overflow-x: auto;
    border: 1px solid var(--line);
    border-radius: 8px;
}

table {
    width: 100%;
    border-collapse: collapse;
    background: var(--surface);
    font-size: 14px;
}

th,
td {
    padding: 11px 14px;
    border-bottom: 1px solid var(--line);
    text-align: left;
    vertical-align: top;
}

th {
    color: var(--accent-bright);
    background: var(--surface-raised);
}

tr:last-child td {
    border-bottom: 0;
}

td code,
th code {
    white-space: nowrap;
}

/* complexity badges */

.big-o {
    display: inline-block;
    padding: 1px 8px;
    border-radius: 999px;
    font-family: ui-monospace, "SFMono-Regular", Consolas, monospace;
    font-size: 12px;
    white-space: nowrap;
}

.o-great {
    color: #9be9b4;
    background: rgba(115, 201, 145, 0.14);
}

.o-good {
    color: #b9e6c8;
    background: rgba(115, 201, 145, 0.09);
}

.o-ok {
    color: var(--accent-bright);
    background: rgba(224, 175, 104, 0.14);
}

.o-bad {
    color: #f9a58f;
    background: rgba(244, 135, 113, 0.14);
}

/* summary strip under a heading */

.meta-strip {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 10px;
    margin: 0 0 20px;
    padding: 0;
    list-style: none;
}

.meta-strip li {
    margin: 0;
    padding: 4px 12px;
    color: var(--muted);
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 999px;
    font-size: 12.5px;
}

.meta-strip li b {
    color: var(--accent-bright);
    font-weight: 600;
}

/* card grid */

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 14px;
    margin: 24px 0;
    padding: 0;
    list-style: none;
}

.card-grid li {
    margin: 0;
    padding: 14px 16px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 10px;
    font-size: 14px;
}

.card-grid li b {
    display: block;
    margin-bottom: 4px;
    color: var(--accent-bright);
}

.card-grid li.is-good {
    border-left: 3px solid var(--green);
}

.card-grid li.is-good b {
    color: #9be9b4;
}

.card-grid li.is-bad {
    border-left: 3px solid var(--red);
}

.card-grid li.is-bad b {
    color: #f9a58f;
}

/* collapsible extras */

details.extra {
    margin: 22px 0;
    padding: 0 16px;
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: 10px;
}

details.extra>summary {
    padding: 12px 0;
    color: var(--accent);
    cursor: pointer;
    font-size: 13px;
    font-weight: 600;
}

details.extra[open]>summary {
    border-bottom: 1px solid var(--line-soft);
}

details.extra[open] {
    padding-bottom: 6px;
}

/* -------------------------------------------------------------- chrome */

.study-footer {
    padding: 26px 20px;
    color: var(--muted);
    border-top: 1px solid var(--line);
    text-align: center;
    font-size: 12px;
}

.back-to-top {
    position: fixed;
    right: 18px;
    bottom: 18px;
    width: 38px;
    height: 38px;
    color: var(--page);
    background: var(--accent);
    border: 0;
    border-radius: 50%;
    cursor: pointer;
    font-size: 18px;
    font-weight: 800;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease;
}

.back-to-top.visible {
    opacity: 1;
    pointer-events: auto;
}

/* ---------------------------------------------------------- responsive */

@media (max-width: 960px) {
    .study-layout {
        display: block;
        width: 90%;
        max-width: 1500px;
        padding-top: 0;
    }

    .topic-menu {
        position: sticky;
        top: 53px;
        max-height: none;
        margin: 0 -20px 8px;
        padding: 0 20px;
        overflow: visible;
        background: var(--page);
        border-right: 0;
        border-bottom: 1px solid var(--line);
    }

    .topic-menu-panel[open] {
        padding-bottom: 12px;
    }

    .topic-menu-panel>summary {
        display: flex;
        align-items: center;
        justify-content: space-between;
        margin: 0;
        padding: 14px 0;
    }

    .topic-menu-panel>summary::after {
        content: "\25BE";
        color: var(--accent);
        font-size: 14px;
    }

    .topic-menu-panel[open]>summary::after {
        transform: rotate(180deg);
    }

    .topic-menu .table-of-contents {
        max-height: min(60vh, 420px);
        overflow: auto;
        padding-bottom: 8px;
    }
}

@media (min-width: 961px) {
    .topic-menu-panel>summary {
        cursor: default;
        pointer-events: none;
    }
}

@media (max-width: 640px) {

    .study,
    .study-layout {
        width: 90%;
        max-width: 1500px;
        padding-top: 44px;
    }

    .study-layout {
        padding-top: 0;
    }

    .study>h1:first-child {
        margin-bottom: 20px;
    }

    .table-of-contents {
        grid-template-columns: 1fr;
    }

    pre {
        padding: 18px 14px;
    }

    .cell-box {
        width: 38px;
        height: 38px;
        font-size: 12px;
    }

    .bars {
        height: 150px;
    }
}

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

    * {
        transition: none !important;
    }
}