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var(--paper-aging-image);background-position:0 0,-61px -143px;background-repeat:no-repeat,repeat;background-size:auto, var(--paper-aging-size);-webkit-backdrop-filter:blur(9px);backdrop-filter:blur(9px);min-height:3.75rem;padding:0 2.625rem}.learner-banner.paper-debris-surface.paper-debris-surface{background-image:linear-gradient(#ffffff47, #ffffff47), var(--paper-debris-images), var(--paper-aging-image);background-position:0 0, var(--paper-debris-positions), -61px -143px;background-repeat:no-repeat,repeat,repeat,repeat;background-size:auto, var(--paper-debris-sizes), var(--paper-aging-size);background-blend-mode:screen, multiply, multiply, normal}.learner-brand{color:#222421;letter-spacing:.08em;white-space:nowrap;gap:.75rem;min-width:0;font-family:Songti SC,STSong,SimSun,Noto Serif CJK SC,Georgia,serif;font-size:1.625rem;font-weight:700}.learner-brand-seal{object-fit:contain;flex:0 0 40px;width:40px;height:40px;display:block}.learner-brand-title{text-overflow:ellipsis;overflow:hidden}.learner-actions{flex-shrink:0;gap:1.25rem;font-family:ui-sans-serif,-apple-system,BlinkMacSystemFont,Segoe UI,PingFang SC,Hiragino Sans GB,Microsoft YaHei,sans-serif}.learner-actions>a{color:#454741;font-size:.8125rem;font-weight:600}.learner-actions>a[aria-current=page]{color:var(--accent);text-underline-offset:8px;font-weight:700;text-decoration:underline;text-decoration-thickness:2px}.learner-page{min-height:calc(100dvh - 3.75rem)}.learner-reader.course-layout{color:#222421;background:0 0;grid-template-columns:19rem minmax(0,1fr);width:min(100%,100rem);height:calc(100dvh - 3.75rem);min-height:0;margin:0 auto;line-height:1.64;display:grid;overflow:clip}.learner-reader .course-breadcrumb a{color:inherit;text-decoration:none}.learner-reader .course-breadcrumb a:hover,.learner-reader .course-breadcrumb a:focus-visible{text-underline-offset:3px;text-decoration:underline}.learner-reader .course-sidebar{--print-rule-color:#2a29254f;--print-mask-x:-719px;--print-mask-y:-89px;background:0 0;border-right:0;flex-direction:column;height:100%;min-height:0;padding:0;display:flex;overflow:visible}.learner-reader .course-sidebar-scroll{overscroll-behavior:contain;flex-direction:column;width:100%;height:100%;min-height:0;padding:2.5rem 3.375rem 2.5rem 4rem;display:flex;overflow:hidden auto}.learner-reader .course-identity{--print-rule-color:#23252385;--print-rule-right:0;--print-mask-x:-163px;--print-mask-y:-647px;padding-bottom:1.4rem}.course-identity-list{gap:.35rem;margin:0;display:grid}.course-identity-row{grid-template-columns:max-content minmax(0,1fr);align-items:baseline;gap:.5rem;display:grid}.course-identity-row dt{color:#5f605a;font:.8125rem / 1.5 var(--mono);letter-spacing:.03em;white-space:nowrap}.course-identity-row dd{color:#222421;overflow-wrap:anywhere;min-width:0;margin:0;font-size:1rem;font-weight:500;line-height:1.5}.course-identity-row .course-version-button{width:auto;color:inherit;cursor:pointer;font:inherit;background:0 0;border:0;justify-content:flex-start;align-items:baseline;padding:0;display:inline-flex;position:relative}.course-identity-row .course-version-button:hover{color:#175ed0}.course-identity-row .version-unseen-dot{background:#c84b31;width:.42rem;height:.42rem;position:absolute;top:-.05rem;right:-.48rem;box-shadow:0 0 0 2px #f3efe5}.course-identity-unlock{width:100%;margin-top:1.125rem}.learner-reader .learner-course-navigation{width:calc(100% + 1rem);margin-left:-1rem;padding-top:1.5rem}.learner-reader-stage{min-width:0;min-height:0;overflow:hidden}.learner-reader-stage .reader-document-grid{grid-template-columns:minmax(0,1fr);height:100%;display:grid}.learner-reader-stage .course-content{color:#222421;height:100%}.learner-reader-stage .course-content:has(>.body-content-transition>.content-transition-live>:is(.learner-access-gate,.learner-error-state--reading)){flex-direction:column;display:flex}.body-content-transition:has(>.content-transition-live>:is(.learner-access-gate,.learner-error-state--reading)){flex:1 0 auto;min-height:0;display:flex}.body-content-transition>.content-transition-live:has(>:is(.learner-access-gate,.learner-error-state--reading)){flex:1;place-items:center;display:grid}.body-content-transition>.content-transition-before>.content-transition-live:has(>:is(.learner-access-gate,.learner-error-state--reading)){place-items:center;height:100%;display:grid}.body-content-transition>.content-transition-live>.learner-error-state--reading{min-height:0}.learner-reader-stage .course-toc{display:none}@media (width<=90.625rem){.learner-reader.course-layout{grid-template-columns:15.625rem minmax(0,1fr)}.learner-reader .course-sidebar-scroll{padding-left:3rem;padding-right:2.625rem}}@media (width<=65.625rem){.learner-reader.course-layout{grid-template-columns:13.75rem minmax(0,1fr)}.learner-reader .course-sidebar-scroll{padding-left:2.625rem;padding-right:2rem}}@media (width<=47.5rem){:is(html:has(.learner-reader),body:has(.learner-reader)){height:100%;overflow:hidden}.learner-banner{min-height:3.625rem;padding:env(safe-area-inset-top) 1rem 0;position:sticky}.learner-brand{font-size:1.3125rem}.learner-reader.course-layout{width:min(100%,48rem);height:calc(100dvh - 3.625rem - 4.25rem - 3.625rem - env(safe-area-inset-top) - env(safe-area-inset-bottom));grid-template-rows:minmax(0,1fr);grid-template-columns:minmax(0,1fr);min-height:0;padding:0 1rem;overflow:hidden}.learner-reader .course-sidebar,.learner-reader .course-breadcrumb{display:none}.learner-reader-stage :is(h1,h2,h3,h4,[id]){scroll-margin-top:1rem}.learner-reader-stage,.learner-reader-stage .course-content{min-height:0}.learner-reader-stage,.learner-reader-stage .reader-document-grid,.learner-reader-stage .course-content{height:100%}.learner-reader-stage .course-content{overscroll-behavior:contain;padding-bottom:max(2rem, env(safe-area-inset-bottom));overflow:hidden auto}.learner-reader .course-chapter-pagination{display:none}}.course-route-loading{--course-loading-size:144px;pointer-events:none;place-items:center;display:grid;position:fixed;inset:0}@media (width<=47.5rem){.course-route-loading{--course-loading-size:112px}}.body-loading{--body-loading-size:144px;width:100%;height:var(--body-loading-height,65dvh);display:block;position:relative}.body-loading>.paper-motion{position:absolute;top:50%;left:50%;transform:translate(-50%,-50%)}.body-loading-label{clip-path:inset(50%);white-space:nowrap;width:1px;height:1px;position:absolute;overflow:hidden}.learner-reading-state:has(>.body-loading){max-width:none;min-height:0;padding-bottom:0;display:block}@media (width<=47.5rem){.body-loading{--body-loading-size:112px}}@keyframes learner-body-out{0%{opacity:1}to{opacity:0}}@keyframes learner-body-in{0%{opacity:0}to{opacity:1}}.content-transition{min-width:0;position:relative}.content-transition-live{min-width:0}.content-transition-before,.content-transition-loading{position:absolute;inset:0}.content-transition-before{pointer-events:none}.content-transition[data-transition-phase=leaving]>.content-transition-before,.content-transition[data-transition-phase=loading-out]>.content-transition-loading{animation:learner-body-out var(--transition-duration) ease-in both}.content-transition[data-transition-phase=entering]>.content-transition-live,.content-transition[data-transition-phase=loading-in]>.content-transition-loading{animation:learner-body-in var(--transition-duration) ease-out both}.page-content-transition,.page-content-transition>.content-transition-live{min-height:calc(100dvh - 60px)}.page-content-transition>.content-transition-loading{pointer-events:none;position:fixed;inset:0}.body-content-transition{min-height:65dvh}.body-content-transition>.content-transition-live>.course-page-content{margin-top:0}.list-content-transition{min-height:220px}.list-loading{place-items:center;min-height:220px;display:grid}.landing--home .list-content-transition,.landing--home .list-loading{min-height:0}@media (width<=47.5rem){body:has(.learner-app:not(.learner-app--authorization,.learner-app--reading)){height:100dvh;min-height:0;overflow:hidden}.learner-app:not(.learner-app--authorization,.learner-app--reading){flex-direction:column;height:100dvh;min-height:0;display:flex;overflow:hidden}.learner-app:not(.learner-app--authorization,.learner-app--reading) .learner-banner{flex:none}.learner-app:not(.learner-app--authorization,.learner-app--reading) .learner-page{min-height:0;margin-bottom:calc(4.25rem + env(safe-area-inset-bottom));overscroll-behavior:contain;flex:auto;padding-bottom:0;overflow:hidden auto}.learner-app--keyboard-open:not(.learner-app--authorization,.learner-app--reading) .learner-page{margin-bottom:0}.learner-app:not(.learner-app--authorization,.learner-app--reading) .page-content-transition{height:100%;min-height:0}.learner-app:not(.learner-app--authorization,.learner-app--reading) .page-content-transition>.content-transition-live,:is(.learner-app:not(.learner-app--authorization,.learner-app--reading) .landing:has(.list-content-transition),.learner-app:not(.learner-app--authorization,.learner-app--reading) .learner-account-page,.learner-app:not(.learner-app--authorization,.learner-app--reading) .learner-error-state--page){min-height:100%}.learner-app:not(.learner-app--authorization,.learner-app--reading) .landing:not(.landing--home){gap:16px;padding:24px 0 32px}.learner-app:not(.learner-app--authorization,.learner-app--reading) .learner-account-page{padding:24px 20px 32px}.landing-copy:not(.landing-copy--home),.section-title:not(.section-title--home),.learner-account-page>h1{clip-path:inset(50%);white-space:nowrap;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}}@media (prefers-reduced-motion:reduce){.content-transition[data-transition-phase]>.content-transition-before,.content-transition[data-transition-phase]>.content-transition-live,.content-transition[data-transition-phase]>.content-transition-loading{animation:none}}.content-transition-default-loading{place-items:center;min-height:220px;display:grid}