:root {
    --ex-ink: #23334b;
    --ex-muted: #73839a;
    --ex-line: #dfe7f0;
    --ex-paper: #f4f7fb;
    --ex-accent: #4f63e6;
    --ex-accent-2: #7a5cf0;
}

.exercise-page {
    background: var(--ex-paper);
    color: var(--ex-ink);
    font-family: var(--site-nav-font, system-ui, -apple-system, "Segoe UI", "Microsoft YaHei", sans-serif);
    min-height: calc(100vh - 66px);
    padding: 28px clamp(18px, 3.5vw, 68px) 64px;
}

.exercise-page > * {
    margin-left: auto;
    margin-right: auto;
    max-width: 1240px;
}

.exercise-breadcrumb {
    color: var(--ex-muted);
    font-size: 12px;
    margin-bottom: 12px;
}

.exercise-breadcrumb a {
    color: var(--ex-accent);
    text-decoration: none;
}

.exercise-breadcrumb span {
    padding: 0 5px;
}

.exercise-hero {
    align-items: end;
    background: linear-gradient(135deg, #293c59, #4f63e6);
    border-radius: 18px;
    box-shadow: 0 20px 50px rgba(40, 61, 98, .18);
    color: #fff;
    display: flex;
    justify-content: space-between;
    overflow: hidden;
    padding: 30px 36px;
    position: relative;
}

.exercise-hero:after {
    border: 1px solid rgba(255, 255, 255, .14);
    border-radius: 50%;
    content: "";
    height: 280px;
    position: absolute;
    right: -80px;
    top: -150px;
    width: 280px;
}

.exercise-hero h1 {
    font-size: 29px;
    margin: 0 0 9px;
}

.exercise-hero p {
    color: #dbe4f5;
    margin: 0;
    max-width: 720px;
}

.exercise-eyebrow {
    color: inherit;
    font-size: 10px;
    font-weight: 800;
    letter-spacing: .2em;
    margin: 0 0 9px;
    opacity: .72;
}

.exercise-hero-stat {
    align-items: center;
    background: rgba(255, 255, 255, .1);
    border: 1px solid rgba(255, 255, 255, .2);
    border-radius: 14px;
    display: flex;
    flex: 0 0 auto;
    flex-direction: column;
    margin-left: 24px;
    padding: 14px 22px;
    position: relative;
    z-index: 1;
}

.exercise-hero-stat strong {
    font-size: 30px;
    line-height: 1.1;
}

.exercise-hero-stat span {
    color: #d5defb;
    font-size: 11px;
    margin-top: 4px;
}

.exercise-progress-strip,
.exercise-summary-strip {
    align-items: center;
    background: #fff;
    border: 1px solid var(--ex-line);
    border-radius: 14px;
    display: flex;
    flex-wrap: wrap;
    gap: 24px;
    margin-top: 16px;
    padding: 16px 20px;
}

.exercise-summary-item {
    display: flex;
    flex-direction: column;
    gap: 3px;
}

.exercise-summary-item span {
    color: var(--ex-muted);
    font-size: 11px;
}

.exercise-summary-item strong {
    color: var(--ex-ink);
    font-size: 22px;
    font-variant-numeric: tabular-nums;
}

.exercise-summary-link {
    color: var(--ex-accent);
    font-size: 12px;
    font-weight: 700;
    margin-left: auto;
    text-decoration: none;
    white-space: nowrap;
}

.exercise-summary-link:hover {
    text-decoration: underline;
}

.exercise-filters {
    background: #fff;
    border: 1px solid var(--ex-line);
    border-radius: 14px;
    margin-top: 16px;
    padding: 13px 18px;
}

.exercise-filters form {
    align-items: end;
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.exercise-filters label {
    display: flex;
    flex-direction: column;
    gap: 5px;
}

.exercise-filters label span {
    color: var(--ex-muted);
    font-size: 10px;
    font-weight: 700;
    letter-spacing: .06em;
}

.exercise-filters select {
    background: #f7f9fc;
    border: 1px solid #dbe4ef;
    border-radius: 9px;
    color: var(--ex-ink);
    font-family: inherit;
    font-size: 12px;
    min-width: 150px;
    padding: 8px 10px;
}

.exercise-filter-button,
.exercise-submit {
    background: linear-gradient(135deg, var(--ex-accent), var(--ex-accent-2));
    border: 0;
    border-radius: 9px;
    box-shadow: 0 7px 18px rgba(79, 99, 230, .2);
    color: #fff;
    cursor: pointer;
    font-family: inherit;
    font-size: 12px;
    font-weight: 700;
    padding: 9px 15px;
}

.exercise-filter-button:hover,
.exercise-submit:hover {
    box-shadow: 0 10px 24px rgba(79, 99, 230, .28);
}

.exercise-filter-clear {
    color: var(--ex-muted);
    font-size: 12px;
    padding: 9px 4px;
    text-decoration: none;
}

.exercise-group {
    margin-top: 26px;
}

.exercise-group-heading {
    align-items: baseline;
    display: flex;
    gap: 10px;
    justify-content: space-between;
    margin-bottom: 12px;
}

.exercise-group-heading h2 {
    font-size: 21px;
    margin: 0;
}

.exercise-group-heading span {
    color: var(--ex-muted);
    font-size: 12px;
}

.exercise-grid {
    display: grid;
    gap: 14px;
    grid-template-columns: repeat(auto-fill, minmax(290px, 1fr));
}

.exercise-card {
    background: #fff;
    border: 1px solid var(--ex-line);
    border-radius: 14px;
    color: var(--ex-ink);
    display: flex;
    flex-direction: column;
    min-height: 180px;
    padding: 18px 20px;
    text-decoration: none;
    transition: transform .16s ease, box-shadow .16s ease, border-color .16s ease;
}

.exercise-card:hover {
    border-color: #b9c5f2;
    box-shadow: 0 14px 32px rgba(57, 77, 112, .1);
    color: var(--ex-ink);
    text-decoration: none;
    transform: translateY(-2px);
}

.exercise-card-top,
.exercise-detail-head .exercise-card-top {
    align-items: center;
    display: flex;
    gap: 8px;
    justify-content: space-between;
}

.exercise-type {
    border-radius: 99px;
    display: inline-block;
    font-size: 10px;
    font-weight: 800;
    letter-spacing: .04em;
    padding: 4px 8px;
}

.exercise-type-calculation {
    background: #eef1ff;
    color: #3346c9;
}

.exercise-type-trace {
    background: #e6f6f1;
    color: #237a64;
}

.exercise-type-design {
    background: #fff3e3;
    color: #9a5a12;
}

.exercise-type-experiment {
    background: #f3eefe;
    color: #5f3ab5;
}

.exercise-difficulty {
    color: #94a3b8;
    font-size: 10px;
    font-weight: 700;
}

.exercise-card h3 {
    font-size: 17px;
    margin: 14px 0 8px;
}

.exercise-card p {
    color: var(--ex-muted);
    flex: 1;
    font-size: 12px;
    line-height: 1.65;
    margin: 0;
}

.exercise-card footer {
    align-items: center;
    border-top: 1px solid #edf1f5;
    color: #8b98aa;
    display: flex;
    font-size: 11px;
    gap: 10px;
    justify-content: space-between;
    margin-top: 14px;
    padding-top: 11px;
}

.exercise-status.ok {
    color: #237a46;
    font-weight: 700;
}

.exercise-status.bad {
    color: #a53434;
    font-weight: 700;
}

.exercise-detail {
    margin-top: 8px;
    max-width: 900px;
}

.exercise-detail-head {
    margin-bottom: 18px;
}

.exercise-detail-head h1 {
    font-size: 30px;
    margin: 12px 0 8px;
}

.exercise-detail-meta {
    color: var(--ex-muted);
    font-size: 12px;
    margin: 0;
}

.exercise-prompt,
.exercise-form,
.exercise-explanation {
    background: #fff;
    border: 1px solid var(--ex-line);
    border-radius: 16px;
    box-shadow: 0 12px 30px rgba(56, 82, 115, .05);
    padding: 24px 28px;
}

.exercise-prompt {
    font-size: 14px;
    line-height: 1.8;
}

.exercise-prompt p:first-child {
    margin-top: 0;
}

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

.exercise-prompt pre {
    background: #172033;
    border-radius: 10px;
    color: #e7edf7;
    overflow-x: auto;
    padding: 14px 16px;
}

.exercise-prompt code {
    background: #f1f4f9;
    border-radius: 4px;
    padding: 1px 5px;
}

.exercise-prompt pre code {
    background: transparent;
    padding: 0;
}

.exercise-form {
    margin-top: 16px;
}

.exercise-label,
.exercise-options legend {
    color: var(--ex-ink);
    display: block;
    font-size: 13px;
    font-weight: 800;
    margin-bottom: 9px;
}

.exercise-form input[type="text"],
.exercise-form textarea {
    background: #f8fafd;
    border: 1px solid #dbe4ef;
    border-radius: 10px;
    box-sizing: border-box;
    color: var(--ex-ink);
    font-family: inherit;
    font-size: 14px;
    outline: none;
    padding: 11px 13px;
    width: 100%;
}

.exercise-form input[type="text"]:focus,
.exercise-form textarea:focus {
    background: #fff;
    border-color: #aebcf5;
    box-shadow: 0 0 0 4px rgba(79, 99, 230, .08);
}

.exercise-options {
    border: 0;
    margin: 0;
    padding: 0;
}

.exercise-option {
    align-items: flex-start;
    background: #f8fafd;
    border: 1px solid #e4ebf4;
    border-radius: 10px;
    cursor: pointer;
    display: flex;
    font-size: 13px;
    gap: 9px;
    line-height: 1.55;
    margin-top: 8px;
    padding: 11px 13px;
}

.exercise-option:hover {
    background: #f3f6fd;
    border-color: #c7d2fe;
}

.exercise-option input {
    margin-top: 3px;
}

.exercise-option-key {
    color: var(--ex-accent);
    font-weight: 800;
}

.exercise-actions {
    align-items: center;
    display: flex;
    gap: 14px;
    margin-top: 16px;
}

.exercise-submit {
    font-size: 13px;
    padding: 11px 18px;
}

.exercise-submit:disabled {
    cursor: wait;
    opacity: .7;
}

.exercise-login-note {
    color: var(--ex-muted);
    font-size: 11px;
}

.exercise-result {
    border-radius: 14px;
    margin-top: 16px;
    padding: 16px 20px;
}

.exercise-result.correct {
    background: #e9f8ef;
    border: 1px solid #bfe8cf;
    color: #1f6b3f;
}

.exercise-result.wrong {
    background: #fdf0f0;
    border: 1px solid #f2caca;
    color: #8f2f2f;
}

.exercise-result strong {
    display: block;
    font-size: 15px;
    margin-bottom: 5px;
}

.exercise-result p {
    font-size: 13px;
    line-height: 1.6;
    margin: 5px 0;
}

.exercise-result small {
    display: block;
    font-size: 11px;
    margin-top: 7px;
    opacity: .8;
}

.exercise-answer-line {
    font-weight: 700;
}

.exercise-explanation {
    margin-top: 16px;
}

.exercise-explanation:empty {
    display: none;
}

.exercise-metrics {
    display: grid;
    gap: 14px;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    margin-top: 16px;
}

.exercise-metrics article {
    background: #fff;
    border: 1px solid var(--ex-line);
    border-radius: 13px;
    padding: 18px 20px;
}

.exercise-metrics span {
    color: var(--ex-muted);
    display: block;
    font-size: 12px;
}

.exercise-metrics strong {
    display: block;
    font-size: 27px;
    font-variant-numeric: tabular-nums;
    margin-top: 6px;
}

.exercise-section {
    background: #fff;
    border: 1px solid var(--ex-line);
    border-radius: 16px;
    margin-top: 20px;
    padding: 24px 28px;
}

.exercise-section-heading {
    align-items: end;
    display: flex;
    gap: 16px;
    justify-content: space-between;
    margin-bottom: 14px;
}

.exercise-section-heading h2 {
    font-size: 21px;
    margin: 0;
}

.exercise-section-heading p {
    color: var(--ex-muted);
    font-size: 12px;
    margin: 0;
    max-width: 600px;
}

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

.exercise-table {
    border-collapse: collapse;
    font-size: 13px;
    width: 100%;
}

.exercise-table th {
    background: #f7f9fc;
    border-bottom: 1px solid var(--ex-line);
    color: #7c8ca2;
    font-size: 10px;
    font-weight: 800;
    letter-spacing: .08em;
    padding: 9px 11px;
    text-align: left;
    white-space: nowrap;
}

.exercise-table td {
    border-bottom: 1px solid #edf1f5;
    padding: 11px;
}

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

.exercise-empty-text {
    color: var(--ex-muted);
    font-size: 13px;
    margin: 0;
}

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

.wrong-item {
    align-items: center;
    background: #fbfcfe;
    border: 1px solid #e4ebf4;
    border-radius: 11px;
    color: var(--ex-ink);
    display: flex;
    gap: 14px;
    justify-content: space-between;
    padding: 12px 14px;
    text-decoration: none;
    transition: background .16s ease, border-color .16s ease;
}

.wrong-item:hover {
    background: #f6f8fe;
    border-color: #c7d2fe;
    color: var(--ex-ink);
    text-decoration: none;
}

.wrong-item > div {
    align-items: center;
    display: flex;
    gap: 9px;
}

.wrong-item > span,
.wrong-item small {
    color: var(--ex-muted);
    font-size: 11px;
}

/* Course page entry points */
.course-hero-side {
    align-items: center;
    display: flex;
    flex: 0 0 auto;
    gap: 18px;
}

.course-exercise-link {
    align-items: center;
    background: linear-gradient(135deg, #eef1ff, #f6f3ff);
    border: 1px solid #dfe5ff;
    border-radius: 14px;
    color: #3346c9;
    display: inline-flex;
    flex-direction: column;
    gap: 4px;
    padding: 11px 16px;
    text-decoration: none;
    transition: transform .16s ease, box-shadow .16s ease;
}

.course-exercise-link:hover {
    box-shadow: 0 10px 24px rgba(79, 99, 230, .14);
    color: #2738b5;
    text-decoration: none;
    transform: translateY(-1px);
}

.course-exercise-kicker {
    font-size: 8px;
    font-weight: 800;
    letter-spacing: .16em;
    opacity: .6;
}

.course-exercise-link strong {
    font-size: 15px;
}

.course-exercise-link .fa {
    font-size: 10px;
}

.directory-exercise {
    color: #9aa8ba;
    display: inline;
    font-size: 10px;
    font-weight: 400;
    margin-left: 4px;
    padding: 0;
    text-decoration: none;
    white-space: nowrap;
}

.directory-exercise:hover {
    color: #425f86;
    text-decoration: underline;
}

.exercise-empty {
    background: #fff;
    border: 1px dashed #d7e0ec;
    border-radius: 16px;
    margin-top: 26px;
    padding: 42px 24px;
    text-align: center;
}

.exercise-empty h2 {
    font-size: 20px;
    margin: 0 0 8px;
}

.exercise-empty p {
    color: var(--ex-muted);
    margin: 0;
}

@media (max-width: 900px) {
    .exercise-hero {
        align-items: flex-start;
        display: block;
        padding: 26px;
    }

    .exercise-hero-stat {
        align-items: flex-start;
        margin: 18px 0 0;
    }

    .exercise-section-heading {
        align-items: flex-start;
        display: block;
    }

    .exercise-section-heading p {
        margin-top: 6px;
    }

    .course-hero-side {
        align-items: flex-start;
        flex-direction: column;
        gap: 12px;
        margin-top: 18px;
    }
}

@media (max-width: 650px) {
    .exercise-page {
        padding: 20px 12px 48px;
    }

    .exercise-hero {
        padding: 22px;
    }

    .exercise-hero h1 {
        font-size: 24px;
    }

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

    .exercise-detail-head h1 {
        font-size: 25px;
    }

    .exercise-prompt,
    .exercise-form,
    .exercise-explanation,
    .exercise-section {
        padding: 18px;
    }

    .exercise-progress-strip,
    .exercise-summary-strip {
        gap: 14px;
    }

    .exercise-summary-link {
        margin-left: 0;
        width: 100%;
    }

    .wrong-item {
        align-items: flex-start;
        flex-direction: column;
    }
}

.exercise-result.pending {
    background: #f7f9fc;
    border: 1px solid #d8e1ec;
    color: #425f86;
}

.exercise-score {
    font-weight: 700;
}

.exercise-criteria {
    font-size: 13px;
    line-height: 1.6;
    margin: 8px 0 0 18px;
}

.exercise-criteria li {
    margin: 3px 0;
}

.exercise-rubric {
    background: #fffaf0;
    border: 1px solid #f0dcc0;
    border-radius: 14px;
    margin: 16px 0;
    padding: 16px 20px;
}

.exercise-rubric h2 {
    color: #8a5715;
    font-size: 16px;
    margin: 0 0 8px;
}

.exercise-rubric ul {
    margin: 0;
    padding-left: 18px;
}

.exercise-rubric li {
    font-size: 13px;
    line-height: 1.55;
    margin: 6px 0;
}

.exercise-rubric-points {
    color: #9a5a12;
    font-weight: 700;
    margin-left: 8px;
}

.exercise-rubric small {
    color: #94a3b8;
    display: block;
    margin-top: 2px;
}

.exercise-rubric p {
    color: #8a5715;
    font-size: 12px;
    margin: 10px 0 0;
}

.exercise-webgpu {
    margin-top: 16px;
}

.exercise-shader {
    background: #1e293b;
    border: 0;
    border-radius: 12px;
    box-sizing: border-box;
    color: #e2e8f0;
    font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
    font-size: 13px;
    line-height: 1.6;
    min-height: 320px;
    padding: 16px;
    resize: vertical;
    tab-size: 2;
    width: 100%;
}

.exercise-webgpu-status {
    margin-top: 16px;
}

.webgpu-overall {
    font-weight: 700;
    margin: 0 0 8px;
}

.webgpu-overall.pass {
    color: #1f6b3f;
}

.webgpu-overall.fail {
    color: #8f2f2f;
}

.webgpu-tests {
    list-style: none;
    margin: 0;
    padding: 0;
}

.webgpu-tests li {
    font-size: 13px;
    line-height: 1.6;
    margin: 4px 0;
}

.webgpu-pass {
    color: #1f6b3f;
}

.webgpu-fail {
    color: #8f2f2f;
}

.exercise-hint {
    font-size: 13px;
    margin-top: 16px;
}

.exercise-hint summary {
    color: #5f6f86;
    cursor: pointer;
}

.exercise-hint pre {
    background: #f7f9fc;
    border: 1px solid #e2e8f0;
    border-radius: 10px;
    margin-top: 8px;
    overflow: auto;
    padding: 12px;
    white-space: pre-wrap;
}

/* .course-directory a 默认是 flex，习题标签要跟着标题文字走，必须改回 inline */
.course-directory .directory-row > a.directory-exercise {
    color: #9aa8ba;
    display: inline;
    flex: 0 0 auto;
    font-size: 10px;
    font-weight: 400;
    gap: 0;
    margin-left: 4px;
    padding: 0;
}