:root {
    --ink: #071332;
    --muted: #5b6680;
    --page: #f4f8fc;
    --panel: #ffffff;
    --panel-soft: #f7fbff;
    --line: #dfe8f1;
    --blue: #2362c9;
    --blue-dark: #163f90;
    --blue-soft: #e8f0ff;
    --green: #0aa873;
    --green-dark: #087451;
    --green-soft: #e6f8f1;
    --gold: #d6a72f;
    --gold-soft: #fff6d8;
    --pink: #cf4da0;
    --pink-soft: #ffeaf6;
    --purple: #8757d4;
    --purple-soft: #f0e9ff;
    --answer: #1f7a3d;
    --answer-soft: #edf8ef;
    --answer-border: #6fbd7b;
    --shadow: 0 14px 34px rgba(45, 72, 110, 0.10);
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
    font-size: 16px;
    color: var(--ink);
    background:
        linear-gradient(180deg, rgba(229, 241, 250, 0.86), rgba(246, 249, 253, 0.94)),
        radial-gradient(circle at 12% 18%, rgba(35, 98, 201, 0.13), transparent 28%),
        radial-gradient(circle at 88% 24%, rgba(10, 168, 115, 0.11), transparent 24%),
        var(--page);
    line-height: 1.5;
}

.page-title,
.page-intro {
    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: sticky;
    top: 0;
    z-index: 20;
    background: rgba(255, 255, 255, 0.96);
    border-bottom: 1px solid var(--line);
    box-shadow: 0 3px 18px rgba(45, 72, 110, 0.08);
    backdrop-filter: blur(14px);
}

.header-inner {
    max-width: 1180px;
    min-height: 70px;
    margin: 0 auto;
    padding: 0 28px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
    color: var(--ink);
    font-weight: 800;
    font-size: 20px;
    text-decoration: none;
}

.brand-title {
    display: flex;
    align-items: baseline;
    gap: 8px;
    flex-wrap: wrap;
}

.brand-course-wrap {
    display: inline-flex;
    align-items: baseline;
    gap: 8px;
}

.brand-separator {
    color: var(--muted);
    font-weight: 700;
}

.brand-course {
    color: var(--blue-dark);
}

.brand-mark {
    position: relative;
    display: block;
    flex: 0 0 auto;
    width: 54px;
    height: 36px;
    border: 3px solid var(--blue-dark);
    border-bottom-width: 5px;
    border-radius: 4px;
}

.brand-mark::before {
    content: "</>";
    position: absolute;
    inset: 4px 7px auto;
    color: var(--blue-dark);
    font-size: 15px;
    font-weight: 900;
    line-height: 1;
}

.brand-mark::after {
    content: "";
    position: absolute;
    left: 50%;
    bottom: -11px;
    width: 38px;
    height: 5px;
    border-radius: 5px;
    background: var(--blue-dark);
    transform: translateX(-50%);
}

.site-nav {
    display: flex;
    align-items: stretch;
    gap: 28px;
    align-self: stretch;
}

.nav-link,
.course-menu summary {
    position: relative;
    display: flex;
    align-items: center;
    gap: 8px;
    color: #18213a;
    text-decoration: none;
    font-size: 15px;
    font-weight: 700;
    list-style: none;
    cursor: pointer;
}

.course-menu {
    position: relative;
    display: flex;
    align-items: stretch;
}

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

.nav-link.active {
    color: var(--blue);
}

.nav-link.active::after,
.course-menu summary.active::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: 0;
    height: 4px;
    border-radius: 4px 4px 0 0;
    background: var(--blue);
}

.course-menu-list {
    position: absolute;
    right: 0;
    top: calc(100% - 2px);
    z-index: 30;
    width: 260px;
    padding: 8px;
    border: 1px solid #cfe0f6;
    border-radius: 8px;
    background: #ffffff;
    box-shadow: 0 18px 42px rgba(45, 72, 110, 0.16);
}

.course-menu:not([open]) .course-menu-list {
    display: none;
}

.course-menu-list a {
    display: block;
    padding: 10px 12px;
    border-radius: 6px;
    color: var(--ink);
    font-weight: 700;
    text-decoration: none;
}

.course-menu-list a:hover,
.course-menu-list a:focus-visible {
    background: var(--blue-soft);
    color: var(--blue-dark);
    outline: none;
}

.nav-icon {
    position: relative;
    display: grid;
    width: 24px;
    height: 24px;
    place-items: center;
    border-radius: 50%;
    color: inherit;
    font-weight: 900;
}

.nav-icon-home::before {
    content: "";
    width: 10px;
    height: 9px;
    border: 2px solid currentColor;
    border-top: 0;
    transform: translateY(2px);
}

.nav-icon-home::after {
    content: "";
    position: absolute;
    width: 9px;
    height: 9px;
    border-left: 2px solid currentColor;
    border-top: 2px solid currentColor;
    transform: translateY(-3px) rotate(45deg);
}

.nav-icon-courses::before,
.nav-icon-courses::after {
    content: "";
    position: absolute;
    width: 14px;
    height: 10px;
    border: 2px solid currentColor;
    border-radius: 3px;
    background: #ffffff;
}

.nav-icon-courses::before {
    transform: translate(-2px, -3px);
}

.nav-icon-courses::after {
    transform: translate(3px, 3px);
}

.eyebrow {
    margin: 0 0 5px;
    color: var(--blue-dark);
    font-size: 12px;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.section-note {
    margin-bottom: 0;
    color: var(--muted);
}

main {
    max-width: 1480px;
    margin: 0 auto;
    padding: 34px 32px 44px;
}

main:has(.question-list),
main:has(.spec-section) {
    max-width: 1120px;
}

.hero {
    position: relative;
    min-height: 230px;
    padding: 28px 160px 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    overflow: hidden;
}

.hero-copy {
    position: relative;
    z-index: 2;
}

h1,
h2,
h3,
p {
    margin-top: 0;
}

h1 {
    margin-bottom: 8px;
    font-size: clamp(38px, 5vw, 58px);
    line-height: 1.04;
    letter-spacing: 0;
    color: #05082d;
}

h2 {
    margin-bottom: 4px;
    font-size: 30px;
    line-height: 1.1;
    color: inherit;
}

h3 {
    margin-bottom: 12px;
    font-size: 17px;
    line-height: 1.28;
}

.intro {
    margin-bottom: 8px;
    color: #35425a;
    font-size: 18px;
}

.courses-hero {
    margin-bottom: 22px;
    padding: 34px 0 20px;
}

.courses-hero h1 {
    max-width: 860px;
}

.courses-hero .intro {
    max-width: 820px;
    margin-bottom: 0;
}

.course-hero-j277 {
    padding-top: 12px;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 20px;
}

.course-card {
    position: relative;
    min-height: 214px;
    display: grid;
    grid-template-columns: 42px minmax(0, 1fr);
    align-content: center;
    column-gap: 18px;
    row-gap: 14px;
    padding: 26px;
    border: 1px solid #cfe0f6;
    border-radius: 8px;
    color: var(--ink);
    text-decoration: none;
    background:
        linear-gradient(90deg, rgba(35, 98, 201, 0.12), transparent 34%),
        linear-gradient(135deg, #ffffff, #edf6ff);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.course-card::before {
    content: "";
    position: absolute;
    inset: 0;
    border-left: 5px solid var(--blue);
}

.course-card:hover,
.course-card:focus-visible {
    transform: translateY(-2px);
    box-shadow: 0 18px 44px rgba(45, 72, 110, 0.16);
    outline: none;
}

.course-card strong {
    position: relative;
    z-index: 1;
    max-width: 330px;
    align-self: center;
    color: #071332;
    font-size: 26px;
    line-height: 1.12;
}

.course-card span {
    position: relative;
    z-index: 1;
}

.course-card > span:last-child {
    grid-column: 2;
    max-width: 360px;
    color: #34415b;
    font-size: 16px;
}

.course-card-icon {
    position: relative;
    grid-column: 1;
    grid-row: 1;
    align-self: center;
    z-index: 1;
    width: 36px;
    height: 30px;
    border: 3px solid currentColor;
    border-bottom-width: 5px;
    border-radius: 4px;
    color: var(--blue-dark);
    background: rgba(255, 255, 255, 0.76);
}

.course-card-icon::before {
    content: "";
    position: absolute;
    left: 50%;
    bottom: -10px;
    width: 26px;
    height: 4px;
    border-radius: 4px;
    background: currentColor;
    transform: translateX(-50%);
}

.course-card-btec {
    background:
        linear-gradient(90deg, rgba(10, 168, 115, 0.12), transparent 34%),
        linear-gradient(135deg, #ffffff, #edf9f4);
}

.course-card-btec::before {
    border-left-color: var(--green);
}

.course-card-btec .course-card-icon {
    color: var(--green-dark);
}

.course-card-ks3 {
    background:
        linear-gradient(90deg, rgba(214, 167, 47, 0.16), transparent 34%),
        linear-gradient(135deg, #ffffff, #fff8df);
}

.course-card-ks3::before {
    border-left-color: var(--gold);
}

.course-card-ks3 .course-card-icon {
    color: #765b08;
}

.empty-course-panel {
    padding: 28px;
    border: 1px solid #cfe0f6;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.86);
    box-shadow: var(--shadow);
}

.empty-course-panel h2 {
    margin-bottom: 8px;
}

.empty-course-panel p {
    margin-bottom: 0;
    color: var(--muted);
}

.lesson-header {
    margin-bottom: 20px;
    padding: 28px;
    border: 1px solid #f0b7c0;
    border-radius: 8px;
    color: #ffffff;
    background:
        radial-gradient(circle at 96% 0%, rgba(255, 255, 255, 0.2), transparent 34%),
        linear-gradient(135deg, #5d1020, #b3293d 62%, #e45565);
    box-shadow: 0 16px 34px rgba(126, 25, 43, 0.22);
}

.tasksheet-header {
    margin-bottom: 20px;
    padding: 28px;
    border: 1px solid #f0cd64;
    border-radius: 8px;
    color: #392900;
    background:
        radial-gradient(circle at 96% 0%, rgba(255, 255, 255, 0.32), transparent 34%),
        linear-gradient(135deg, #f2b51d, #ffd35a 64%, #ffe89c);
    box-shadow: 0 16px 34px rgba(175, 119, 0, 0.18);
}

.tasksheet-header .eyebrow,
.tasksheet-header .section-note {
    color: #4f3900;
}

.tasksheet-header h2 {
    color: #241800;
}

.lesson-header .eyebrow,
.lesson-header .section-note {
    color: #ffe6ea;
}

.lesson-header h2 {
    color: #ffffff;
}

.resource-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
    margin-bottom: 20px;
}

.resource-panel-wide {
    grid-column: 1 / -1;
}

.resource-panel,
.lesson-part,
.worksheet-part,
.resource-summary {
    padding: 22px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.92);
    box-shadow: var(--shadow);
}

.resource-panel h3,
.lesson-part h3,
.worksheet-part h3,
.resource-summary h3 {
    margin-top: 0;
    color: #071332;
    font-size: 22px;
}

.resource-panel ul,
.lesson-part ul,
.worksheet-part ul {
    margin-bottom: 0;
}

.part-nav {
    margin-bottom: 20px;
}

.part-nav ol {
    display: grid;
    gap: 8px;
    margin: 0;
    padding-left: 22px;
}

.part-nav a {
    display: inline;
    padding: 0;
    border: 0;
    border-radius: 0;
    color: var(--blue-dark);
    background: transparent;
    font-weight: 800;
    text-decoration: underline;
    text-underline-offset: 3px;
}

.lesson-part,
.worksheet-part {
    margin-bottom: 20px;
}

.teaching-model {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 12px;
    margin: 16px 0;
}

.model-card,
.teacher-check,
.common-mistake,
.worksheet-focus,
.visual-model {
    padding: 14px;
    border-radius: 8px;
    border: 1px solid #d7e2f0;
    background: var(--panel-soft);
}

.model-card h4,
.teacher-check h4,
.common-mistake h4 {
    margin: 0 0 8px;
    color: var(--blue-dark);
}

.model-card h4.modelling-title {
    margin-bottom: 12px;
    font-size: 22px;
    line-height: 1.2;
    text-decoration: underline;
    text-decoration-thickness: 2px;
    text-underline-offset: 5px;
}

.model-card-wide {
    grid-column: 1 / -1;
}

.common-mistake {
    border-color: #f1c26a;
    background: #fff8e7;
}

.comprehension-check {
    display: grid;
    gap: 12px;
}

.check-columns {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(260px, 0.8fr);
    gap: 20px;
    align-items: start;
}

.check-panel {
    padding: 14px;
    border: 1px solid #d7e2f0;
    border-radius: 8px;
    background: var(--panel-soft);
}

.check-panel h4 {
    margin: 0 0 12px;
    color: var(--blue-dark);
}

.comprehension-check-list {
    display: grid;
    gap: 12px;
    margin: 0;
    padding: 0;
    list-style: none;
}

.comprehension-question {
    display: grid;
    gap: 8px;
}

.comprehension-question p {
    margin: 0;
}

.comprehension-question .reveal-button {
    justify-self: start;
    min-height: 0;
    padding: 0;
    border: 0;
    border-radius: 0;
    color: #071332;
    background: transparent;
    box-shadow: none;
    font-size: 14px;
    font-weight: 400;
    text-decoration: underline;
    text-underline-offset: 3px;
}

.comprehension-question .reveal-button:hover,
.comprehension-question .reveal-button:focus {
    color: #071332;
    background: transparent;
}

.hinge-point {
    display: grid;
    gap: 10px;
}

.hinge-options {
    display: grid;
    gap: 8px;
    margin: 0;
    padding: 0;
    list-style: none;
}

.hinge-options li {
    padding: 8px 10px;
    border: 1px solid #cfe0f6;
    border-radius: 8px;
    background: #ffffff;
}

.check-answer {
    padding: 10px 12px;
    border-left: 4px solid #d73f53;
    border-radius: 8px;
    color: #5d1020;
    background: #fff0f2;
}

.check-answer.visible {
    display: block;
}

.worksheet-link-callout {
    margin-top: 16px;
    padding: 12px 14px;
    border-left: 5px solid #e6a937;
    border-radius: 8px;
    background: #fff8e7;
    font-weight: 800;
}

.bit-row,
.carry-row {
    display: grid;
    grid-template-columns: repeat(8, minmax(28px, 1fr));
    gap: 6px;
    margin: 8px 0;
}

.addition-facts-table-wrap {
    overflow-x: auto;
}

.addition-facts-table {
    width: 100%;
    border-collapse: collapse;
    background: #ffffff;
}

.addition-facts-table th,
.addition-facts-table td {
    padding: 10px 12px;
    border: 1px solid #bcd0f1;
    text-align: left;
}

.addition-facts-table th {
    color: #0d3f95;
    background: #edf4ff;
}

.addition-facts-table td:nth-child(2),
.addition-facts-table td:nth-child(3),
.addition-facts-table td:nth-child(4) {
    font-weight: 800;
}

.bit-box {
    display: grid;
    min-height: 34px;
    place-items: center;
    border: 1px solid #9db8e6;
    border-radius: 6px;
    background: #ffffff;
    font-family: Consolas, monospace;
    font-weight: 900;
}

.carry-row .bit-box {
    color: #06296a;
    border-color: #6f93d8;
    background: #dbe9ff;
}

.binary-addition-model {
    display: grid;
    gap: 7px;
}

.addition-model-row {
    display: grid;
    grid-template-columns: 96px repeat(8, minmax(34px, 1fr)) 34px;
    gap: 6px;
    align-items: center;
}

.binary-addition-model-nine .addition-model-row {
    grid-template-columns: 96px repeat(9, minmax(34px, 1fr)) 34px;
}

.addition-row-label {
    display: grid;
    min-height: 34px;
    align-items: center;
    color: var(--blue-dark);
    font-size: 13px;
    font-weight: 800;
}

.place-value-box {
    display: grid;
    min-height: 28px;
    place-items: center;
    border: 1px solid #cfe0f6;
    border-radius: 6px;
    color: #0d3f95;
    background: #edf4ff;
    font-size: 13px;
    font-weight: 800;
}

.overflow-place-value {
    color: #5d1020;
    border-color: #f0b7c0;
    background: #fff0f2;
}

.bit-box.is-active,
.place-value-box.is-active {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(43, 91, 214, 0.18);
}

.operator-cell {
    display: grid;
    min-height: 34px;
    place-items: center;
    color: var(--blue-dark);
    font-size: 24px;
    font-weight: 900;
}

.addition-result-rule {
    height: 4px;
    border-radius: 4px;
    background: var(--ink);
    margin-left: 102px;
}

.result-row .bit-box {
    color: #064b32;
    border-color: #31a46f;
    background: #e7f8ef;
}

.model-step-controls {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 14px;
    margin-top: 14px;
}

.model-step-button {
    min-width: 104px;
    border: 0;
    border-radius: 8px;
    padding: 9px 14px;
    color: #ffffff;
    background: var(--blue);
    font-weight: 800;
    cursor: pointer;
}

.model-step-button:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}

.model-step-count {
    min-width: 116px;
    text-align: center;
    color: var(--blue-dark);
    font-weight: 800;
}

.model-step-explanation {
    margin: 12px 0 0;
    padding: 10px 12px;
    border-left: 4px solid var(--blue);
    border-radius: 8px;
    background: #edf4ff;
}

.step-model-output {
    display: grid;
    gap: 8px;
}

.overflow-step-model,
.shift-step-model {
    grid-template-columns: repeat(5, minmax(0, 1fr));
}

.step-model-item {
    display: grid;
    min-height: 86px;
    align-content: center;
    gap: 4px;
    padding: 10px;
    border: 1px dashed #bcd0f1;
    border-radius: 8px;
    background: #ffffff;
    opacity: 0.28;
}

.step-model-item:not(.is-visible) > * {
    visibility: hidden;
}

.step-model-item.is-visible {
    border-style: solid;
    opacity: 1;
}

.step-model-item.is-active {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(43, 91, 214, 0.18);
}

.step-model-item strong {
    font-family: Consolas, monospace;
    color: #071332;
    font-size: 19px;
}

.step-model-item .step-label {
    color: var(--blue-dark);
    font-size: 12px;
    font-weight: 900;
    text-transform: uppercase;
}

.limit-item {
    background: #fff8e7;
}

.overflow-item {
    color: #5d1020;
    border-color: #d73f53;
    background: #fff0f2;
}

.result-shift-item {
    border-color: #31a46f;
    background: #e7f8ef;
}

.shift-place-model {
    display: grid;
    gap: 7px;
    overflow-x: auto;
    padding-bottom: 4px;
}

.shift-value-row {
    display: grid;
    grid-template-columns: 96px repeat(16, minmax(54px, 1fr));
    gap: 6px;
    align-items: stretch;
    opacity: 0.28;
}

.shift-value-row:not(.is-visible):not(.shift-place-row):not(.shift-number-row) > * {
    visibility: hidden;
}

.shift-place-row,
.shift-number-row,
.shift-value-row.is-visible {
    opacity: 1;
}

.shift-value-row.is-active .shift-cell {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(43, 91, 214, 0.18);
}

.shift-row-label,
.shift-cell {
    display: grid;
    min-height: 34px;
    place-items: center;
    border-radius: 6px;
}

.shift-row-label {
    justify-content: start;
    color: var(--blue-dark);
    font-size: 13px;
    font-weight: 900;
}

.shift-cell {
    border: 1px solid #9db8e6;
    background: #ffffff;
    font-family: Consolas, monospace;
    font-weight: 900;
}

.shift-number-row .shift-cell.has-bit {
    background: #ffffff;
}

.shift-number-row .shift-cell.outside-range {
    color: #9a1026;
    border-color: #f0b7c0;
    background: #fff0f2;
}

.shift-place-row .shift-cell {
    min-height: 30px;
    color: #0d3f95;
    border-color: #cfe0f6;
    background: #edf4ff;
    font-size: 12px;
}

.shift-cell.storage-start {
    border-left: 5px solid var(--ink);
}

.shift-cell.storage-end {
    border-right: 5px solid var(--ink);
}

.result-shift-row .shift-cell {
    color: #064b32;
    border-color: #31a46f;
    background: #e7f8ef;
}

.effect-shift-row .shift-cell {
    background: #fff8e7;
}

.shift-model {
    display: grid;
    gap: 8px;
}

.shift-line {
    display: grid;
    grid-template-columns: 90px 1fr;
    gap: 10px;
    align-items: center;
}

.worksheet-activities {
    margin-bottom: 0;
    padding-left: 0;
    list-style: none;
}

.worksheet-activities li {
    margin-bottom: 12px;
}

.worksheet-activities .reveal-button {
    display: block;
    margin-top: 8px;
}

.worksheet-activities .check-answer {
    margin-top: 8px;
}

.answer-table {
    width: 100%;
    margin: 8px 0;
    border-collapse: collapse;
    background: #ffffff;
}

.answer-table th,
.answer-table td {
    padding: 8px 10px;
    border: 1px solid #bcd0f1;
    text-align: center;
}

.answer-table th {
    color: var(--blue-dark);
    background: #edf4ff;
}

.binary-working-table th:first-child,
.binary-working-table td {
    font-family: Consolas, monospace;
    font-weight: 800;
}

.compact-answer-table {
    max-width: 420px;
}

.student-fill-table td:empty {
    min-width: 70px;
    background: #ffffff;
}

.resource-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 16px;
}

.resource-actions .action-button {
    min-width: 110px;
}

.supporting-copy {
    max-width: 720px;
    margin: 0 auto 22px;
    color: var(--muted);
    font-size: 14px;
}

.hero-art {
    position: absolute;
    z-index: 1;
    color: rgba(35, 98, 201, 0.12);
    pointer-events: none;
}

.hero-art-left {
    left: 0;
    top: 32px;
    width: 190px;
    height: 170px;
}

.hero-art-right {
    right: 0;
    top: 26px;
    width: 180px;
    height: 180px;
}

.code-window,
.brain-mark {
    position: absolute;
    display: grid;
    place-items: center;
    border: 2px solid rgba(35, 98, 201, 0.12);
    color: rgba(35, 98, 201, 0.18);
    font-weight: 800;
}

.code-window {
    left: 4px;
    top: 0;
    width: 106px;
    height: 76px;
    border-radius: 6px;
    font-size: 25px;
}

.brain-mark {
    right: 0;
    top: 0;
    width: 76px;
    height: 76px;
    border-radius: 50%;
    font-size: 17px;
    line-height: 1.2;
}

.circuit-lines,
.logic-tree {
    position: absolute;
    border-color: rgba(35, 98, 201, 0.12);
}

.circuit-lines {
    left: 56px;
    bottom: 0;
    width: 104px;
    height: 112px;
    border-left: 3px solid;
    border-top: 3px solid;
}

.circuit-lines::before,
.circuit-lines::after,
.logic-tree::before,
.logic-tree::after {
    content: "";
    position: absolute;
    border: 2px solid rgba(35, 98, 201, 0.12);
}

.circuit-lines::before {
    left: -58px;
    top: 34px;
    width: 58px;
}

.circuit-lines::after {
    left: 18px;
    top: -48px;
    height: 48px;
}

.logic-tree {
    right: 40px;
    bottom: 18px;
    width: 82px;
    height: 72px;
    border-top: 3px solid rgba(10, 168, 115, 0.13);
    border-left: 3px solid rgba(10, 168, 115, 0.13);
}

.logic-tree::before {
    right: -34px;
    top: -3px;
    width: 34px;
}

.logic-tree::after {
    left: 34px;
    bottom: -18px;
    height: 18px;
}

.quiz-type-strip {
    position: relative;
    z-index: 2;
    width: min(860px, 100%);
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    align-items: center;
    gap: 10px;
    padding: 14px 18px;
    background: rgba(255, 255, 255, 0.88);
    border: 1px solid var(--line);
    border-radius: 8px;
    box-shadow: 0 10px 26px rgba(45, 72, 110, 0.09);
}

.quiz-strip-title,
.quiz-type {
    display: inline-flex;
    align-items: center;
    min-height: 34px;
    border-radius: 999px;
    font-size: 13px;
    font-weight: 800;
    white-space: nowrap;
}

.quiz-strip-title {
    gap: 8px;
    color: var(--ink);
    padding-right: 4px;
}

.quiz-icon {
    display: grid;
    place-items: center;
    width: 28px;
    height: 28px;
    border: 2px solid #8fb5ec;
    border-radius: 7px;
    color: var(--blue);
}

.quiz-type {
    gap: 7px;
    padding: 0 13px;
    border: 1px solid transparent;
}

.quiz-type::before {
    display: grid;
    place-items: center;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    font-size: 12px;
    line-height: 1;
}

.quiz-choice {
    color: #214f92;
    background: var(--blue-soft);
}

.quiz-choice::before {
    content: "◉";
}

.quiz-check {
    color: var(--green-dark);
    background: var(--green-soft);
}

.quiz-check::before {
    content: "✓";
}

.quiz-true {
    color: #8b6d10;
    background: var(--gold-soft);
}

.quiz-true::before {
    content: "○";
}

.quiz-slider {
    color: #6b37b8;
    background: var(--purple-soft);
}

.quiz-slider::before {
    content: "↔";
}

.quiz-input {
    color: #9e2e76;
    background: var(--pink-soft);
}

.quiz-input::before {
    content: "123";
    width: auto;
    padding: 0 4px;
    border-radius: 5px;
    font-size: 10px;
}

.view {
    display: none;
}

.active-view {
    display: block;
}

.paper-section {
    margin-bottom: 28px;
    padding: 0;
    background: transparent;
    border: 0;
    border-radius: 0;
    box-shadow: none;
}

#paper-2 {
    background: transparent;
}

.section-heading {
    display: flex;
    align-items: center;
    gap: 14px;
    margin: 0 0 18px;
    padding: 0 0 2px;
}

.section-heading h2 {
    margin: 0;
    color: var(--blue-dark);
    font-size: 30px;
    line-height: 1.16;
}

#paper-2 .section-heading h2 {
    color: var(--green-dark);
}

.section-heading p {
    order: -1;
    margin-bottom: 2px;
    color: inherit;
    font-size: 28px;
    line-height: 1;
    font-weight: 900;
}

.paper-icon {
    position: static;
    flex: 0 0 auto;
    display: grid;
    width: 48px;
    height: 48px;
    place-items: center;
    border-radius: 50%;
    color: #ffffff;
}

.paper-1-icon {
    background: linear-gradient(135deg, var(--blue), var(--blue-dark));
}

.paper-2-icon {
    background: linear-gradient(135deg, var(--green), var(--green-dark));
}

.paper-icon::before {
    font-size: 28px;
    font-weight: 900;
}

.paper-1-icon::before {
    content: "▣";
}

.paper-2-icon::before {
    content: "</>";
    font-size: 20px;
}

.topic-grid {
    display: grid;
    align-items: start;
    gap: 26px;
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

.topic-card,
.question-card,
.question-header,
.spec-card {
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.topic-card {
    position: relative;
    min-height: 0;
    padding: 28px 18px 20px;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.topic-card::before {
    content: "";
    position: absolute;
    inset: 0 0 auto;
    height: 4px;
    background: var(--blue);
}

#paper-2 .topic-card::before,
.topic-card:nth-child(3n)::before {
    background: var(--green);
}

.topic-card-header {
    display: flex;
    align-items: center;
    gap: 14px;
    min-height: 58px;
    margin-bottom: 22px;
}

.topic-card-header > div {
    min-width: 0;
}

.topic-icon {
    flex: 0 0 auto;
    display: grid;
    width: 50px;
    height: 50px;
    margin-bottom: 0;
    place-items: center;
    border-radius: 50%;
    color: #ffffff;
    background: linear-gradient(135deg, var(--blue), var(--blue-dark));
}

#paper-2 .topic-icon {
    color: #ffffff;
    background: linear-gradient(135deg, var(--green), var(--green-dark));
}

.topic-icon svg {
    width: 31px;
    height: 31px;
    fill: none;
    stroke: currentColor;
    stroke-width: 1.9;
    stroke-linecap: round;
    stroke-linejoin: round;
}

.topic-number {
    display: inline;
    margin: 0 8px 0 0;
    color: var(--blue-dark);
    font-size: 25px;
    font-weight: 900;
}

.topic-card h3 {
    display: inline;
    margin: 0;
    color: var(--ink);
    font-size: 25px;
    line-height: 1.18;
}

.topic-list {
    display: grid;
    gap: 16px;
    list-style: none;
    margin: 0;
    padding: 0;
}

.topic-list li {
    min-height: 74px;
    display: grid;
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: center;
    gap: 14px;
    padding: 14px 12px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: linear-gradient(180deg, #ffffff, #f9fcff);
    box-shadow: 0 8px 20px rgba(45, 72, 110, 0.05);
    min-width: 0;
}

.back-button,
.reveal-button,
.action-button {
    font-family: Arial, Helvetica, sans-serif;
}

.topic-title {
    display: block;
    width: 100%;
    color: #0d214b;
    text-align: left;
    font-size: 16px;
    line-height: 1.3;
}

.topic-title strong {
    font-weight: 900;
}

.topic-count {
    margin: 0 0 12px;
    color: var(--muted);
    font-size: 13px;
    font-weight: 700;
}

.topic-actions {
    display: flex;
    flex-wrap: nowrap;
    justify-content: stretch;
    gap: 8px;
    margin-top: 0;
    min-width: 0;
    width: 420px;
    max-width: 100%;
}

.action-button {
    display: inline-flex;
    min-width: 0;
    min-height: 34px;
    align-items: center;
    justify-content: center;
    gap: 8px;
    border: 0;
    border-radius: 7px;
    color: #ffffff;
    font-size: 12px;
    font-weight: 900;
    text-decoration: none;
    cursor: pointer;
}

.topic-actions .action-button {
    flex: 1 1 0;
}

.action-button::before {
    display: inline-grid;
    width: 16px;
    height: 16px;
    place-items: center;
    font-size: 15px;
    line-height: 1;
}

.learn-button {
    color: #8b1d2c;
    background: linear-gradient(180deg, #ffe3e8, #f7b8c4);
    box-shadow: inset 0 0 0 1px rgba(184, 54, 73, 0.22);
}

.learn-button::before {
    content: "\1F393";
    font-size: 14px;
}

.worksheet-button {
    color: #5f4200;
    background: linear-gradient(180deg, #ffe073, #f4b51f);
    box-shadow: inset 0 0 0 1px rgba(158, 107, 0, 0.22);
}

.worksheet-button::before {
    content: "\1F4A1";
    font-size: 14px;
}

.qa-button {
    background: linear-gradient(180deg, #2870e8, #1748a8);
}

.qa-button::before {
    content: "\270E";
    font-size: 15px;
}

.quiz-button {
    background: linear-gradient(180deg, #10b881, #079a68);
}

.quiz-button::before {
    content: "?";
    font-size: 15px;
    font-weight: 900;
}

.quiz-button:disabled {
    opacity: 0.7;
    cursor: not-allowed;
}
.back-link {
    display: inline-block;
    text-decoration: none;
}

.back-button {
    margin-bottom: 22px;
    border: none;
    border-radius: 8px;
    background: var(--blue-dark);
    color: #ffffff;
    padding: 10px 16px;
    font-size: 16px;
    font-weight: bold;
    box-shadow: 0 8px 18px rgba(22, 63, 144, 0.18);
    cursor: pointer;
}

.back-button:hover,
.back-button:focus {
    background: var(--blue);
}

.question-header {
    margin-bottom: 22px;
    padding: 22px;
    background:
        radial-gradient(circle at 96% 0%, rgba(10, 168, 115, 0.24), transparent 34%),
        linear-gradient(135deg, #071332, #123f78);
    color: #ffffff;
    border-color: rgba(255, 255, 255, 0.12);
    box-shadow: 0 16px 34px rgba(7, 19, 50, 0.22);
}

.question-header .eyebrow {
    color: #9fc5ff;
}

.question-header .section-note {
    color: #d9e7ff;
}

body:has(.quiz-form) .question-header {
    background:
        radial-gradient(circle at 96% 0%, rgba(255, 255, 255, 0.2), transparent 34%),
        linear-gradient(135deg, #053b2c, #07865d 62%, #10b881);
    box-shadow: 0 16px 34px rgba(7, 128, 88, 0.24);
}

body:has(.quiz-form) .question-header .eyebrow {
    color: #b8f5df;
}

body:has(.quiz-form) .question-header .section-note {
    color: #e2fff3;
}

.quiz-timer {
    display: grid;
    gap: 2px;
    justify-items: center;
    padding: 14px 16px;
    border: 1px solid rgba(255, 255, 255, 0.48);
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.16);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.22);
}

.quiz-timer-floating {
    position: fixed;
    top: 214px;
    right: max(24px, calc((100vw - 1180px) / 2 - 260px));
    z-index: 12;
    width: 210px;
    background:
        radial-gradient(circle at 100% 0%, rgba(255, 255, 255, 0.34), transparent 44%),
        linear-gradient(135deg, #00a875, #2362c9 56%, #8757d4);
    border-color: rgba(255, 255, 255, 0.42);
    box-shadow: 0 18px 36px rgba(35, 98, 201, 0.28);
}

.quiz-timer span {
    color: #f7fbff;
    font-size: 13px;
    font-weight: 900;
    letter-spacing: 0.04em;
    text-transform: uppercase;
}

.quiz-timer strong {
    color: #ffffff;
    font-size: 23px;
    line-height: 1.15;
    text-align: center;
    white-space: nowrap;
}

@media (max-width: 1560px) {
    body:has(.quiz-form) main {
        padding-bottom: 96px;
    }

    .quiz-timer-floating {
        top: auto;
        right: 18px;
        bottom: 18px;
        width: auto;
        min-width: 190px;
        grid-template-columns: auto auto;
        align-items: baseline;
        justify-items: start;
        column-gap: 10px;
        padding: 10px 13px;
        border-radius: 999px;
    }

    .quiz-timer strong {
        font-size: 20px;
    }
}

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

.quiz-form {
    display: grid;
    gap: 18px;
}

.question-card {
    padding: 22px;
    border-left: 6px solid var(--gold);
}

.quiz-question {
    display: grid;
    gap: 12px;
    padding: 22px;
    background: var(--panel);
    border: 1px solid var(--line);
    border-left: 6px solid var(--blue);
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.quiz-question h3 {
    margin-bottom: 2px;
    font-size: 20px;
}

.quiz-question label {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 14px;
    border: 1px solid #c7d8ef;
    border-radius: 10px;
    background: linear-gradient(180deg, #ffffff, #f5f9ff);
    color: #10234f;
    font-weight: 700;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.9), 0 3px 10px rgba(35, 98, 201, 0.06);
    cursor: pointer;
    transition: border-color 0.16s ease, box-shadow 0.16s ease, background 0.16s ease, transform 0.16s ease;
}

.quiz-question label:hover {
    border-color: var(--blue);
    background: linear-gradient(180deg, #ffffff, #eef5ff);
    box-shadow: 0 6px 16px rgba(35, 98, 201, 0.12);
}

.quiz-question label:has(input:checked) {
    border-color: var(--blue);
    background: linear-gradient(180deg, #eaf2ff, #dfeaff);
    color: var(--blue-dark);
    box-shadow: 0 0 0 2px rgba(35, 98, 201, 0.10), 0 7px 18px rgba(35, 98, 201, 0.13);
}

.quiz-question label:has(input:focus-visible) {
    outline: 3px solid rgba(35, 98, 201, 0.22);
    outline-offset: 2px;
}

.quiz-question input[type="radio"],
.quiz-question input[type="checkbox"] {
    flex: 0 0 auto;
    width: 20px;
    height: 20px;
    accent-color: var(--blue);
}

.quiz-question input[type="text"] {
    width: min(100%, 360px);
    min-height: 48px;
    border: 1px solid #b9cdec;
    border-radius: 10px;
    background: linear-gradient(180deg, #ffffff, #f4f8ff);
    color: #10234f;
    font: inherit;
    font-weight: 800;
    padding: 0 14px;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85), 0 3px 10px rgba(35, 98, 201, 0.08);
}

.quiz-question input[type="text"]:focus {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(35, 98, 201, 0.16);
    outline: none;
}

.quiz-question.is-correct {
    border-left-color: var(--green);
}

.quiz-question.is-incorrect {
    border-left-color: #d64242;
}

.quiz-feedback {
    margin-bottom: 0;
    padding: 10px 12px;
    border-radius: 8px;
    background: var(--blue-soft);
    color: var(--blue-dark);
    font-weight: 700;
}

.quiz-question.is-correct .quiz-feedback {
    background: var(--green-soft);
    color: var(--green-dark);
}

.quiz-question.is-incorrect .quiz-feedback {
    background: #fff0f0;
    color: #8e2020;
}

.slider-question {
    display: grid;
    gap: 12px;
    max-width: 430px;
    padding: 16px;
    border: 1px solid #c7d8ef;
    border-radius: 12px;
    background: linear-gradient(180deg, #ffffff, #f5f9ff);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.9), 0 3px 10px rgba(35, 98, 201, 0.06);
}

.slider-question input[type="range"] {
    width: 100%;
    height: 28px;
    appearance: none;
    background: transparent;
    cursor: pointer;
}

.slider-question input[type="range"]::-webkit-slider-runnable-track {
    height: 10px;
    border: 1px solid #b9cdec;
    border-radius: 999px;
    background: linear-gradient(90deg, var(--blue), #8fb5ec);
    box-shadow: inset 0 1px 2px rgba(7, 19, 50, 0.18);
}

.slider-question input[type="range"]::-webkit-slider-thumb {
    appearance: none;
    width: 26px;
    height: 26px;
    margin-top: -9px;
    border: 3px solid #ffffff;
    border-radius: 50%;
    background: var(--blue);
    box-shadow: 0 4px 12px rgba(35, 98, 201, 0.35);
}

.slider-question input[type="range"]::-moz-range-track {
    height: 10px;
    border: 1px solid #b9cdec;
    border-radius: 999px;
    background: linear-gradient(90deg, var(--blue), #8fb5ec);
    box-shadow: inset 0 1px 2px rgba(7, 19, 50, 0.18);
}

.slider-question input[type="range"]::-moz-range-thumb {
    width: 22px;
    height: 22px;
    border: 3px solid #ffffff;
    border-radius: 50%;
    background: var(--blue);
    box-shadow: 0 4px 12px rgba(35, 98, 201, 0.35);
}

.slider-question input[type="range"]:focus-visible {
    outline: 3px solid rgba(35, 98, 201, 0.22);
    outline-offset: 6px;
}

.slider-labels {
    display: flex;
    justify-content: space-between;
    color: var(--blue-dark);
    font-weight: 900;
}

.matching-grid {
    display: grid;
    gap: 12px;
}

.matching-grid label,
.match-row {
    display: grid;
    grid-template-columns: minmax(120px, 180px) minmax(0, 1fr);
    align-items: center;
    font-weight: 800;
}

.match-row {
    grid-template-columns: minmax(130px, 170px) minmax(0, 1fr);
    gap: 12px;
    padding: 12px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: var(--panel-soft);
}

.match-row p {
    margin-bottom: 0;
    font-weight: 700;
}

.structure-diagram {
    margin: 4px 0 18px;
    padding: 22px 18px;
    border: 1px solid #c8d7ea;
    border-radius: 8px;
    background:
        linear-gradient(90deg, rgba(35, 98, 201, 0.03) 1px, transparent 1px) 0 0 / 32px 32px,
        linear-gradient(180deg, #ffffff, #f7fbff);
    overflow-x: auto;
}

.structure-tree {
    min-width: max-content;
    display: flex;
    justify-content: center;
    padding: 2px 10px 8px;
}

.structure-tree ul {
    position: relative;
    display: flex;
    justify-content: center;
    gap: 18px;
    margin: 0;
    padding: 42px 0 0;
    list-style: none;
}

.structure-tree > ul {
    padding-top: 0;
}

.structure-tree li {
    position: relative;
    display: grid;
    justify-items: center;
    align-content: start;
    min-width: 138px;
    padding: 0 4px;
}

.structure-tree li::before,
.structure-tree li::after {
    content: "";
    position: absolute;
    top: 0;
    width: calc(50% + 9px);
    height: 22px;
    border-top: 1px solid #7f98bb;
}

.structure-tree li::before {
    right: 50%;
}

.structure-tree li::after {
    left: 50%;
    border-left: 1px solid #7f98bb;
}

.structure-tree li:only-child::before,
.structure-tree li:only-child::after {
    display: none;
}

.structure-tree li:first-child::before,
.structure-tree li:last-child::after {
    border-top: 0;
}

.structure-tree li:first-child::after {
    border-top-left-radius: 8px;
}

.structure-tree li:last-child::before {
    border-top-right-radius: 8px;
}

.structure-tree ul ul::before {
    content: "";
    position: absolute;
    top: 20px;
    left: 50%;
    height: 22px;
    border-left: 1px solid #7f98bb;
}

.structure-node {
    position: relative;
    display: grid;
    place-items: center;
    min-width: 130px;
    max-width: 190px;
    min-height: 42px;
    padding: 10px 12px;
    border: 1px solid #8ca4c4;
    border-radius: 4px;
    background: #ffffff;
    color: #0d214b;
    text-align: center;
    font-size: 14px;
    font-weight: 800;
    line-height: 1.2;
    box-shadow: none;
}

.structure-node.root {
    border-color: #079a68;
    background: linear-gradient(180deg, #ecfff8, #ffffff);
    color: #053b2c;
}

.structure-node.blank-node {
    border-style: dashed;
    background: #f8fbff;
    color: #6a7a99;
}

.structure-tree .drop-blank {
    min-width: 138px;
    max-width: 190px;
    min-height: 42px;
    margin: 0;
    padding: 10px 12px;
    border: 2px dashed #7fafef;
    border-radius: 4px;
    background: #f8fbff;
    color: var(--blue-dark);
    font-size: 14px;
    font-weight: 900;
    line-height: 1.2;
}

.structure-tree .drop-blank.is-hovered {
    border-color: var(--blue);
    background: var(--blue-soft);
}

.structure-node.is-highlighted {
    border-color: #ebbd1f;
    background: #fff9db;
    color: #765b08;
}

.structure-node.small {
    min-width: 112px;
    min-height: 38px;
    padding: 8px 10px;
    font-size: 14px;
}

.structure-node.problem-node {
    border-color: #38557d;
    background: #eef5ff;
    color: #0d214b;
}

.structure-caption {
    margin: -4px 0 0;
    color: var(--muted);
    font-size: 13px;
    font-weight: 800;
    text-align: center;
}

@media (max-width: 700px) {
    .structure-diagram {
        padding: 12px;
        overflow-x: visible;
    }

    .structure-tree {
        display: block;
        min-width: 0;
        padding-inline: 4px;
    }

    .structure-tree ul {
        display: grid;
        justify-content: stretch;
        gap: 12px;
        min-width: 0;
        padding: 16px 0 0 24px;
    }

    .structure-tree > ul {
        padding: 0;
    }

    .structure-tree li {
        justify-items: start;
        min-width: 0;
        padding-left: 18px;
    }

    .structure-tree > ul > li {
        padding-left: 0;
    }

    .structure-tree li::before,
    .structure-tree li::after {
        display: none;
    }

    .structure-tree ul ul::before {
        top: 0;
        bottom: 0;
        left: 8px;
        height: auto;
    }

    .structure-tree ul ul > li::before {
        content: "";
        position: absolute;
        display: block;
        top: 20px;
        left: -16px;
        width: 16px;
        height: 0;
        border-top: 1px solid #7f98bb;
    }

    .structure-node {
        width: min(100%, 230px);
        min-width: 0;
        max-width: 230px;
        min-height: 38px;
        padding: 8px 9px;
        font-size: 13px;
    }

    .structure-tree .drop-blank {
        width: min(100%, 230px);
        min-width: 0;
        max-width: 230px;
        min-height: 38px;
        padding: 8px 9px;
        font-size: 13px;
    }
}

.matching-grid select {
    width: 100%;
    min-height: 40px;
    border: 1px solid var(--line);
    border-radius: 8px;
    background: #ffffff;
    color: var(--ink);
    font: inherit;
}

.quiz-table-wrap {
    overflow-x: auto;
}

.quiz-table {
    width: 100%;
    min-width: 520px;
    border-collapse: separate;
    border-spacing: 0;
    border: 1px solid var(--line);
    border-radius: 8px;
    overflow: hidden;
    background: #ffffff;
}

.quiz-table th,
.quiz-table td {
    padding: 14px 12px;
    border-bottom: 1px solid var(--line);
    text-align: left;
    vertical-align: middle;
}

.quiz-table tr:last-child th,
.quiz-table tr:last-child td {
    border-bottom: 0;
}

.quiz-table thead th {
    background: var(--blue-soft);
    color: var(--blue-dark);
}

.quiz-table tbody th {
    width: 34%;
    color: var(--ink);
}

.quiz-table select {
    width: 100%;
    min-height: 46px;
    appearance: none;
    border: 1px solid #b9cdec;
    border-radius: 10px;
    background:
        linear-gradient(45deg, transparent 50%, var(--blue-dark) 50%) calc(100% - 20px) 50% / 7px 7px no-repeat,
        linear-gradient(135deg, var(--blue-dark) 50%, transparent 50%) calc(100% - 15px) 50% / 7px 7px no-repeat,
        linear-gradient(180deg, #ffffff, #f4f8ff);
    color: #10234f;
    font: inherit;
    font-weight: 800;
    padding: 0 46px 0 14px;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85), 0 3px 10px rgba(35, 98, 201, 0.08);
    cursor: pointer;
}

.quiz-table select:hover {
    border-color: var(--blue);
    background-color: #f8fbff;
}

.quiz-table select:focus {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(35, 98, 201, 0.16);
    outline: none;
}

.trace-table-input {
    width: 92px;
    min-height: 42px;
    border: 2px dashed #9fc5ff;
    border-radius: 8px;
    background: #ffffff;
    color: var(--blue-dark);
    font: inherit;
    font-weight: 900;
    padding: 6px 10px;
    text-align: center;
}

.trace-table-input:focus {
    border-style: solid;
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(35, 98, 201, 0.16);
    outline: none;
}

.quiz-table td.trace-given {
    color: var(--blue-dark);
    font-weight: 900;
    text-align: center;
}

.word-bank {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.drag-word {
    border: 1px solid #8acfb8;
    border-radius: 999px;
    background: var(--green-soft);
    color: var(--green-dark);
    padding: 8px 13px;
    font: inherit;
    font-weight: 900;
    max-width: 100%;
    white-space: normal;
    overflow-wrap: anywhere;
    cursor: grab;
}

.drag-word:nth-child(4n + 2) {
    border-color: #ebcf69;
    background: var(--gold-soft);
    color: #765b08;
}

.drag-word:nth-child(4n + 3) {
    border-color: #efa3a3;
    background: #fff0f0;
    color: #8e2020;
}

.drag-word:nth-child(4n) {
    border-color: #c3a8ee;
    background: var(--purple-soft);
    color: #583297;
}

.drag-word:hover,
.drag-word:focus-visible {
    transform: translateY(-1px);
    box-shadow: 0 8px 18px rgba(45, 72, 110, 0.14);
}

.drag-word:active {
    cursor: grabbing;
}

.blank-paragraph {
    margin-bottom: 0;
    font-size: 18px;
    line-height: 2.35;
}

.compact-blank-paragraph {
    line-height: 2.05;
}

.inline-blank-select {
    min-width: 170px;
    min-height: 40px;
    appearance: none;
    margin: 0 4px;
    border: 1px solid #b9cdec;
    border-radius: 10px;
    background:
        linear-gradient(45deg, transparent 50%, var(--blue-dark) 50%) calc(100% - 18px) 50% / 7px 7px no-repeat,
        linear-gradient(135deg, var(--blue-dark) 50%, transparent 50%) calc(100% - 13px) 50% / 7px 7px no-repeat,
        linear-gradient(180deg, #ffffff, #f4f8ff);
    color: #10234f;
    font: inherit;
    font-weight: 800;
    padding: 0 40px 0 12px;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.85), 0 3px 10px rgba(35, 98, 201, 0.08);
    cursor: pointer;
    vertical-align: middle;
}

.inline-blank-select:hover {
    border-color: var(--blue);
}

.inline-blank-select:focus {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(35, 98, 201, 0.16);
    outline: none;
}

.pseudocode-fill {
    display: grid;
    gap: 10px;
    padding: 18px;
    border: 1px solid #d7e4f7;
    border-radius: 8px;
    background:
        linear-gradient(90deg, rgba(35, 98, 201, 0.04) 1px, transparent 1px) 0 0 / 32px 32px,
        linear-gradient(180deg, #ffffff, #f8fbff);
    overflow-x: auto;
}

.pseudocode-fill p {
    min-width: max-content;
    margin: 0;
    color: #071332;
    font-family: Consolas, "Courier New", monospace;
    font-size: 18px;
    line-height: 2.15;
    white-space: nowrap;
}

.flowchart-diagram {
    display: grid;
    gap: 16px;
    margin: 6px 0 14px;
    padding: 18px;
    border: 1px solid #cfe0f6;
    border-radius: 8px;
    background: linear-gradient(180deg, #ffffff, #f4fbf8);
    overflow-x: auto;
}

.flow-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    min-width: max-content;
}

.flow-node {
    display: inline-grid;
    place-items: center;
    min-width: 126px;
    min-height: 44px;
    padding: 9px 14px;
    border: 2px solid #8fb5ec;
    background: #ffffff;
    color: #0d214b;
    font-weight: 900;
    text-align: center;
    box-shadow: 0 8px 18px rgba(45, 72, 110, 0.08);
}

.flow-node.terminal {
    border-color: #07865d;
    border-radius: 999px;
    background: #ecfff8;
    color: #053b2c;
}

.flow-node.process {
    border-radius: 8px;
}

.flow-node.io {
    transform: skewX(-10deg);
    border-color: #ebbd1f;
    background: #fff9db;
    color: #765b08;
}

.flow-node.io,
.flow-node.io * {
    transform-origin: center;
}

.flow-node.decision {
    min-width: 112px;
    min-height: 68px;
    clip-path: polygon(50% 0, 100% 50%, 50% 100%, 0 50%);
    border-color: #c3a8ee;
    background: #f7f1ff;
    color: #583297;
    padding: 14px 24px;
}

.flow-node.decision {
    font-size: 13px;
}

.flow-node.sub {
    border-left-width: 8px;
    border-right-width: 8px;
}

.flow-arrow {
    color: var(--blue);
    font-weight: 900;
}

@media (max-width: 700px) {
    .pseudocode-fill {
        padding: 12px;
    }

    .pseudocode-fill p {
        font-size: 15px;
    }

    .flowchart-diagram {
        padding: 12px;
    }

    .flow-row {
        justify-content: flex-start;
    }

    .flow-node {
        min-width: 108px;
        font-size: 13px;
    }
}

.quiz-question[data-type="drag-blank"] {
    gap: 18px;
    padding-bottom: 30px;
}

.drop-blank,
.match-drop {
    display: inline-grid;
    min-width: 140px;
    min-height: 34px;
    margin: 6px 4px;
    padding: 2px 10px;
    place-items: center;
    border: 2px dashed #9fc5ff;
    border-radius: 8px;
    background: var(--panel-soft);
    color: var(--blue-dark);
    font-weight: 900;
    vertical-align: middle;
}

.match-drop {
    width: 100%;
    margin: 0;
}

.drop-blank.is-hovered,
.match-drop.is-hovered {
    background: var(--blue-soft);
    border-color: var(--blue);
}

.quiz-controls {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 14px;
}

.quiz-controls .back-button {
    margin-bottom: 0;
}

.quiz-result {
    margin-bottom: 0;
    color: var(--blue-dark);
    font-size: 20px;
    font-weight: 900;
}

.question-text {
    margin-bottom: 0;
    font-size: 20px;
    font-weight: normal;
    color: var(--ink);
}

.question-text strong {
    color: var(--blue);
    font-weight: bold;
}

.question-requirements {
    margin: 12px 0 0 0;
    padding-left: 22px;
    color: var(--ink);
}

.question-requirements li {
    margin-bottom: 6px;
}

.question-figure {
    margin: 16px 0;
}

.question-figure img {
    max-width: 100%;
    height: auto;
    display: block;
    border: 1px solid var(--line);
    border-radius: 8px;
}

.question-figure figcaption {
    margin-top: 8px;
    font-size: 14px;
    color: var(--muted);
}

.gate-symbol-card {
    display: inline-grid;
    grid-template-columns: minmax(96px, 140px) auto;
    align-items: center;
    gap: 12px;
}

.gate-symbol-card svg {
    width: 120px;
    max-width: 100%;
    height: auto;
    stroke: currentColor;
    stroke-width: 3;
    fill: none;
}

.logic-figure-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
}

.ide-mockup {
    display: grid;
    gap: 0;
    margin: 8px 0 12px;
    border: 1px solid #c7d8ef;
    border-radius: 8px;
    overflow: hidden;
    background: #ffffff;
}

.ide-toolbar,
.ide-errors {
    padding: 10px 12px;
    background: var(--blue-soft);
    color: var(--blue-dark);
    font-weight: 900;
}

.ide-layout {
    display: grid;
    grid-template-columns: minmax(0, 2fr) minmax(140px, 1fr);
}

.ide-editor,
.ide-output {
    padding: 14px;
    min-height: 120px;
    font-family: Consolas, "Courier New", monospace;
}

.ide-editor {
    border-right: 1px solid var(--line);
    background:
        linear-gradient(90deg, rgba(35, 98, 201, 0.04) 1px, transparent 1px) 0 0 / 32px 32px,
        #ffffff;
}

.ide-output {
    background: #f7fbff;
}

.algorithm-code {
    margin: 14px 0;
    padding: 14px 16px;
    overflow-x: auto;
    background: #0f2230;
    color: #f4fbfd;
    border-radius: 8px;
    font-size: 15px;
    line-height: 1.5;
}

.algorithm-code code {
    font-family: Consolas, "Courier New", monospace;
}

.code-keyword {
    color: #78dce8;
    font-weight: 700;
}

.code-string {
    color: #ffd479;
}

.code-number,
.code-boolean {
    color: #a9dc76;
}

.code-function {
    color: #ab9df2;
}

.code-operator {
    color: #ff6188;
}

.code-comment {
    color: #9aaeb8;
    font-style: italic;
}

.trace-table-wrap,
.spec-table-wrap {
    margin: 14px 0;
    overflow-x: auto;
}

.trace-table,
.spec-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--panel);
    border: 1px solid var(--line);
}

.trace-table {
    min-width: 520px;
}

.spec-table {
    min-width: 720px;
    border-radius: 8px;
    box-shadow: var(--shadow);
    overflow: hidden;
}

.trace-table caption {
    margin-bottom: 8px;
    color: var(--muted);
    font-size: 14px;
    text-align: left;
}

.trace-table th,
.trace-table td,
.spec-table th,
.spec-table td {
    padding: 10px 12px;
    border: 1px solid var(--line);
    text-align: left;
    vertical-align: top;
}

.trace-table th {
    background: var(--blue-soft);
    color: var(--blue-dark);
}

.spec-table thead th {
    background: var(--blue-dark);
    color: #ffffff;
}

.spec-table tbody th,
.spec-card h3 {
    color: var(--blue-dark);
}

.spec-table tr:last-child th,
.spec-table tr:last-child td {
    border-bottom: none;
}

.reveal-button {
    margin-top: 12px;
    border: 1px solid var(--line);
    border-radius: 999px;
    background: #f5f9fb;
    color: var(--muted);
    padding: 6px 11px;
    font-size: 14px;
    font-weight: 600;
    box-shadow: none;
    cursor: pointer;
}

.reveal-button:hover,
.reveal-button:focus {
    background: var(--blue-soft);
    border-color: var(--blue);
    color: var(--blue-dark);
}

.mark-scheme {
    display: none;
    margin-top: 16px;
    padding: 16px;
    border-left: 5px solid var(--answer-border);
    background: var(--answer-soft);
    color: #245232;
    border-radius: 0 8px 8px 0;
}

.mark-scheme.visible {
    display: block;
}

.mark-scheme h4 {
    margin: 0 0 8px 0;
    font-size: 18px;
    color: var(--answer);
}

.mark-scheme-intro {
    margin-bottom: 8px;
    color: #245232;
}

.mark-scheme ul,
.mark-scheme ol {
    margin-bottom: 0;
    padding-left: 22px;
}

.mark-scheme li {
    margin-bottom: 6px;
}

.spec-section {
    margin-bottom: 34px;
}

.spec-grid {
    display: grid;
    gap: 18px;
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

.spec-card {
    padding: 22px;
}

.spec-card ul {
    margin: 0;
    padding-left: 22px;
}

.spec-card li {
    margin-bottom: 8px;
}

.spec-note {
    margin-top: 14px;
    color: var(--muted);
}

footer {
    width: 100%;
    margin: 0;
    padding: 0;
    color: var(--muted);
    text-align: center;
    background: rgba(255, 255, 255, 0.88);
    border-top: 1px solid var(--line);
}

footer p {
    max-width: 1180px;
    margin: 0 auto;
    margin-bottom: 0;
    padding: 18px 28px;
}

footer .footer-small {
    font-size: 13px;
}

footer a {
    color: var(--blue-dark);
    font-weight: 700;
}

@media (max-width: 1040px) {
    .hero {
        padding-inline: 86px;
    }

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

    .course-card {
        min-height: 220px;
    }

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

@media (max-width: 760px) {
    html,
    body {
        max-width: 100%;
        overflow-x: hidden;
    }

    .header-inner {
        min-height: auto;
        padding: 12px 18px;
        flex-direction: column;
        align-items: flex-start;
        gap: 12px;
    }

    .brand {
        font-size: 16px;
    }

    .brand-title {
        line-height: 1.25;
    }

    .brand-mark {
        width: 46px;
        height: 32px;
    }

    .site-nav {
        width: 100%;
        min-height: 42px;
        gap: 22px;
    }

    .course-menu-list {
        left: 0;
        right: auto;
        width: min(280px, calc(100vw - 36px));
    }

    main {
        width: 100%;
        max-width: 100vw;
        padding: 18px 14px 34px;
        overflow-x: hidden;
    }

    body:has(.quiz-form) main {
        width: 100%;
        max-width: 100vw;
        overflow-x: hidden;
    }

    .hero {
        min-height: 0;
        padding: 20px 0 18px;
    }

    .courses-hero {
        max-width: calc(100vw - 28px);
        padding: 18px 0 8px;
        min-width: 0;
    }

    .courses-hero h1 {
        font-size: 36px;
    }

    .courses-hero .intro,
    .course-card strong,
    .course-card > span:last-child {
        min-width: 0;
        max-width: min(100%, 340px);
        display: block;
        overflow-wrap: anywhere;
    }

    .course-card > span:last-child {
        max-width: min(100%, 310px);
    }

    .course-grid {
        width: 100%;
        max-width: calc(100vw - 28px);
        min-width: 0;
    }

    .course-card {
        width: 100%;
        max-width: calc(100vw - 28px);
        min-width: 0;
        min-height: 190px;
        padding: 22px;
    }

    .course-card strong {
        font-size: 24px;
    }

    .course-card-icon {
        width: 34px;
        height: 28px;
    }

    .hero-art {
        display: none;
    }

    h1 {
        font-size: 38px;
    }

    .intro {
        font-size: 16px;
    }

    .quiz-type-strip {
        justify-content: flex-start;
    }

    .quiz-strip-title {
        width: 100%;
        justify-content: center;
        padding-right: 0;
    }

    .paper-section {
        padding: 0;
    }

    .section-heading {
        padding-left: 0;
        align-items: flex-start;
    }

    .paper-icon {
        width: 50px;
        height: 50px;
    }

    .section-heading p {
        font-size: 23px;
    }

    h2 {
        font-size: 22px;
        overflow-wrap: anywhere;
    }

    .topic-grid,
    .spec-grid,
    .resource-grid {
        grid-template-columns: 1fr;
    }

    .part-nav ol,
    .teaching-model,
    .check-columns {
        grid-template-columns: 1fr;
    }

    .lesson-header,
    .resource-panel,
    .lesson-part,
    .worksheet-part,
    .resource-summary {
        width: calc(100vw - 28px);
        max-width: calc(100vw - 28px);
        padding: 18px;
    }

    .lesson-header h2,
    .lesson-header p,
    .resource-panel,
    .lesson-part,
    .worksheet-part,
    .resource-summary {
        overflow-wrap: anywhere;
    }

    .lesson-header h2,
    .lesson-header p {
        max-width: calc(100vw - 64px);
    }

    .shift-line {
        grid-template-columns: 1fr;
    }

    .overflow-step-model,
    .shift-step-model {
        grid-template-columns: 1fr;
    }

    .topic-card {
        min-height: 0;
        padding: 24px 16px 18px;
    }

    .topic-card-header {
        align-items: flex-start;
        gap: 12px;
    }

    .topic-card h3,
    .topic-number {
        display: block;
        font-size: 25px;
        line-height: 1.14;
        overflow-wrap: anywhere;
    }

    .topic-number {
        margin: 0 0 2px;
    }

    .topic-list li {
        grid-template-columns: 1fr;
        align-items: start;
        gap: 12px;
        overflow: hidden;
    }

    .topic-actions {
        width: min(100%, 360px);
        max-width: 100%;
        display: grid;
        grid-template-columns: 1fr 1fr;
        justify-content: stretch;
    }

    .action-button {
        min-width: 0;
        width: 100%;
    }

    .quiz-timer-floating {
        right: 14px;
        bottom: 14px;
        width: min(172px, calc(100vw - 28px));
        min-width: 0;
        padding: 10px 12px;
    }

    .quiz-timer strong {
        font-size: 17px;
    }

    main:has(.lesson-header) {
        max-width: 390px;
        margin-left: 0;
        margin-right: 0;
    }

    main:has(.lesson-header) .lesson-header,
    main:has(.lesson-header) .resource-panel,
    main:has(.lesson-header) .lesson-part,
    main:has(.lesson-header) .worksheet-part,
    main:has(.lesson-header) .resource-summary {
        width: 100%;
        max-width: 100%;
    }

    .matching-grid label,
    .match-row {
        grid-template-columns: 1fr;
    }

    .quiz-question,
    .question-header,
    .quiz-form,
    .word-bank,
    .pseudocode-fill,
    .algorithm-code {
        max-width: 100%;
        min-width: 0;
    }

    .quiz-form {
        grid-template-columns: minmax(0, 1fr);
    }

    .quiz-question {
        overflow: hidden;
        padding: 18px;
    }

    .question-header {
        width: 100%;
        overflow: hidden;
    }

    .question-header h2,
    .question-header .section-note,
    .quiz-question h3 {
        white-space: normal;
        overflow-wrap: anywhere;
    }

    .question-header h2 {
        max-width: 18rem;
        line-height: 1.16;
    }

    .drag-word {
        max-width: 100%;
        white-space: normal;
        overflow-wrap: anywhere;
        text-align: center;
    }

    .word-bank {
        display: grid;
        grid-template-columns: minmax(0, 1fr);
        align-items: flex-start;
    }

    .word-bank .drag-word {
        width: 100%;
        max-width: 100%;
    }

    .pseudocode-fill p {
        min-width: max-content;
        white-space: nowrap;
    }

    .pseudocode-fill {
        width: 100%;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }

    .drop-blank,
    .match-drop {
        min-width: min(140px, 100%);
    }

    .gate-symbol-card {
        grid-template-columns: 1fr;
        justify-items: center;
    }

    .logic-figure-grid {
        grid-template-columns: 1fr;
    }

    .ide-layout {
        grid-template-columns: 1fr;
    }

    .ide-editor {
        border-right: 0;
        border-bottom: 1px solid var(--line);
    }

    footer {
        padding: 0;
    }
}