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#627cae;border-radius:9px;font-size:13px;color:#fff;line-height:1.6;text-align:center;cursor:pointer}.study-button:hover{background:#536e9f}.study-button.secondary{background:#f5f8fd;color:#526e9a;border-color:#d8e1ef}.study-button.secondary:hover{background:#eaf0fa}.study-button.danger{background:#fff5f5;color:#b95864;border-color:#ecd1d5}.study-button:disabled,.study-option:disabled{opacity:.55;cursor:wait}.study-text-button{font-size:12px;line-height:1.8;color:#6681ad;background:transparent;padding:4px 0;cursor:pointer}.study-actions{display:flex;flex-wrap:wrap;gap:11px;align-items:center;margin:17px 0}.study-options,.study-children{display:flex;flex-wrap:wrap;gap:9px;margin:15px 0 24px}.study-option{border:1px solid #dce4f0;border-radius:9px;background:#f5f7fc;color:#6c7f9e;padding:9px 16px;font-size:13px;line-height:1.6}.study-option[aria-pressed=true]{background:#637cad;color:#fff;border-color:#637cad}.study-field{display:flex;flex-direction:column;gap:7px;margin:15px 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#dfe6f1;border-radius:13px;display:flex;flex-direction:column;align-items:flex-start;gap:4px}.study-stat>span{font-size:12px;color:#7a8da9}.study-stat>strong{font-family:Georgia,var(--sans);font-size:32px;font-weight:500;color:#546d9c;line-height:1.7}.study-stat>small{font-size:11px;color:#93a0b5}.study-section{margin-top:30px}.study-section h2,.study-section-heading h2{font-family:var(--serif);font-size:21px;color:#435a7e;margin:0}.study-section-heading{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:18px}.study-empty{display:flex;align-items:center;flex-direction:column;text-align:center;background:#fff;border:1px solid #dfe6f2;padding:43px 23px;border-radius:15px}.study-empty-symbol{font-size:42px;color:#b6c5dd;line-height:1.4}.study-empty h2{font-size:20px;margin:15px 0 8px}.study-empty p{color:#8797b0;font-size:13px;max-width:520px}.study-tag{display:inline-flex;align-items:center;background:#edf2fa;border:1px solid #e3eaf5;color:#6f86ad;font-size:11px;line-height:1.6;padding:3px 8px;border-radius:5px}.study-status{font-size:11px;color:#9a8b72;background:#f5f0e7;padding:3px 9px;border-radius:5px}.study-status.green{color:#54826d;background:#edf7f1}.study-status.red{color:#b56570;background:#fff1f3}.study-child-row{display:flex;align-items:center;gap:12px;margin:10px 0 22px}.study-avatar{display:flex;align-items:center;justify-content:center;width:38px;height:38px;background:#e2eaf7;border:1px solid #cddaf0;border-radius:50%;font-family:var(--serif);font-size:17px;color:#738cb6}.study-child-row select{background:transparent;border:0;font-size:16px;padding-left:0}.study-child-row .study-text-button{margin-left:auto}.study-home-hero{position:relative;overflow:hidden;isolation:isolate;background:#e7edf8;border:1px solid #e4ebf7;border-radius:18px;min-height:295px;padding:32px 36px}.study-home-hero>img{position:absolute;inset:0;z-index:-2;width:100%;height:100%;object-fit:cover;object-position:70% center;opacity:.85}.study-home-hero:after{content:'';position:absolute;inset:0;z-index:-1;background:linear-gradient(90deg,#e7edf8 15%,#e7edf8e6 40%,#e7edf820 80%)}.study-home-hero h2{font-family:var(--serif);font-size:31px;font-weight:500;letter-spacing:2px;line-height:1.7;white-space:pre-line;color:#425b7f;margin:12px 0}.study-home-hero p{white-space:pre-line;color:#7489ac;font-size:13px;line-height:1.9}.study-shortcuts{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:13px;margin:22px 0}.study-shortcut{background:#ffffffa8;border:1px solid #dfe7f3;border-radius:11px;padding:19px 16px;color:#6d85af;font-size:13px;text-align:center}.study-shortcut:hover{background:#fff;border-color:#bdcee7}.study-item-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:17px;margin:20px 0}.study-item-tile{border:1px solid #dfe6f2;background:#fff;border-radius:13px;padding:20px;display:block;min-width:0;transition:box-shadow .2s}.study-item-tile:hover{box-shadow:0 8px 25px #56709c10}.study-item-meta{display:flex;gap:9px;align-items:center;flex-wrap:wrap;font-size:11px;color:#8798b2;margin-bottom:15px}.study-item-meta .study-status{margin-left:auto}.study-item-tile .study-math{display:-webkit-box;-webkit-line-clamp:3;-webkit-box-orient:vertical;overflow:hidden;min-height:65px;max-height:110px;font-size:15px}.study-item-tile>img{width:100%;height:110px;object-fit:contain;object-position:left top;margin-top:13px;background:#fafbfe}.study-item-footer{border-top:1px solid #ecf0f7;margin-top:15px;padding-top:12px;display:flex;justify-content:space-between;gap:10px;font-size:10px;color:#889ab4}.study-session-list{display:flex;flex-direction:column;gap:8px;margin-top:17px}.study-session-link{padding:15px 18px;background:#fff;border:1px solid #dfe6f2;border-radius:8px;font-size:13px;color:#6981a8}.study-math{white-space:pre-wrap;overflow-wrap:anywhere;line-height:1.95}.study-math 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summary{cursor:pointer;color:#6680ac;font-size:13px}.study-answer>.study-math{margin-top:13px}.study-check{display:flex;align-items:center;gap:9px;margin:13px 0}.study-check input{width:17px;height:17px;accent-color:#6d85b3}.study-report-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:20px}.study-report-grid>.study-panel{margin:0}.study-bar-row{display:grid;grid-template-columns:115px minmax(40px,1fr) 45px;align-items:center;gap:14px;margin:18px 0;font-size:12px;color:#7b8da9}.study-bar-track{height:7px;border-radius:8px;background:#ecf1f8;overflow:hidden}.study-bar{display:block;height:100%;background:#96acd0;border-radius:8px}.study-bar-row strong{text-align:right;font-weight:400;font-size:11px}.study-trend-row{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin:17px 0;color:#7f90a9;font-size:12px}.study-dialog{width:min(620px,calc(100vw - 30px));max-height:90vh;overflow:auto;border:1px solid #d7e0ef;padding:26px;border-radius:16px;color:#455b7b;background:#fcfdff;box-shadow:0 20px 80px #273e6b35;font-size:14px}.study-dialog::backdrop{background:#24375666;backdrop-filter:blur(4px)}.study-dialog-top{display:flex;justify-content:space-between;gap:20px;align-items:center;margin-bottom:15px}.study-dialog-top h2{font-size:20px;margin:0}.study-dialog code{font-size:12px;white-space:pre-wrap;overflow-wrap:anywhere;background:#eef3fb;padding:10px;border-radius:5px;display:block;color:#677fa9}.study-config-section{margin:22px 0}.study-login-layout{display:grid;grid-template-columns:1fr 1fr;gap:30px;margin:15px 0 30px;min-height:580px}.study-login-intro{position:relative;overflow:hidden;isolation:isolate;border-radius:16px;background:#e6edf7;padding:50px 35px}.study-login-intro>img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;object-position:60% center;opacity:.52;z-index:-2}.study-login-intro:after{content:'';position:absolute;inset:0;z-index:-1;background:linear-gradient(#e7eef9d0,#e7eef91a 70%)}.study-login-intro h1{white-space:pre-line;font-family:var(--serif);font-size:32px;font-weight:500;line-height:1.9;letter-spacing:2px;color:#536e97;margin:25px 0}.study-login-intro p{font-size:13px;color:#768eb2;max-width:240px;line-height:2}.study-login-panel{margin:0;padding:33px;align-self:center}.study-login-panel>.study-options{margin-top:23px}.study-code-row{display:flex;align-items:center;gap:10px}.study-code-row>.study-field{flex:1;min-width:0}.study-code-row>button{white-space:nowrap;margin-top:24px;padding-left:12px;padding-right:12px;font-size:12px}.study-login-extra{display:flex;flex-wrap:wrap;gap:18px;justify-content:space-between;align-items:center;margin-top:20px}.study-wechat-mark{background:#e3f3ea;color:#5c9878;width:80px;height:80px;border-radius:20px;display:flex;align-items:center;justify-content:center;font-size:25px;margin:30px auto 18px}.study-login-panel h3{text-align:center}.video-qa-panel{margin-top:25px}.video-qa-context{background:#f7f9fd;border:1px solid #dfe7f2;border-radius:9px;padding:14px 17px;margin:15px 0}.video-qa-context summary{color:#6d84ad;cursor:pointer;font-size:13px}.video-qa-messages{display:flex;flex-direction:column;gap:12px;margin-top:22px}.video-qa-question,.video-qa-answer{border:1px solid #e0e8f3;border-radius:10px;padding:17px;background:#fafbfe}.video-qa-question{background:#edf3fc;margin-left:30px}.video-qa-answer{margin-right:25px}.video-qa-messages p{margin:10px 0 0;font-size:14px}.video-qa-answer .study-math{margin:12px 0;font-size:14px}.video-qa-answer small{font-size:11px}.study-mobile-nav{display:none}.topbar-account{display:flex;align-items:center;gap:8px;background:#e8eef9;color:#6f87af;border:1px solid #d9e3f3;border-radius:22px;padding:6px 12px;font-size:11px;letter-spacing:0}.topbar-account .study-avatar{width:24px;height:24px;font-size:11px}.side-nav .nav-item{font-size:13px}.sidebar{padding-top:30px}.sidebar-divider{margin-top:26px;margin-bottom:25px}.sidebar .side-note{margin-bottom:30px;padding-top:25px}.sidebar .side-note p{font-size:18px}.nav-caption{font-size:11px}.study-view[aria-busy=true]{opacity:.8}.study-unavailable{min-height:300px;padding:35px;text-align:center}.study-unavailable h2{font-size:24px}.study-unavailable p{color:#7e90ad}.study-footer-hint{font-size:11px;color:#8a9bb4;margin:25px 0;text-align:center}
@media(min-width:1600px){.study-home-hero{min-height:325px;padding:38px 42px}.study-home-hero h2{font-size:37px}.study-view{font-size:15px}.study-item-tile .study-math{font-size:17px}}
@media(max-width:1100px){.study-stats{grid-template-columns:repeat(2,minmax(0,1fr))}.study-shortcuts{grid-template-columns:repeat(2,minmax(0,1fr))}.study-login-layout{gap:20px;grid-template-columns:.8fr 1.2fr}.study-login-intro{padding:40px 25px}.study-login-intro h1{font-size:27px}.study-login-panel{padding:25px}}
@media(max-width:700px){.study-view{font-size:13px;padding-bottom:20px}.study-heading{margin-bottom:20px}.study-heading h1{font-size:25px}.study-subtitle{font-size:12px}.study-eyebrow{font-size:9px}.study-panel{padding:20px;border-radius:12px}.study-panel h2{font-size:17px}.study-home-hero{min-height:300px;padding:25px}.study-home-hero h2{font-size:28px;letter-spacing:1px}.study-home-hero p{font-size:11px;max-width:245px}.study-home-hero .study-actions{gap:8px}.study-home-hero .study-button{font-size:11px;padding:9px 12px;min-height:39px}.study-stats{gap:11px;margin:19px 0}.study-stat{padding:16px 19px}.study-stat>strong{font-size:29px}.study-stat>span{font-size:11px}.study-stat>small{font-size:10px}.study-shortcuts{gap:10px}.study-shortcut{font-size:12px;padding:17px 10px}.study-item-grid,.study-report-grid{grid-template-columns:1fr;gap:13px}.study-item-tile{padding:17px}.study-section-heading h2{font-size:19px}.study-item-meta{font-size:10px}.study-child-row select{font-size:14px}.study-button{font-size:12px;padding:10px 15px}.study-options{gap:7px}.study-option{font-size:12px;padding:9px 13px}.study-login-layout{display:block;margin-top:0;min-height:0}.study-login-intro{min-height:185px;padding:25px;margin-bottom:20px}.study-login-intro h1{font-size:26px;line-height:1.6;margin:10px 0}.study-login-intro p{font-size:11px;max-width:220px}.study-login-intro>.study-eyebrow{font-size:8px}.study-login-panel{padding:22px}.study-code-row{gap:7px}.study-code-row>button{font-size:11px;padding:9px;min-height:42px}.study-login-panel>.study-options{margin-bottom:14px}.study-field{font-size:12px}.study-notice{font-size:11px;padding:11px 13px}.study-trend-row{font-size:11px;gap:5px}.study-bar-row{grid-template-columns:90px minmax(30px,1fr) 38px;gap:10px;font-size:11px}.study-dialog{padding:22px}.video-qa-panel h2{font-size:18px}.study-mobile-nav{position:fixed;bottom:0;left:0;right:0;z-index:35;display:flex;justify-content:space-around;align-items:center;background:#fbfdfff5;backdrop-filter:blur(12px);border-top:1px solid #dfe7f2;padding:8px 10px calc(8px + env(safe-area-inset-bottom))}.study-mobile-nav a{display:flex;align-items:center;flex-direction:column;gap:1px;min-width:45px;padding:3px 9px;color:#93a0b7;font-size:10px}.study-mobile-nav a>span:first-child{font-size:20px;line-height:1.3}.study-mobile-nav a.active{color:#607aaa}.site-footer{padding-bottom:95px}.topbar-account{font-size:10px;padding:5px 9px}.topbar-account .study-avatar{width:20px;height:20px;font-size:10px}.topbar-right{gap:5px}.topbar-labs-link{display:none}.mobile-save{display:none}.toast{bottom:85px}.study-feedback{bottom:85px}}
@media(prefers-reduced-motion:reduce){.study-view *{scroll-behavior:auto!important}}
.library-source-controls{display:flex;align-items:center;gap:16px}.library-source-controls .text-button{white-space:nowrap}.library-source-controls .text-button:disabled{opacity:.5;cursor:wait}
@media(max-width:700px){.library-source-controls{justify-content:space-between;gap:10px;margin-top:10px}.library-source-controls .catalogue-count{margin-top:0}}

.video-qa-preview {
  display: flex;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 12px;
  margin: 0 0 16px;
}
.video-qa-preview img {
  max-width: min(100%, 360px);
  max-height: 200px;
  object-fit: contain;
  border: 1px solid #dfe7f2;
  border-radius: 8px;
}