/* 本节资源中心；颜色随现有浅色 / 深色主题变量变化。 */
.cr-center { margin: 30px 0 38px; border: 1px solid var(--border); border-radius: var(--radius-lg); background: var(--surface); box-shadow: var(--shadow-sm); overflow: hidden; min-width: 0; }
.cr-center [hidden] { display: none !important; }
.cr-center :is(button, input, select, summary, [tabindex="0"]):focus-visible { outline: 3px solid var(--accent-border); outline-offset: 3px; }
.cr-center button, .cr-center select, .cr-center input { font: inherit; }
.cr-center button { cursor: pointer; }
.cr-center button:disabled { cursor: default; opacity: .52; }
.cr-heading { display: flex; align-items: end; justify-content: space-between; gap: 20px; padding: 25px 28px 21px; }
.cr-heading h2 { margin: 6px 0 0; color: var(--text); font-size: 20px; line-height: 1.45; letter-spacing: -.4px; }
.cr-heading > p { margin: 0 0 3px; color: var(--text-soft); font-size: 12.5px; }
.cr-eyebrow { margin: 0 0 8px; color: var(--accent-ink); font-size: 12px; font-weight: 650; letter-spacing: .04em; }
.cr-tabs { display: grid; grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 3px; padding: 0 20px; border-bottom: 1px solid var(--border); overflow-x: auto; scrollbar-width: thin; }
.cr-tabs [role="tab"] { position: relative; display: flex; align-items: center; justify-content: center; gap: 7px; padding: 16px 5px 18px; border: 0; border-radius: 9px 9px 0 0; background: transparent; color: var(--text-soft); font-size: 13.5px; font-weight: 550; white-space: nowrap; }
.cr-tabs [role="tab"]::after { position: absolute; right: 12px; bottom: 0; left: 12px; height: 3px; border-radius: 3px 3px 0 0; background: transparent; content: ''; }
.cr-tabs [role="tab"]:hover { color: var(--text); background: var(--surface-subtle); }
.cr-tabs [aria-selected="true"] { color: var(--text); font-weight: 750; background: var(--surface-raised); }
.cr-tabs [aria-selected="true"]::after { background: var(--accent); }
.cr-tab-number { color: var(--text-faint); font: 12px var(--mono); }
.cr-tabs [aria-selected="true"] .cr-tab-number { color: var(--accent-ink); }
.cr-panel { padding: 26px 28px 28px; min-height: 330px; min-width: 0; }
.cr-panel :is(h3, p, li) { overflow-wrap: anywhere; }
.cr-panel h3 { margin: 0; color: var(--text); font-size: 16px; line-height: 1.55; }
.cr-panel p, .cr-panel li { color: var(--text-soft); font-size: 13.5px; line-height: 1.85; }
.cr-mode-tabs { display: inline-flex; gap: 4px; padding: 4px; margin-bottom: 22px; border: 1px solid var(--border); border-radius: 10px; background: var(--surface-subtle); }
.cr-mode-tabs button { padding: 8px 16px; color: var(--text-soft); background: transparent; border: 0; border-radius: 7px; font-size: 13.5px; }
.cr-mode-tabs [aria-selected="true"] { color: var(--text); background: var(--surface); box-shadow: var(--shadow-sm); font-weight: 650; }
.cr-original-figure { display: grid; place-items: center; min-width: 0; }
.cr-original-figure > * { width: 100%; max-width: 660px; }
.cr-original-figure svg { max-width: 100%; height: auto; }
.cr-figure-note { max-width: 660px; margin: 18px auto 0; padding: 15px 18px; border-left: 3px solid var(--accent); border-radius: 0 8px 8px 0; background: var(--surface-raised); }
.cr-limit { border: 1px solid var(--border); border-radius: 13px; background: var(--bg); padding: 23px; }
.cr-limit-heading, .cr-panel-heading { display: flex; justify-content: space-between; align-items: center; gap: 20px; margin-bottom: 22px; }
.cr-limit-heading .cr-eyebrow, .cr-panel-heading .cr-eyebrow { margin-bottom: 5px; }
.cr-limit-plot { display: block; width: min(100%, 600px); height: auto; margin: 0 auto 8px; color: var(--text-soft); overflow: visible; }
.cr-limit-plot text { fill: currentColor; font-size: 12px; }
.cr-grid { stroke: var(--border); stroke-width: 1; fill: none; }
.cr-axis { stroke: var(--text-faint); stroke-width: 1.5; fill: none; }
.cr-function { stroke: var(--accent-ink); stroke-width: 3; fill: none; stroke-linecap: round; }
.cr-guide { stroke: var(--text-faint); stroke-width: 1.5; stroke-dasharray: 5 5; fill: none; }
.cr-target { fill: var(--surface); stroke: var(--accent-ink); stroke-width: 2; }
.cr-moving-guide { stroke: var(--blue); stroke-width: 1.5; stroke-dasharray: 3 4; fill: none; }
.cr-moving-point { fill: var(--blue); stroke: var(--surface); stroke-width: 2; }
.cr-limit-controls { display: grid; grid-template-columns: minmax(130px, .7fr) minmax(0, 1.8fr); gap: 25px; align-items: start; }
.cr-limit-controls label { display: grid; gap: 10px; color: var(--text-soft); font-size: 12.5px; font-weight: 550; }
.cr-limit-controls select { width: 100%; min-height: 38px; padding: 8px 12px; color: var(--text); background: var(--surface); border: 1px solid var(--border-strong); border-radius: 7px; }
.cr-range-label input { width: 100%; margin: 8px 0 0; accent-color: var(--accent-ink); cursor: pointer; min-height: 20px; }
.cr-range-label > span { display: flex; justify-content: space-between; gap: 8px; }
.cr-range-label small { color: var(--text-faint); font-size: 12px; font-weight: 400; }
.cr-limit-values { display: block; padding: 12px 14px; margin-top: 18px; color: var(--blue); background: var(--blue-soft); border-radius: 8px; font: 12.5px/1.8 var(--mono); overflow-wrap: anywhere; }
.cr-panel .cr-footnote { color: var(--text-faint); margin: 14px 0 0; font-size: 12.5px; line-height: 1.8; }
.cr-source-figure { margin-top: 18px; padding-top: 15px; border-top: 1px solid var(--border); }
.cr-source-figure > summary, .cr-solution > summary { color: var(--text-soft); cursor: pointer; font-size: 13.5px; line-height: 1.8; }
.cr-source-figure[open] > summary { margin-bottom: 15px; }
.cr-pill, .cr-count { display: inline-flex; align-items: center; flex-shrink: 0; min-height: 27px; padding: 4px 9px; border: 1px solid var(--accent-border); border-radius: 7px; background: var(--accent-soft); color: var(--accent-ink); font: 12px/1.5 var(--mono); white-space: nowrap; }
.cr-explanations { display: grid; gap: 22px; }
.cr-explanations article { display: grid; grid-template-columns: 28px minmax(0, 1fr); gap: 13px; }
.cr-step-index { display: grid; place-items: center; width: 26px; height: 26px; margin-top: 2px; border: 1px solid var(--border); border-radius: 8px; color: var(--text-soft); background: var(--surface-subtle); font: 12px var(--mono); }
.cr-explanations h3 { font-size: 15px; }
.cr-explanations p { margin: 6px 0 0; white-space: pre-line; }
.cr-example { padding: 21px 23px; background: var(--surface-subtle); border: 1px solid var(--border); border-radius: 12px; }
.cr-explanations + .cr-example { margin-top: 25px; }
.cr-example h3 { font-size: 15px; font-weight: 650; }
.cr-example ol { display: grid; gap: 9px; margin: 18px 0 0; padding-left: 22px; }
.cr-answer { display: grid; grid-template-columns: auto minmax(0, 1fr); align-items: baseline; gap: 12px; margin-top: 18px; padding-top: 14px; border-top: 1px solid var(--border); font-size: 13.5px; }
.cr-answer strong { color: var(--accent-ink); }
.cr-answer p { margin: 0; }
.cr-goal { display: flex; align-items: baseline; gap: 14px; margin: 0 0 24px; padding: 14px 17px; background: var(--surface-raised); border-left: 3px solid var(--accent); border-radius: 0 8px 8px 0; }
.cr-goal strong { color: var(--accent-ink); white-space: nowrap; font-size: 12.5px; }
.cr-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 9px; }
.cr-button { display: inline-flex; align-items: center; justify-content: center; gap: 9px; min-height: 38px; padding: 9px 15px; border: 1px solid var(--border-strong); border-radius: 8px; color: var(--text); background: var(--surface); font-size: 13.5px !important; font-weight: 600 !important; text-align: center; line-height: 1.5; }
.cr-button:hover { border-color: var(--accent-border); background: var(--surface-raised); }
.cr-button.is-primary { background: var(--accent); border-color: var(--accent); color: #29230e; }
.cr-button.is-primary:hover { background: var(--accent-hover); }
.cr-button.is-subtle { background: transparent; border-color: var(--border); color: var(--text-soft); }
.cr-button.is-subtle:hover { background: var(--surface-subtle); color: var(--text); }
.cr-empty { display: grid; justify-items: center; align-content: center; padding: 34px 18px; min-height: 265px; text-align: center; }
.cr-empty-mark { display: grid; place-items: center; width: 52px; height: 52px; margin-bottom: 15px; border: 1px solid var(--border); border-radius: 15px; color: var(--accent-ink); background: var(--surface-raised); font-size: 24px; }
.cr-empty p { max-width: 460px; margin: 9px 0 0; }
.cr-empty .cr-button { margin-top: 22px; }
.cr-video-wrap video { display: block; width: 100%; max-height: 540px; border-radius: 12px; background: #111; aspect-ratio: 16 / 9; }
.cr-question-group { margin-top: 25px; }
.cr-question-group > h3 { display: flex; align-items: center; gap: 9px; font-size: 15px; }
.cr-question-group > h3 > span { color: var(--text-faint); font: 12px var(--mono); }
.cr-question-group > .cr-footnote { margin: 6px 0 12px; }
.cr-question-list { display: grid; gap: 10px; }
.cr-question { border: 1px solid var(--border); border-radius: 11px; background: var(--surface); overflow: hidden; }
.cr-question > summary { display: flex; align-items: center; justify-content: space-between; gap: 16px; padding: 16px 18px; cursor: pointer; list-style: none; }
.cr-question > summary::-webkit-details-marker { display: none; }
.cr-question > summary:hover { background: var(--surface-subtle); }
.cr-question-title { display: block; color: var(--text); font-size: 13.5px; font-weight: 650; line-height: 1.65; }
.cr-question-meta { display: block; margin-top: 4px; color: var(--text-faint); font-size: 12px; line-height: 1.7; }
.cr-question-chevron { color: var(--text-faint); font-size: 17px; }
.cr-question[open] .cr-question-chevron { transform: rotate(180deg); }
.cr-question-body { padding: 0 18px 18px; border-top: 1px solid var(--border); }
.cr-question-body > p { white-space: pre-line; }
.cr-question .cr-last-attempt { display: inline-block; padding: 5px 10px; margin: 7px 0 0; border-radius: 6px; color: var(--text-soft); background: var(--surface-subtle); font-size: 12.5px; line-height: 1.7; }
.cr-question .cr-last-attempt.is-correct { color: var(--success); background: var(--success-soft); }
.cr-question .cr-last-attempt.is-wrong { color: var(--warning); background: var(--warning-soft); }
.cr-question-options { display: grid; gap: 6px; margin: 12px 0; padding-left: 24px; }
.cr-solution { padding: 13px 0; margin: 12px 0; border-block: 1px solid var(--border); }
.cr-solution p { margin: 10px 0 0; white-space: pre-line; }
.cr-quiz { border: 0; margin: 0 0 20px; padding: 0; min-width: 0; }
.cr-quiz legend { float: none; width: 100%; margin: 0 0 18px; padding: 0; color: var(--text); font-size: 15px; line-height: 1.9; font-weight: 600; overflow-wrap: anywhere; }
.cr-quiz-options { display: grid; gap: 10px; }
.cr-quiz-option { display: grid; grid-template-columns: 18px 27px minmax(0, 1fr); align-items: center; gap: 12px; padding: 13px 16px; border: 1px solid var(--border); border-radius: 10px; color: var(--text-soft); background: var(--surface); font-size: 13.5px; line-height: 1.75; cursor: pointer; }
.cr-quiz-option:hover { border-color: var(--accent-border); }
.cr-quiz-option:has(input:checked) { border-color: var(--accent-border); background: var(--surface-raised); color: var(--text); }
.cr-quiz-option input { width: 17px; height: 17px; margin: 0; accent-color: var(--accent-ink); }
.cr-option-letter { color: var(--text-soft); font: 13.5px var(--mono); }
.cr-feedback { margin-top: 18px; padding: 16px 18px; border: 1px solid var(--warning-border); border-radius: 10px; background: var(--warning-soft); color: var(--warning); font-size: 13.5px; }
.cr-feedback.is-correct { color: var(--success); border-color: var(--success-border); background: var(--success-soft); }
.cr-feedback p { margin: 6px 0 0; color: var(--text-soft); }
@media (max-width: 1000px) {
  .cr-tabs { display: flex; gap: 8px; padding: 0 15px; }
  .cr-tabs [role="tab"] { flex: 0 0 auto; padding-inline: 13px; }
  .cr-tab-number { display: none; }
}
@media (max-width: 640px) {
  .cr-center { margin-top: 23px; border-radius: 14px; }
  .cr-heading { align-items: start; flex-direction: column; gap: 9px; padding: 21px 18px 17px; }
  .cr-heading h2 { font-size: 19px; }
  .cr-heading > p { font-size: 12.5px; }
  .cr-tabs { padding: 0 9px; gap: 2px; }
  .cr-tabs [role="tab"] { padding: 14px 11px 16px; }
  .cr-panel { padding: 20px 16px 23px; }
  .cr-limit { padding: 16px 13px; }
  .cr-limit-heading, .cr-panel-heading { flex-wrap: wrap; gap: 12px; }
  .cr-limit-heading h3 { font-size: 15px; }
  .cr-limit-controls { grid-template-columns: minmax(0, 1fr); gap: 18px; }
  .cr-limit-controls select { max-width: 220px; }
  .cr-limit-values { font-size: 12px; }
  .cr-mode-tabs { display: flex; }
  .cr-mode-tabs button { flex: 1; padding-inline: 9px; }
  .cr-explanations article { grid-template-columns: 25px minmax(0, 1fr); gap: 10px; }
  .cr-example { padding: 17px 16px; }
  .cr-goal { flex-direction: column; gap: 5px; }
  .cr-question > summary { padding: 14px; }
  .cr-question-body { padding-inline: 14px; }
  .cr-quiz-option { grid-template-columns: 18px 20px minmax(0, 1fr); gap: 8px; padding: 12px; }
  .cr-empty { padding: 28px 8px; }
  .cr-answer { grid-template-columns: minmax(0, 1fr); gap: 5px; }
}
@media (prefers-reduced-motion: reduce) {
  .cr-center *, .cr-center *::before, .cr-center *::after { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}