:root {
    --ink-950: #18201f;
    --ink-900: #223130;
    --ink-800: #355251;
    --ink-700: #4d6b6a;
    --ink-500: #7ca3a0;
    --ink-300: #c8d9d7;
    --paper-50: #f8f7f2;
    --paper-100: #f2eee4;
    --paper-200: #e3d8bf;
    --accent-gold: #d58b20;
    --accent-coral: #c95f44;
    --accent-leaf: #4f8a63;
    --accent-sky: #4372a7;
    --shadow-lg: 0 26px 80px rgba(24, 32, 31, 0.14);
    --shadow-md: 0 18px 50px rgba(24, 32, 31, 0.1);
    --radius-xl: 28px;
    --radius-lg: 18px;
    --radius-md: 14px;
    --ease-emph: cubic-bezier(0.2, 0.8, 0.2, 1);
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body,
p,
li,
td,
th,
small,
strong,
button,
label,
select {
    overflow-wrap: anywhere;
}

body {
    position: relative;
    margin: 0;
    min-height: 100vh;
    color: var(--ink-950);
    background:
        radial-gradient(circle at top left, rgba(213, 139, 32, 0.18), transparent 32%),
        radial-gradient(circle at 88% 12%, rgba(67, 114, 167, 0.18), transparent 26%),
        linear-gradient(160deg, #f8f7f2 0%, #f4efe5 46%, #ece5d7 100%);
    font-family: "Space Grotesk", sans-serif;
    overflow-x: hidden;
}

body.ds-teach-mode {
    overflow: hidden;
}

body.ds-teach-mode .ds-sidebar,
body.ds-teach-mode .ds-study-rail {
    display: none !important;
}

body.ds-teach-mode .ds-shell {
    grid-template-columns: 1fr;
    max-width: none;
}

body.ds-teach-mode .ds-topbar,
body.ds-teach-mode .ds-stage-card,
body.ds-teach-mode .ds-stage-header,
body.ds-teach-mode .ds-stage-footer,
body.ds-teach-mode .ds-visual-panel,
body.ds-teach-mode .ds-content-stack > *,
body.ds-teach-mode .ds-build-target.is-build-visible {
    animation: none !important;
}

body.ds-teach-mode .ds-stage-card,
body.ds-teach-mode .ds-topbar,
body.ds-teach-mode .ds-visual-panel,
body.ds-teach-mode .ds-content-stack > *,
body.ds-teach-mode .ds-build-target,
body.ds-teach-mode .ds-nav-button,
body.ds-teach-mode .ds-widget-button,
body.ds-teach-mode .ds-quiz-button,
body.ds-teach-mode .ds-pill,
body.ds-teach-mode .ds-build-chip {
    transition: none !important;
}

body.ds-teach-mode .ds-point-list li:hover,
body.ds-teach-mode .ds-mini-card:hover,
body.ds-teach-mode .ds-widget-button:hover,
body.ds-teach-mode .ds-nav-button:hover,
body.ds-teach-mode .ds-quiz-button:hover,
body.ds-teach-mode .ds-link-button:hover,
body.ds-teach-mode .ds-launch-link:hover,
body.ds-teach-mode .ds-lecture-link:hover {
    transform: none !important;
    box-shadow: none !important;
}

body.ds-teach-mode .ds-link-button::after,
body.ds-teach-mode .ds-launch-link::after {
    display: none !important;
}

body::before,
body::after {
    content: "";
    position: fixed;
    inset: auto;
    pointer-events: none;
    z-index: 0;
    filter: blur(22px);
    opacity: 0.58;
}

body::before {
    top: 6vh;
    right: -90px;
    width: 280px;
    height: 280px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(67, 114, 167, 0.18) 0%, rgba(67, 114, 167, 0) 72%);
    animation: dsFloat 15s ease-in-out infinite;
}

body::after {
    left: -120px;
    bottom: 4vh;
    width: 340px;
    height: 340px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(213, 139, 32, 0.18) 0%, rgba(213, 139, 32, 0) 74%);
    animation: dsFloat 19s ease-in-out infinite reverse;
}

a {
    color: inherit;
    text-decoration: none;
}

button,
input,
select {
    font: inherit;
}

.ds-app {
    min-height: 100vh;
    padding: 28px;
    position: relative;
    z-index: 1;
}

.ds-app.ds-app-teach {
    min-height: 100dvh;
    padding: 16px;
}

.ds-shell {
    max-width: 1480px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 300px minmax(0, 1fr);
    gap: 24px;
    align-items: start;
}

.ds-shell.ds-shell-teach {
    max-width: none;
    min-height: calc(100dvh - 32px);
    display: block;
}

.ds-sidebar {
    position: sticky;
    top: 28px;
    display: grid;
    align-content: start;
    gap: 14px;
    padding: 24px;
    border: 1px solid rgba(53, 82, 81, 0.12);
    border-radius: var(--radius-xl);
    background: rgba(248, 247, 242, 0.88);
    backdrop-filter: blur(22px);
    box-shadow: var(--shadow-md);
    animation: dsRiseIn 520ms var(--ease-emph) both;
}

.ds-course-kicker,
.ds-section-label,
.ds-slide-kicker {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-size: 0.8rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--accent-coral);
}

.ds-course-kicker::before,
.ds-section-label::before,
.ds-slide-kicker::before {
    content: "";
    width: 28px;
    height: 1px;
    background: currentColor;
}

.ds-sidebar h1,
.ds-home-hero h1,
.ds-stage-title,
.ds-study-slide h2 {
    margin: 10px 0 0;
    font-family: "Fraunces", serif;
    line-height: 1.05;
    font-weight: 700;
}

.ds-home-hero h1,
.ds-stage-title,
.ds-study-slide h2,
.ds-stage-lead,
.ds-home-subtitle,
.ds-rich-copy,
.ds-mini-card,
.ds-point-list li,
.ds-pill,
.ds-build-chip,
.ds-topic-picker,
.ds-quiz-button,
.ds-quiz-feedback,
.ds-eh-status,
.ds-contradiction-step p,
.ds-contradiction-tag,
.ds-rational-chip,
.ds-venn-legend {
    overflow-wrap: anywhere;
}

.ds-sidebar h1 {
    font-size: 2.2rem;
    margin: 0;
    line-height: 1.08;
    overflow-wrap: anywhere;
    hyphens: auto;
}

.ds-sidebar p {
    margin: 0;
    color: var(--ink-800);
    line-height: 1.6;
}

.ds-mode-switch {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 10px;
    margin: 4px 0 0;
}

.ds-mode-button,
.ds-nav-button,
.ds-link-button,
.ds-quiz-button,
.ds-launch-link {
    border: 0;
    border-radius: 999px;
    cursor: pointer;
    transition: transform 160ms ease, box-shadow 160ms ease, background 160ms ease, color 160ms ease, border-color 160ms ease;
}

.ds-mode-button {
    padding: 12px 16px;
    background: #e7dfcf;
    color: var(--ink-900);
    font-weight: 700;
}

.ds-mode-button.is-active {
    background: linear-gradient(135deg, var(--ink-950), var(--ink-800));
    color: white;
    box-shadow: 0 14px 32px rgba(24, 32, 31, 0.2);
    animation: dsActivePress 260ms var(--ease-emph);
}

.ds-mode-button:hover,
.ds-nav-button:hover,
.ds-link-button:hover,
.ds-quiz-button:hover,
.ds-launch-link:hover {
    transform: translateY(-1px);
}

.ds-meta-list,
.ds-lecture-list,
.ds-point-list,
.ds-link-list,
.ds-step-list,
.ds-chip-list {
    list-style: none;
    margin: 0;
    padding: 0;
}

.ds-meta-list {
    display: grid;
    gap: 10px;
    margin-top: 6px;
}

.ds-meta-list li {
    display: flex;
    gap: 10px;
    align-items: flex-start;
    color: var(--ink-900);
}

.ds-meta-list strong {
    min-width: 74px;
    color: var(--ink-700);
    font-size: 0.92rem;
}

.ds-lecture-list {
    display: grid;
    gap: 8px;
    margin-top: 6px;
    max-height: 50vh;
    overflow: auto;
    padding-right: 6px;
}

.ds-lecture-link {
    display: block;
    width: 100%;
    text-align: left;
    border: 1px solid rgba(53, 82, 81, 0.08);
    background: white;
    border-radius: var(--radius-md);
    padding: 14px 16px;
    color: var(--ink-900);
    overflow: hidden;
    transition: transform 180ms ease, box-shadow 180ms ease, background 180ms ease, border-color 180ms ease;
}

.ds-lecture-link.is-active {
    background: linear-gradient(135deg, rgba(213, 139, 32, 0.16), rgba(67, 114, 167, 0.12));
    border-color: rgba(201, 95, 68, 0.24);
}

.ds-lecture-link:hover {
    transform: translateX(4px);
    box-shadow: 0 12px 28px rgba(24, 32, 31, 0.08);
}

.ds-lecture-link strong {
    display: block;
    margin: 0;
    line-height: 1.3;
    overflow-wrap: anywhere;
}

.ds-lecture-link small {
    display: block;
    margin-top: 6px;
    color: var(--ink-700);
    line-height: 1.45;
    overflow-wrap: anywhere;
}

.ds-main {
    display: grid;
    gap: 24px;
}

.ds-main.ds-main-teach {
    min-height: calc(100dvh - 32px);
    grid-template-rows: auto minmax(0, 1fr);
    gap: 10px;
}

.ds-topbar,
.ds-study-topbar,
.ds-home-topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
    padding: 18px 22px;
    border: 1px solid rgba(53, 82, 81, 0.12);
    border-radius: var(--radius-xl);
    background: rgba(248, 247, 242, 0.88);
    backdrop-filter: blur(22px);
    box-shadow: var(--shadow-md);
    animation: dsRiseIn 560ms var(--ease-emph) both;
}

.ds-topbar-left,
.ds-topbar-right {
    display: flex;
    gap: 14px;
    align-items: center;
    flex-wrap: wrap;
}

.ds-pill {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-radius: 999px;
    background: rgba(77, 107, 106, 0.08);
    color: var(--ink-800);
    font-size: 0.9rem;
    font-weight: 600;
}

.ds-topic-picker {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 10px;
    border-radius: 999px;
    background: rgba(77, 107, 106, 0.08);
    color: var(--ink-800);
}

.ds-topic-label {
    font-size: 0.82rem;
    font-weight: 700;
    letter-spacing: 0.04em;
    text-transform: uppercase;
    color: var(--ink-700);
}

.ds-topic-select {
    min-width: 220px;
    border: 0;
    background: transparent;
    color: var(--ink-950);
    font-weight: 700;
    padding: 2px 4px;
    outline: none;
    cursor: pointer;
}

.ds-topic-select option {
    color: var(--ink-950);
}

mjx-container {
    max-width: 100%;
}

mjx-container[display="true"] {
    display: block;
    overflow-x: auto;
    overflow-y: hidden;
    -webkit-overflow-scrolling: touch;
    padding-bottom: 2px;
}

.ds-link-button,
.ds-launch-link {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 11px 18px;
    background: linear-gradient(135deg, var(--accent-coral), var(--accent-gold));
    color: white;
    font-weight: 700;
    box-shadow: 0 14px 30px rgba(201, 95, 68, 0.22);
    position: relative;
    overflow: hidden;
}

.ds-link-button::after,
.ds-launch-link::after {
    content: "";
    position: absolute;
    inset: 0;
    background: linear-gradient(115deg, transparent 18%, rgba(255, 255, 255, 0.32) 48%, transparent 74%);
    transform: translateX(-140%);
    transition: transform 420ms var(--ease-emph);
}

.ds-link-button:hover::after,
.ds-launch-link:hover::after {
    transform: translateX(140%);
}

.ds-stage-card,
.ds-study-slide,
.ds-home-hero,
.ds-home-card {
    border: 1px solid rgba(53, 82, 81, 0.12);
    border-radius: var(--radius-xl);
    background: rgba(252, 251, 247, 0.95);
    box-shadow: var(--shadow-lg);
}

.ds-stage-card {
    min-height: calc(100vh - 180px);
    display: grid;
    grid-template-rows: auto 1fr auto;
    overflow: hidden;
    position: relative;
    animation: dsStageEnter 520ms var(--ease-emph) both;
}

.ds-main.ds-main-teach .ds-stage-card {
    min-height: 0;
    height: 100%;
}

.ds-stage-card::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    height: 4px;
    width: var(--slide-progress, 12%);
    background: linear-gradient(90deg, var(--accent-coral), var(--accent-gold), var(--accent-sky));
    box-shadow: 0 0 22px rgba(201, 95, 68, 0.24);
    transition: width 280ms var(--ease-emph);
}

.ds-stage-header {
    padding: 34px 34px 12px;
    animation: dsRiseIn 580ms var(--ease-emph) both;
}

.ds-main.ds-main-teach .ds-stage-header {
    padding: 24px 28px 8px;
}

.ds-stage-title {
    font-size: clamp(2.3rem, 4vw, 4.2rem);
}

.ds-main.ds-main-teach .ds-stage-title {
    font-size: clamp(1.9rem, 3vw, 3.2rem);
}

.ds-stage-lead,
.ds-study-slide .ds-stage-lead {
    margin: 16px 0 0;
    max-width: 68ch;
    font-size: 1.06rem;
    line-height: 1.7;
    color: var(--ink-800);
}

.ds-main.ds-main-teach .ds-stage-lead {
    margin-top: 10px;
    max-width: 76ch;
    font-size: 0.98rem;
    line-height: 1.55;
}

.ds-stage-body {
    padding: 12px 34px 28px;
    display: grid;
    grid-template-columns: minmax(0, 1.18fr) minmax(300px, 0.82fr);
    gap: 28px;
    align-items: start;
}

.ds-main.ds-main-teach .ds-stage-body {
    min-height: 0;
    padding: 10px 28px 18px;
    gap: 18px;
    align-items: stretch;
    overflow: hidden;
}

.ds-stage-body.is-single {
    grid-template-columns: minmax(0, 1fr);
}

.ds-content-stack {
    display: grid;
    gap: 18px;
}

.ds-main.ds-main-teach .ds-content-stack,
.ds-main.ds-main-teach .ds-visual-panel {
    min-height: 0;
    overflow: auto;
    padding-right: 8px;
}

.ds-main.ds-main-teach .ds-content-stack {
    gap: 14px;
}

.ds-main.ds-main-teach .ds-topbar {
    padding: 12px 16px;
    border-radius: 20px;
}

.ds-main.ds-main-teach .ds-topbar-left {
    gap: 10px;
}

.ds-main.ds-main-teach .ds-pill,
.ds-main.ds-main-teach .ds-build-chip {
    padding: 6px 10px;
    font-size: 0.82rem;
}

.ds-main.ds-main-teach .ds-topic-picker {
    padding: 5px 10px;
}

.ds-main.ds-main-teach .ds-topic-label {
    font-size: 0.74rem;
}

.ds-main.ds-main-teach .ds-topic-select {
    min-width: 180px;
    font-size: 0.88rem;
}

.ds-main.ds-main-teach .ds-progress {
    width: min(220px, 28vw);
    height: 8px;
}

.ds-content-stack > * {
    opacity: 0;
    transform: translateY(14px);
    animation: dsRiseIn 520ms var(--ease-emph) forwards;
}

.ds-content-stack > *:nth-child(1) {
    animation-delay: 60ms;
}

.ds-content-stack > *:nth-child(2) {
    animation-delay: 120ms;
}

.ds-content-stack > *:nth-child(3) {
    animation-delay: 180ms;
}

.ds-content-stack > *:nth-child(4) {
    animation-delay: 240ms;
}

.ds-content-stack > *:nth-child(5) {
    animation-delay: 300ms;
}

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

.ds-point-list li {
    padding: 14px 16px;
    border-radius: var(--radius-md);
    background: linear-gradient(135deg, rgba(67, 114, 167, 0.08), rgba(213, 139, 32, 0.08));
    color: var(--ink-900);
    line-height: 1.55;
    border: 1px solid rgba(77, 107, 106, 0.08);
    transition: transform 180ms ease, box-shadow 180ms ease, border-color 180ms ease;
}

.ds-main.ds-main-teach .ds-point-list li,
.ds-main.ds-main-teach .ds-proof-box,
.ds-main.ds-main-teach .ds-note-box,
.ds-main.ds-main-teach .ds-table-box,
.ds-main.ds-main-teach .ds-grid-box,
.ds-main.ds-main-teach .ds-exercise-box,
.ds-main.ds-main-teach .ds-summary-box,
.ds-main.ds-main-teach .ds-quiz-box,
.ds-main.ds-main-teach .ds-svg-panel,
.ds-main.ds-main-teach .ds-mini-card,
.ds-main.ds-main-teach .ds-widget-card {
    padding: 14px 16px;
}

.ds-main.ds-main-teach .ds-widget-card {
    min-height: 100%;
}

.ds-main.ds-main-teach .ds-rich-copy,
.ds-main.ds-main-teach .ds-point-list li,
.ds-main.ds-main-teach .ds-mini-card,
.ds-main.ds-main-teach .ds-table-box table,
.ds-main.ds-main-teach .ds-quiz-box {
    font-size: 0.94rem;
    line-height: 1.45;
}

.ds-main.ds-main-teach .ds-grid-2,
.ds-main.ds-main-teach .ds-grid-3,
.ds-main.ds-main-teach .ds-card-grid,
.ds-main.ds-main-teach .ds-step-list,
.ds-main.ds-main-teach .ds-point-list {
    gap: 10px;
}

.ds-point-list li:hover {
    transform: translateY(-2px);
    box-shadow: 0 14px 26px rgba(24, 32, 31, 0.06);
    border-color: rgba(67, 114, 167, 0.18);
}

.ds-rich-copy {
    color: var(--ink-900);
    line-height: 1.7;
}

.ds-rich-copy p,
.ds-rich-copy ul,
.ds-rich-copy ol {
    margin: 0;
}

.ds-rich-copy ul,
.ds-rich-copy ol {
    padding-left: 20px;
}

.ds-rich-copy > * + * {
    margin-top: 14px;
}

.ds-visual-panel {
    padding: 22px;
    border-radius: calc(var(--radius-xl) - 8px);
    background:
        radial-gradient(circle at top left, rgba(213, 139, 32, 0.12), transparent 38%),
        linear-gradient(160deg, #fffdf7, #f5f1e7);
    border: 1px solid rgba(77, 107, 106, 0.12);
    min-height: 280px;
    animation: dsVisualIn 620ms var(--ease-emph) both 140ms;
}

.ds-main.ds-main-teach .ds-visual-panel {
    min-height: 0;
    padding: 16px;
}

.ds-visual-panel svg,
.ds-svg-panel svg {
    width: 100%;
    height: auto;
}

.ds-svg-panel,
.ds-proof-box,
.ds-note-box,
.ds-table-box,
.ds-grid-box,
.ds-exercise-box,
.ds-quiz-box,
.ds-summary-box {
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: white;
}

.ds-svg-panel {
    padding: 18px;
    background: linear-gradient(180deg, #fdfcf8, #f4efe5);
}

.ds-proof-box,
.ds-note-box,
.ds-table-box,
.ds-grid-box,
.ds-exercise-box,
.ds-summary-box {
    padding: 18px 20px;
}

.ds-proof-box {
    background: linear-gradient(180deg, rgba(79, 138, 99, 0.08), rgba(79, 138, 99, 0.02));
}

.ds-note-box {
    background: linear-gradient(180deg, rgba(201, 95, 68, 0.08), rgba(213, 139, 32, 0.04));
}

.ds-table-box {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.ds-table-box table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.95rem;
}

.ds-table-box th,
.ds-table-box td {
    padding: 10px 12px;
    border-bottom: 1px solid rgba(77, 107, 106, 0.12);
    text-align: left;
    vertical-align: top;
}

.ds-table-box th {
    color: var(--ink-700);
    font-size: 0.82rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.ds-grid-2,
.ds-grid-3,
.ds-card-grid {
    display: grid;
    gap: 16px;
}

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

.ds-grid-3 {
    grid-template-columns: repeat(3, minmax(0, 1fr));
}

.ds-card-grid {
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.ds-mini-card {
    padding: 16px;
    border-radius: var(--radius-md);
    background: linear-gradient(180deg, #fffdf9, #f7f2e8);
    border: 1px solid rgba(77, 107, 106, 0.12);
    transition: transform 180ms ease, box-shadow 180ms ease, border-color 180ms ease;
}

.ds-mini-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 16px 32px rgba(24, 32, 31, 0.08);
    border-color: rgba(201, 95, 68, 0.18);
}

.ds-mini-card strong {
    display: block;
    margin-bottom: 8px;
    color: var(--ink-950);
}

.ds-formula {
    margin: 0;
    padding: 14px 18px;
    border-radius: var(--radius-md);
    background: #f6f1e7;
    color: var(--ink-950);
    text-align: center;
    font-size: 1.08rem;
}

.ds-chip-list {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.ds-chip {
    display: inline-flex;
    align-items: center;
    padding: 8px 12px;
    border-radius: 999px;
    background: rgba(67, 114, 167, 0.1);
    color: var(--ink-900);
    font-weight: 700;
    font-size: 0.9rem;
}

.ds-step-list {
    display: grid;
    gap: 12px;
}

.ds-step-list li {
    display: grid;
    grid-template-columns: 34px minmax(0, 1fr);
    gap: 14px;
    align-items: start;
}

.ds-step-list span {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 34px;
    height: 34px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-coral), var(--accent-gold));
    color: white;
    font-weight: 700;
}

.ds-stage-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
    padding: 20px 34px 30px;
    border-top: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, rgba(248, 247, 242, 0.45), rgba(248, 247, 242, 0.95));
    animation: dsRiseIn 640ms var(--ease-emph) both 90ms;
}

.ds-main.ds-main-teach .ds-stage-footer {
    padding: 10px 20px 14px;
}

.ds-main.ds-main-teach .ds-nav-button {
    min-width: 106px;
    padding: 11px 16px;
}

.ds-build-chip {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-radius: 999px;
    background: rgba(201, 95, 68, 0.1);
    color: var(--ink-900);
    font-size: 0.9rem;
    font-weight: 700;
}

.ds-build-chip::before {
    content: "";
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent-coral), var(--accent-gold));
    box-shadow: 0 0 12px rgba(201, 95, 68, 0.35);
}

.ds-stage-card.is-build-mode .ds-content-stack > *,
.ds-stage-card.is-build-mode .ds-point-list li,
.ds-stage-card.is-build-mode .ds-rich-copy > *,
.ds-stage-card.is-build-mode .ds-visual-panel > * {
    opacity: 1;
    transform: none;
    animation: none;
}

.ds-build-target.is-build-visible {
    animation: dsBuildIn 420ms var(--ease-emph) both;
}

.ds-build-target.is-build-hidden {
    visibility: hidden;
    opacity: 0 !important;
    pointer-events: none;
}

.ds-nav-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    padding: 13px 20px;
    background: var(--ink-950);
    color: white;
    font-weight: 700;
    min-width: 122px;
}

.ds-nav-button:not([disabled]):active,
.ds-link-button:active,
.ds-launch-link:active,
.ds-mode-button:active,
.ds-quiz-button:active {
    transform: translateY(1px) scale(0.99);
}

.ds-nav-button[disabled] {
    background: #c7cbc7;
    color: #657372;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

.ds-count {
    font-weight: 700;
    color: var(--ink-800);
}

.ds-study-layout {
    display: grid;
    gap: 22px;
}

.ds-study-grid {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 280px;
    gap: 24px;
}

.ds-study-stack {
    display: grid;
    gap: 24px;
}

.ds-study-slide {
    padding: 30px 32px;
    animation: dsRiseIn 560ms var(--ease-emph) both;
}

.ds-study-slide h2 {
    font-size: clamp(2rem, 3vw, 3rem);
}

.ds-study-rail {
    position: sticky;
    top: 28px;
    height: fit-content;
    padding: 22px;
    border: 1px solid rgba(53, 82, 81, 0.12);
    border-radius: var(--radius-xl);
    background: rgba(248, 247, 242, 0.88);
    box-shadow: var(--shadow-md);
    animation: dsRiseIn 620ms var(--ease-emph) both;
}

.ds-study-rail h3 {
    margin: 0 0 12px;
    font-size: 1rem;
    color: var(--ink-700);
    text-transform: uppercase;
    letter-spacing: 0.12em;
}

.ds-study-rail a {
    display: block;
    padding: 10px 12px;
    border-radius: 12px;
    color: var(--ink-900);
}

.ds-study-rail a:hover {
    background: rgba(67, 114, 167, 0.08);
}

.ds-home-layout {
    max-width: 1380px;
    margin: 0 auto;
    display: grid;
    gap: 24px;
}

.ds-home-hero {
    padding: 42px;
    background:
        radial-gradient(circle at top right, rgba(67, 114, 167, 0.14), transparent 28%),
        linear-gradient(135deg, rgba(252, 251, 247, 0.96), rgba(245, 239, 229, 0.96));
    animation: dsRiseIn 560ms var(--ease-emph) both;
}

.ds-home-hero h1 {
    font-size: clamp(2.8rem, 5vw, 5rem);
}

.ds-home-subtitle {
    max-width: 70ch;
    margin-top: 18px;
    font-size: 1.08rem;
    line-height: 1.75;
    color: var(--ink-800);
}

.ds-home-stats {
    display: flex;
    gap: 14px;
    flex-wrap: wrap;
    margin-top: 24px;
}

.ds-home-card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 22px;
}

.ds-home-card {
    padding: 28px;
    display: grid;
    gap: 16px;
    animation: dsRiseIn 520ms var(--ease-emph) both;
    animation-delay: calc(var(--stagger, 0) * 60ms);
}

.ds-home-card h2 {
    margin: 0;
    font-size: 1.5rem;
    font-family: "Fraunces", serif;
}

.ds-home-card p {
    margin: 0;
    color: var(--ink-800);
    line-height: 1.65;
}

.ds-home-actions {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-top: 4px;
}

.ds-home-actions .ds-launch-link.is-secondary {
    background: white;
    color: var(--ink-950);
    border: 1px solid rgba(77, 107, 106, 0.16);
    box-shadow: none;
}

.ds-quiz-box {
    margin-top: 18px;
    padding: 18px 20px;
    display: grid;
    gap: 14px;
    background: linear-gradient(180deg, rgba(67, 114, 167, 0.08), rgba(67, 114, 167, 0.02));
    position: relative;
    overflow: hidden;
}

.ds-quiz-box::before {
    content: "";
    position: absolute;
    inset: 0 auto 0 0;
    width: 4px;
    background: linear-gradient(180deg, var(--accent-sky), var(--accent-coral));
}

.ds-quiz-options {
    display: grid;
    gap: 10px;
}

.ds-quiz-button {
    width: 100%;
    padding: 13px 14px;
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: white;
    text-align: left;
    color: var(--ink-900);
    position: relative;
    overflow: hidden;
}

.ds-quiz-button.is-correct {
    background: rgba(79, 138, 99, 0.12);
    border-color: rgba(79, 138, 99, 0.34);
}

.ds-quiz-button.is-incorrect {
    background: rgba(201, 95, 68, 0.12);
    border-color: rgba(201, 95, 68, 0.34);
}

.ds-quiz-feedback {
    display: none;
    padding: 12px 14px;
    border-radius: 12px;
    background: rgba(24, 32, 31, 0.06);
    color: var(--ink-900);
    line-height: 1.55;
}

.ds-quiz-feedback.is-visible {
    display: block;
    animation: dsFeedbackIn 260ms var(--ease-emph) both;
}

.ds-embed {
    width: 100%;
    border: 0;
    border-radius: 16px;
    background: white;
    min-height: 360px;
    box-shadow: 0 18px 40px rgba(24, 32, 31, 0.08);
}

.ds-footer-links {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
}

.ds-mono {
    font-family: "IBM Plex Mono", monospace;
}

.ds-key-row {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.ds-key {
    padding: 6px 10px;
    border-radius: 10px;
    background: white;
    border: 1px solid rgba(77, 107, 106, 0.12);
    font-family: "IBM Plex Mono", monospace;
    font-size: 0.85rem;
}

.ds-widget-card {
    padding: 18px;
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, #fffdf9, #f2ede2);
    box-shadow: 0 18px 40px rgba(24, 32, 31, 0.08);
}

.ds-widget-head {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 12px;
}

.ds-widget-head strong {
    font-size: 1rem;
}

.ds-widget-controls {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.ds-widget-button {
    border: 1px solid rgba(77, 107, 106, 0.14);
    background: white;
    color: var(--ink-900);
    padding: 9px 12px;
    border-radius: 999px;
    font-weight: 700;
    cursor: pointer;
    transition: transform 160ms ease, box-shadow 160ms ease, background 160ms ease;
}

.ds-widget-button:hover {
    transform: translateY(-1px);
    box-shadow: 0 10px 24px rgba(24, 32, 31, 0.08);
}

.ds-widget-button.is-primary {
    background: linear-gradient(135deg, var(--accent-coral), var(--accent-gold));
    color: white;
    border-color: transparent;
}

.ds-widget-meta {
    display: flex;
    gap: 14px;
    flex-wrap: wrap;
    color: var(--ink-800);
    font-size: 0.92rem;
    margin-bottom: 12px;
}

.ds-hanoi-board {
    position: relative;
    height: 290px;
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background:
        radial-gradient(circle at top center, rgba(67, 114, 167, 0.08), transparent 34%),
        linear-gradient(180deg, #fdfaf2, #ede4d2);
    overflow: hidden;
}

.ds-hanoi-base {
    position: absolute;
    left: 8%;
    right: 8%;
    bottom: 28px;
    height: 12px;
    border-radius: 999px;
    background: linear-gradient(90deg, #4d6b6a, #223130);
}

.ds-hanoi-peg {
    position: absolute;
    bottom: 40px;
    width: 12px;
    height: 176px;
    margin-left: -6px;
    border-radius: 999px;
    background: linear-gradient(180deg, #7ca3a0, #355251);
    box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.18);
}

.ds-hanoi-peg-label {
    position: absolute;
    bottom: 8px;
    transform: translateX(-50%);
    font-family: "IBM Plex Mono", monospace;
    font-size: 0.85rem;
    color: var(--ink-700);
}

.ds-hanoi-disk {
    position: absolute;
    height: 22px;
    border-radius: 999px;
    left: 0;
    bottom: 0;
    transform: translateX(-50%);
    transition:
        left 480ms cubic-bezier(0.2, 0.8, 0.2, 1),
        bottom 480ms cubic-bezier(0.2, 0.8, 0.2, 1),
        width 480ms cubic-bezier(0.2, 0.8, 0.2, 1);
    box-shadow:
        inset 0 -4px 10px rgba(24, 32, 31, 0.18),
        0 10px 18px rgba(24, 32, 31, 0.12);
    border: 1px solid rgba(24, 32, 31, 0.08);
}

.ds-hanoi-disk span {
    position: absolute;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 700;
    color: rgba(24, 32, 31, 0.8);
}

.ds-hanoi-caption {
    margin-top: 12px;
    color: var(--ink-800);
    line-height: 1.6;
}

.ds-domino-row {
    display: flex;
    align-items: end;
    gap: 10px;
    min-height: 210px;
    padding: 12px 8px 0;
}

.ds-domino {
    width: 28px;
    height: 140px;
    border-radius: 10px;
    background: linear-gradient(180deg, #fffef8, #e8dcc4);
    border: 1px solid rgba(24, 32, 31, 0.14);
    box-shadow: 0 12px 24px rgba(24, 32, 31, 0.08);
    transform-origin: bottom left;
    transition: transform 420ms cubic-bezier(0.2, 0.8, 0.2, 1), background 220ms ease;
    position: relative;
}

.ds-domino::before,
.ds-domino::after {
    content: "";
    position: absolute;
    left: 50%;
    width: 8px;
    height: 8px;
    margin-left: -4px;
    border-radius: 50%;
    background: rgba(24, 32, 31, 0.7);
}

.ds-domino::before {
    top: 28px;
}

.ds-domino::after {
    bottom: 28px;
}

.ds-domino.is-fallen {
    transform: rotate(74deg) translate(20px, 8px);
    background: linear-gradient(180deg, #f7c35f, #e98b5e);
}

.ds-domino-index {
    position: absolute;
    bottom: -24px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 0.75rem;
    color: var(--ink-700);
}

.ds-tree-board {
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, #fcfaf3, #efe7d8);
    padding: 12px;
}

.ds-tree-board.is-compact {
    padding: 8px;
}

.ds-tree-board svg {
    width: 100%;
    height: auto;
    display: block;
}

.ds-widget-card.is-compact .ds-widget-head {
    margin-bottom: 8px;
}

.ds-widget-card.is-compact .ds-widget-head strong {
    font-size: 0.94rem;
}

.ds-widget-card.is-compact .ds-widget-controls {
    gap: 6px;
}

.ds-widget-card.is-compact .ds-widget-button {
    padding: 7px 10px;
    font-size: 0.84rem;
}

.ds-widget-meta.is-compact {
    gap: 8px;
    margin-bottom: 8px;
    font-size: 0.84rem;
}

.ds-tree-edge,
.ds-tree-node {
    opacity: 0.16;
    transition: opacity 220ms ease, transform 220ms ease, filter 220ms ease;
}

.ds-tree-edge.is-visible,
.ds-tree-node.is-visible {
    opacity: 1;
}

.ds-tree-node circle {
    filter: drop-shadow(0 10px 18px rgba(24, 32, 31, 0.12));
}

.ds-tree-node.is-visible circle {
    animation: dsNodePop 320ms var(--ease-emph);
}

.ds-venn-board {
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, #fdfbf4, #ede4d2);
    padding: 12px;
}

.ds-venn-board svg {
    width: 100%;
    display: block;
}

.ds-venn-region {
    opacity: 0.08;
    transition: opacity 260ms ease, fill 260ms ease;
}

.ds-venn-region.is-active {
    opacity: 0.94;
}

.ds-venn-legend {
    margin-top: 10px;
    color: var(--ink-800);
    line-height: 1.55;
}

.ds-traversal-board {
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, #fbfaf4, #ede4d2);
    padding: 12px;
}

.ds-traversal-board svg {
    width: 100%;
    display: block;
}

.ds-graph-edge {
    stroke: rgba(53, 82, 81, 0.34);
    stroke-width: 4;
    transition: stroke 240ms ease, stroke-width 240ms ease, opacity 240ms ease;
}

.ds-graph-edge.is-active {
    stroke: #c95f44;
    stroke-width: 6;
}

.ds-graph-node circle {
    fill: #f7f1e2;
    stroke: rgba(53, 82, 81, 0.46);
    stroke-width: 2.5;
    transition: fill 240ms ease, stroke 240ms ease, transform 240ms ease;
}

.ds-graph-node text {
    fill: var(--ink-900);
    font-weight: 700;
    font-size: 14px;
}

.ds-graph-node.is-queued circle {
    fill: #dce7f4;
    stroke: #4372a7;
}

.ds-graph-node.is-visited circle {
    fill: #f7c35f;
    stroke: #c95f44;
    transform: scale(1.08);
}

.ds-graph-node.is-current circle {
    fill: #8bc28a;
    stroke: #4f8a63;
    transform: scale(1.14);
}

.ds-proof-board,
.ds-diagonal-board,
.ds-partition-board,
.ds-span-board {
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, #fcfaf3, #ede4d2);
    padding: 12px;
}

.ds-proof-steps {
    display: grid;
    gap: 10px;
}

.ds-proof-step {
    padding: 12px 14px;
    border-radius: 14px;
    border: 1px solid rgba(77, 107, 106, 0.1);
    background: white;
    opacity: 0.22;
    transform: translateX(0);
    transition: opacity 220ms ease, transform 220ms ease, border-color 220ms ease;
}

.ds-proof-step.is-visible {
    opacity: 1;
    border-color: rgba(67, 114, 167, 0.18);
    transform: translateX(6px);
}

.ds-proof-step strong {
    display: block;
    margin-bottom: 4px;
}

.ds-diagonal-board svg,
.ds-span-board svg {
    width: 100%;
    display: block;
}

.ds-diagonal-cell {
    transition: fill 220ms ease, stroke 220ms ease;
}

.ds-diagonal-cell.is-highlight {
    fill: #f7c35f;
    stroke: #c95f44;
    stroke-width: 2;
}

.ds-diagonal-answer {
    margin-top: 10px;
    font-family: "IBM Plex Mono", monospace;
    font-size: 1.02rem;
    color: var(--ink-900);
}

.ds-rational-board,
.ds-transitivity-board,
.ds-contradiction-board {
    border-radius: var(--radius-lg);
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: linear-gradient(180deg, #fcfaf3, #ede4d2);
    padding: 12px;
}

.ds-rational-board svg,
.ds-transitivity-board svg {
    width: 100%;
    display: block;
}

.ds-rational-sweep {
    fill: none;
    stroke: rgba(201, 95, 68, 0.38);
    stroke-width: 5;
    stroke-linecap: round;
    stroke-linejoin: round;
    marker-end: url(#ds-rational-arrow);
}

.ds-rational-cell rect {
    fill: rgba(255, 255, 255, 0.72);
    stroke: rgba(77, 107, 106, 0.18);
    stroke-width: 1.2;
    transition: fill 220ms ease, stroke 220ms ease, transform 220ms ease, opacity 220ms ease;
}

.ds-rational-cell text {
    fill: var(--ink-900);
}

.ds-rational-cell.is-visited rect {
    fill: rgba(220, 231, 244, 0.72);
}

.ds-rational-cell.is-accepted rect {
    fill: rgba(139, 194, 138, 0.28);
    stroke: rgba(79, 138, 99, 0.56);
}

.ds-rational-cell.is-skipped rect {
    fill: rgba(201, 95, 68, 0.12);
    stroke: rgba(201, 95, 68, 0.24);
}

.ds-rational-cell.is-current rect {
    fill: #f7c35f;
    stroke: #c95f44;
    stroke-width: 2.4;
    transform: scale(1.06);
}

.ds-rational-marker {
    fill: #c95f44;
    opacity: 0;
    transform-origin: center;
    transition: opacity 160ms ease;
}

.ds-rational-marker.is-visible {
    opacity: 1;
    animation: dsPulseSoft 900ms ease-in-out infinite;
}

.ds-rational-enumeration {
    margin-top: 12px;
    display: grid;
    gap: 10px;
}

.ds-rational-list {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.ds-rational-chip {
    display: inline-flex;
    align-items: center;
    padding: 8px 10px;
    border-radius: 999px;
    background: white;
    border: 1px solid rgba(77, 107, 106, 0.12);
    font-family: "IBM Plex Mono", monospace;
    font-size: 0.8rem;
    color: var(--ink-900);
}

.ds-rational-chip.is-empty {
    color: var(--ink-700);
}

.ds-partition-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 12px;
}

.ds-partition-class {
    min-height: 160px;
    border-radius: 16px;
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: rgba(255, 255, 255, 0.72);
    padding: 12px;
}

.ds-partition-class h4 {
    margin: 0 0 10px;
    font-size: 0.95rem;
}

.ds-partition-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.ds-partition-chip {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 34px;
    padding: 8px 10px;
    border-radius: 999px;
    background: #fff;
    border: 1px solid rgba(77, 107, 106, 0.12);
    color: var(--ink-900);
    font-family: "IBM Plex Mono", monospace;
    opacity: 0.2;
    transform: translateY(8px) scale(0.96);
    transition: opacity 240ms ease, transform 240ms ease, background 240ms ease, border-color 240ms ease;
}

.ds-partition-chip.is-visible {
    opacity: 1;
    transform: translateY(0) scale(1);
    background: linear-gradient(180deg, #fffef9, #f7efd8);
    border-color: rgba(201, 95, 68, 0.18);
}

.ds-transitivity-edge {
    opacity: 0.12;
    stroke-width: 4;
    transition: opacity 220ms ease, stroke 220ms ease, stroke-width 220ms ease, stroke-dasharray 220ms ease;
}

.ds-transitivity-edge.is-base {
    stroke: rgba(53, 82, 81, 0.56);
}

.ds-transitivity-edge.is-shortcut {
    stroke: rgba(201, 95, 68, 0.78);
    stroke-dasharray: 8 8;
}

.ds-transitivity-edge.is-visible {
    opacity: 1;
}

.ds-transitivity-edge.is-highlight {
    stroke-width: 6;
}

.ds-transitivity-edge.is-new {
    animation: dsLineFlash 680ms ease;
}

.ds-transitivity-node circle {
    fill: #f7f1e2;
    stroke: rgba(53, 82, 81, 0.42);
    stroke-width: 2.5;
    transition: fill 220ms ease, stroke 220ms ease, transform 220ms ease;
}

.ds-transitivity-node text {
    fill: var(--ink-900);
    font-size: 15px;
    font-weight: 700;
}

.ds-transitivity-node.is-active circle {
    fill: #dce7f4;
    stroke: #4372a7;
    transform: scale(1.12);
}

.ds-transitivity-caption {
    margin-top: 12px;
    min-height: 2.6em;
    line-height: 1.55;
    color: var(--ink-900);
}

.ds-span-edge,
.ds-span-node {
    transition: opacity 220ms ease, stroke 220ms ease, stroke-width 220ms ease, transform 220ms ease;
}

.ds-span-edge {
    opacity: 0.25;
    stroke: rgba(53, 82, 81, 0.34);
    stroke-width: 4;
}

.ds-span-edge.is-tree {
    opacity: 1;
    stroke: #c95f44;
    stroke-width: 6;
}

.ds-span-node circle {
    fill: #f7f1e2;
    stroke: rgba(53, 82, 81, 0.42);
    stroke-width: 2.5;
}

.ds-span-node text {
    fill: var(--ink-900);
    font-weight: 700;
    font-size: 14px;
}

.ds-span-node.is-included circle {
    fill: #8bc28a;
    stroke: #4f8a63;
    transform: scale(1.12);
}

.ds-euler-hamilton-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 14px;
}

.ds-eh-panel {
    border-radius: 18px;
    border: 1px solid rgba(77, 107, 106, 0.12);
    background: rgba(255, 255, 255, 0.52);
    padding: 12px;
}

.ds-eh-panel header {
    display: grid;
    gap: 4px;
    margin-bottom: 10px;
}

.ds-eh-panel header span {
    color: var(--ink-700);
    font-size: 0.9rem;
}

.ds-eh-board {
    border-radius: 14px;
    background: linear-gradient(180deg, #fffdf9, #f4ecdb);
    padding: 10px;
}

.ds-eh-board svg {
    width: 100%;
    display: block;
}

.ds-eh-edge {
    stroke: rgba(53, 82, 81, 0.34);
    stroke-width: 4;
    transition: stroke 220ms ease, stroke-width 220ms ease, opacity 220ms ease;
}

.ds-eh-edge.is-visited {
    stroke: rgba(67, 114, 167, 0.82);
}

.ds-eh-edge.is-active {
    stroke: #c95f44;
    stroke-width: 6;
}

.ds-eh-node circle {
    fill: #f7f1e2;
    stroke: rgba(53, 82, 81, 0.42);
    stroke-width: 2.5;
    transition: fill 220ms ease, stroke 220ms ease, transform 220ms ease;
}

.ds-eh-node text {
    fill: var(--ink-900);
    font-size: 14px;
    font-weight: 700;
}

.ds-eh-node.is-visited circle {
    fill: rgba(139, 194, 138, 0.24);
    stroke: #4f8a63;
}

.ds-eh-node.is-current circle {
    fill: #f7c35f;
    stroke: #c95f44;
    transform: scale(1.12);
}

.ds-eh-token {
    fill: #c95f44;
    opacity: 0.88;
    transition: cx 360ms ease, cy 360ms ease, opacity 220ms ease;
}

.ds-eh-token.is-visible {
    animation: dsPulseSoft 900ms ease-in-out infinite;
}

.ds-eh-status {
    margin-top: 10px;
    font-size: 0.92rem;
    color: var(--ink-800);
    line-height: 1.55;
}

.ds-contradiction-claim {
    display: grid;
    gap: 12px;
    margin-bottom: 14px;
}

.ds-contradiction-board.is-compact .ds-contradiction-claim {
    gap: 8px;
    margin-bottom: 10px;
}

.ds-contradiction-fraction {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    align-self: start;
    padding: 12px 16px;
    border-radius: 16px;
    background: rgba(255, 255, 255, 0.74);
    border: 1px solid rgba(77, 107, 106, 0.12);
    font-size: 1.15rem;
    font-weight: 700;
}

.ds-contradiction-board.is-compact .ds-contradiction-fraction {
    padding: 10px 14px;
    font-size: 1rem;
}

.ds-contradiction-fraction span {
    font-family: "IBM Plex Mono", monospace;
}

.ds-contradiction-tags {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.ds-contradiction-board.is-compact .ds-contradiction-tags {
    gap: 6px;
}

.ds-contradiction-tag {
    display: inline-flex;
    align-items: center;
    padding: 8px 12px;
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.64);
    border: 1px solid rgba(77, 107, 106, 0.12);
    color: var(--ink-800);
    transition: background 220ms ease, border-color 220ms ease, transform 220ms ease;
}

.ds-contradiction-board.is-compact .ds-contradiction-tag {
    padding: 6px 10px;
    font-size: 0.84rem;
}

.ds-contradiction-tag.is-even {
    background: rgba(247, 195, 95, 0.28);
    border-color: rgba(201, 95, 68, 0.34);
    color: var(--ink-900);
    transform: translateY(-1px);
}

.ds-contradiction-steps {
    display: grid;
    gap: 10px;
}

.ds-contradiction-board.is-compact .ds-contradiction-steps {
    gap: 8px;
}

.ds-contradiction-step {
    padding: 12px 14px;
    border-radius: 14px;
    border: 1px solid rgba(77, 107, 106, 0.1);
    background: rgba(255, 255, 255, 0.72);
    opacity: 0.22;
    transform: translateX(0);
    transition: opacity 220ms ease, transform 220ms ease, border-color 220ms ease, box-shadow 220ms ease;
}

.ds-contradiction-board.is-compact .ds-contradiction-step {
    padding: 9px 12px;
}

.ds-contradiction-step strong {
    display: block;
    margin-bottom: 4px;
}

.ds-contradiction-board.is-compact .ds-contradiction-step strong {
    margin-bottom: 2px;
    font-size: 0.88rem;
}

.ds-contradiction-step p {
    margin: 0;
    color: var(--ink-800);
    line-height: 1.55;
}

.ds-contradiction-board.is-compact .ds-contradiction-step p {
    font-size: 0.84rem;
    line-height: 1.4;
}

.ds-contradiction-step.is-visible {
    opacity: 1;
    transform: translateX(6px);
}

.ds-contradiction-step.is-current {
    border-color: rgba(201, 95, 68, 0.28);
    box-shadow: 0 10px 18px rgba(24, 32, 31, 0.08);
}

.ds-contradiction-alert {
    margin-top: 14px;
    padding: 13px 14px;
    border-radius: 16px;
    background: rgba(201, 95, 68, 0.12);
    border: 1px solid rgba(201, 95, 68, 0.22);
    color: var(--ink-900);
    font-weight: 700;
    opacity: 0;
    transform: translateY(8px);
    transition: opacity 220ms ease, transform 220ms ease;
}

.ds-contradiction-board.is-compact .ds-contradiction-alert {
    margin-top: 10px;
    padding: 10px 12px;
    font-size: 0.88rem;
}

.ds-contradiction-alert.is-visible {
    opacity: 1;
    transform: translateY(0);
}

.ds-progress {
    width: min(320px, 36vw);
    height: 10px;
    border-radius: 999px;
    background: rgba(77, 107, 106, 0.1);
    overflow: hidden;
    position: relative;
}

.ds-progress-bar {
    height: 100%;
    width: var(--slide-progress, 0%);
    border-radius: inherit;
    background: linear-gradient(90deg, var(--accent-coral), var(--accent-gold), var(--accent-sky));
    box-shadow: 0 4px 18px rgba(201, 95, 68, 0.2);
    transition: width 280ms var(--ease-emph);
}

@keyframes dsLineFlash {
    0% {
        filter: drop-shadow(0 0 0 rgba(201, 95, 68, 0));
    }
    50% {
        filter: drop-shadow(0 0 10px rgba(201, 95, 68, 0.5));
    }
    100% {
        filter: drop-shadow(0 0 0 rgba(201, 95, 68, 0));
    }
}

@keyframes dsPulseSoft {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.18);
    }
}

@media (max-width: 900px) {
    .ds-partition-grid,
    .ds-euler-hamilton-grid {
        grid-template-columns: 1fr;
    }
}

.ds-progress-bar::after {
    content: "";
    display: block;
    height: 100%;
    width: 44px;
    margin-left: auto;
    background: linear-gradient(90deg, rgba(255, 255, 255, 0), rgba(255, 255, 255, 0.44), rgba(255, 255, 255, 0));
    animation: dsSweep 2.4s linear infinite;
}

@keyframes dsFloat {
    0%, 100% {
        transform: translate3d(0, 0, 0) scale(1);
    }

    50% {
        transform: translate3d(18px, -20px, 0) scale(1.04);
    }
}

@keyframes dsRiseIn {
    from {
        opacity: 0;
        transform: translateY(18px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes dsStageEnter {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.985);
    }

    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

@keyframes dsVisualIn {
    from {
        opacity: 0;
        transform: translateX(20px) scale(0.98);
    }

    to {
        opacity: 1;
        transform: translateX(0) scale(1);
    }
}

@keyframes dsFeedbackIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes dsBuildIn {
    from {
        opacity: 0;
        transform: translateY(18px) scale(0.985);
        filter: blur(3px);
    }

    to {
        opacity: 1;
        transform: translateY(0) scale(1);
        filter: blur(0);
    }
}

@keyframes dsNodePop {
    from {
        transform: scale(0.88);
    }

    to {
        transform: scale(1);
    }
}

@keyframes dsSweep {
    from {
        transform: translateX(52px);
    }

    to {
        transform: translateX(-260px);
    }
}

@keyframes dsActivePress {
    from {
        transform: scale(0.98);
    }

    to {
        transform: scale(1);
    }
}

@media (max-width: 1180px) {
    .ds-shell,
    .ds-study-grid {
        grid-template-columns: 1fr;
    }

    .ds-sidebar,
    .ds-study-rail {
        position: static;
    }
}

@media (max-width: 900px) {
    .ds-app {
        padding: 16px;
    }

    body.ds-teach-mode {
        overflow: auto;
    }

    .ds-app.ds-app-teach,
    .ds-shell.ds-shell-teach,
    .ds-main.ds-main-teach {
        min-height: auto;
    }

    .ds-stage-body,
    .ds-grid-2,
    .ds-grid-3 {
        grid-template-columns: 1fr;
    }

    .ds-stage-card {
        min-height: auto;
    }

    .ds-main.ds-main-teach .ds-content-stack,
    .ds-main.ds-main-teach .ds-visual-panel {
        overflow: visible;
        padding-right: 0;
    }

    .ds-stage-header,
    .ds-stage-body,
    .ds-stage-footer,
    .ds-home-hero,
    .ds-study-slide {
        padding-left: 20px;
        padding-right: 20px;
    }

    .ds-topbar,
    .ds-study-topbar,
    .ds-home-topbar {
        align-items: flex-start;
        flex-direction: column;
    }

    .ds-footer-links {
        align-items: flex-start;
        flex-direction: column;
    }

    .ds-progress {
        width: 100%;
    }
}

@media (max-width: 600px) {
    .ds-app {
        padding: 12px;
    }

    .ds-sidebar,
    .ds-study-rail,
    .ds-topbar,
    .ds-study-topbar,
    .ds-home-topbar,
    .ds-home-hero,
    .ds-home-card,
    .ds-study-slide,
    .ds-stage-card {
        border-radius: 20px;
    }

    .ds-sidebar,
    .ds-home-hero,
    .ds-home-card,
    .ds-study-slide {
        padding: 18px;
    }

    .ds-stage-header,
    .ds-stage-body,
    .ds-stage-footer {
        padding-left: 16px;
        padding-right: 16px;
    }

    .ds-study-slide h2,
    .ds-stage-title,
    .ds-home-hero h1,
    .ds-sidebar h1 {
        font-size: clamp(1.7rem, 8vw, 2.35rem);
        line-height: 1.12;
    }

    .ds-stage-lead,
    .ds-study-slide .ds-stage-lead,
    .ds-home-subtitle,
    .ds-sidebar p {
        font-size: 0.98rem;
        line-height: 1.6;
    }

    .ds-topbar-left,
    .ds-topbar-right,
    .ds-home-actions,
    .ds-footer-links,
    .ds-mode-switch {
        width: 100%;
    }

    .ds-mode-switch {
        grid-template-columns: 1fr;
    }

    .ds-mode-button,
    .ds-link-button,
    .ds-launch-link {
        width: 100%;
    }

    .ds-topic-picker {
        width: 100%;
        justify-content: space-between;
        border-radius: 14px;
    }

    .ds-topic-select {
        min-width: 0;
        width: 100%;
        text-align: right;
    }

    .ds-pill,
    .ds-build-chip,
    .ds-chip {
        max-width: 100%;
        white-space: normal;
        line-height: 1.3;
    }

    .ds-card-grid {
        grid-template-columns: 1fr;
    }

    .ds-mini-card,
    .ds-proof-box,
    .ds-note-box,
    .ds-table-box,
    .ds-grid-box,
    .ds-exercise-box,
    .ds-summary-box,
    .ds-quiz-box,
    .ds-svg-panel,
    .ds-widget-card {
        padding: 14px;
    }

    .ds-point-list li {
        padding: 12px 14px;
    }

    .ds-step-list li {
        grid-template-columns: 28px minmax(0, 1fr);
        gap: 10px;
    }

    .ds-step-list span {
        width: 28px;
        height: 28px;
        font-size: 0.82rem;
    }

    .ds-formula {
        font-size: 0.98rem;
        padding: 12px 14px;
    }

    .ds-table-box table {
        font-size: 0.88rem;
    }

    .ds-table-box th,
    .ds-table-box td {
        padding: 8px 9px;
    }

    .ds-embed {
        min-height: 260px;
    }
}

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

    *,
    *::before,
    *::after {
        animation: none !important;
        transition: none !important;
    }
}