:root{--ink:#102d67;--text:#2b3d5d;--muted:#74839b;--line:rgba(103,130,174,.2);--blue:#367fe8;--blue-soft:#edf5ff;--surface:rgba(255,255,255,.84);--shadow:0 18px 50px rgba(62,89,130,.1);--page:1290px}*{box-sizing:border-box}html{scroll-behavior:smooth}body{min-height:100vh;margin:0;color:var(--text);font-family:Inter,"PingFang SC","Microsoft YaHei",sans-serif;background:radial-gradient(circle at 4% 7%,rgba(255,211,221,.5),transparent 27%),radial-gradient(circle at 96% 8%,rgba(195,239,232,.48),transparent 29%),linear-gradient(135deg,#fff9fb,#f7fbff 54%,#f4fcfa);background-attachment:fixed}button,input,select,textarea{font:inherit}button,a,select{cursor:pointer}a{color:inherit;text-decoration:none}svg{width:21px;height:21px;fill:none;stroke:currentColor;stroke-width:1.8;stroke-linecap:round;stroke-linejoin:round}.svg-sprite{position:absolute;width:0;height:0}.is-hidden,[hidden]{display:none!important}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:3px solid rgba(54,127,232,.28);outline-offset:3px}
.site-header{position:relative;z-index:50;padding:22px 24px 0}.capsule-nav{display:grid;grid-template-columns:1fr auto 1fr;width:min(var(--page),100%);min-height:76px;margin:auto;padding:8px 14px 8px 28px;align-items:center;border:1px solid rgba(255,255,255,.84);border-radius:999px;background:rgba(255,255,255,.74);box-shadow:0 12px 40px rgba(54,77,114,.1);backdrop-filter:blur(20px)}.brand{width:max-content;color:var(--ink);font-family:"Trebuchet MS",sans-serif;font-size:25px;font-weight:300;letter-spacing:-2px}.brand span{color:#5677a8}.desktop-nav{display:flex;gap:14px}.desktop-nav a{display:grid;min-width:70px;min-height:48px;padding:0 18px;place-items:center;border-radius:999px;font-weight:600;transition:.2s}.desktop-nav a:hover{background:#eef3fb}.desktop-nav .active{color:#fff;background:var(--ink);box-shadow:0 8px 20px rgba(16,45,103,.2)}.header-actions{position:relative;display:flex;justify-content:flex-end;align-items:center}.login-button,.avatar-button,.mobile-menu-button{display:grid;width:52px;height:52px;padding:0;place-items:center;border:1px solid #92a2bd;border-radius:50%;color:var(--ink);background:#fff;font-size:14px;font-weight:700}.avatar-button{padding:4px;border-color:rgba(255,255,255,.8)}.avatar-button span{display:grid;width:100%;height:100%;place-items:center;border-radius:50%;color:#fff;background:linear-gradient(145deg,#456f9c,#d9a17b);font-size:20px}.mobile-menu-button{display:none}.profile-menu{position:absolute;z-index:70;top:62px;right:0;width:215px;padding:9px;border:1px solid var(--line);border-radius:16px;background:#fff;box-shadow:0 18px 50px rgba(30,53,90,.18);opacity:0;visibility:hidden;transform:translateY(-6px);transition:.2s}.profile-menu.open{opacity:1;visibility:visible;transform:none}.profile-menu>strong{display:block;padding:11px 12px;border-bottom:1px solid var(--line);color:var(--ink)}.profile-menu a,.profile-menu button{display:flex;width:100%;min-height:44px;align-items:center;gap:10px;padding:0 12px;border:0;border-radius:10px;background:transparent;text-align:left}.profile-menu a:hover,.profile-menu button:hover{background:#f2f6fc}.profile-menu button{color:#bd4747}.mobile-menu{display:none}
.learning-page{width:min(var(--page),calc(100% - 48px));margin:42px auto 60px}.learning-heading{display:flex;min-height:126px;align-items:center;justify-content:space-between;padding:0 16px}.eyebrow,.course-panel header span,.notebook-panel header div>span{margin:0;color:#4c89df;font-size:10px;font-weight:800;letter-spacing:.18em}.learning-heading h1{margin:8px 0 7px;color:var(--ink);font-size:42px;letter-spacing:.04em}.learning-heading>div>p:last-child{margin:0;color:#6e7d95;font-size:15px}.today-summary{display:flex;align-items:baseline;gap:9px;color:#536783}.today-summary strong{color:var(--ink);font-size:52px;line-height:1}.today-summary small{font-size:14px}.learning-workspace{display:grid;grid-template-columns:300px minmax(0,1fr) 320px;gap:14px;align-items:stretch}.panel{min-width:0;overflow:hidden;border:1px solid rgba(255,255,255,.92);border-radius:22px;background:var(--surface);box-shadow:var(--shadow);backdrop-filter:blur(18px)}
.course-panel{display:flex;min-height:690px;flex-direction:column;padding:24px 16px}.course-panel>header,.notebook-panel>header{display:flex;align-items:flex-start;justify-content:space-between;gap:10px;padding:0 5px 17px;border-bottom:1px solid var(--line)}.course-panel h2,.notebook-panel h2{margin:5px 0 0;color:var(--ink);font-size:20px}.course-panel header>small{padding:5px 8px;border-radius:99px;color:#4476b9;background:#edf4fd;font-size:10px}.subject-select{display:grid;gap:7px;padding:17px 4px 12px;color:#718099;font-size:10px;font-weight:800;letter-spacing:.05em}.subject-select select{width:100%;height:46px;padding:0 38px 0 12px;border:1px solid #dce5f0;border-radius:11px;outline:0;color:#294567;background:#fff;font-size:13px;font-weight:700}.catalog-path{margin:0 4px 11px;padding:9px 10px;border-radius:9px;color:#5d7495;background:#f3f7fc;font-size:10px;line-height:1.45}.course-tree{min-height:0;overflow:auto;padding:0 2px 8px;scrollbar-width:thin}.tree-group{margin:3px 0}.tree-toggle{display:flex;width:100%;min-height:41px;align-items:center;gap:8px;padding:0 9px;border:0;border-radius:9px;color:#435a7a;background:transparent;text-align:left;font-size:12px;font-weight:700}.tree-toggle:hover,.tree-group.open>.tree-toggle{color:#1f5fae;background:#edf5ff}.tree-toggle svg{width:15px;transition:.2s}.tree-group.open>.tree-toggle svg{transform:rotate(90deg)}.tree-children{display:none;margin-left:12px;padding-left:7px;border-left:1px solid #dce6f2}.tree-group.open>.tree-children{display:block}.tree-video{display:block;width:100%;min-height:58px;margin:4px 0;padding:9px 9px 8px;border:1px solid transparent;border-radius:10px;color:#556983;background:transparent;text-align:left}.tree-video strong,.tree-video small{display:block}.tree-video strong{overflow:hidden;color:#29466d;font-size:12px;text-overflow:ellipsis;white-space:nowrap}.tree-video small{margin-top:6px;color:#8795a8;font-size:10px}.tree-video .mini-progress{display:block;height:3px;margin-top:7px;overflow:hidden;border-radius:99px;background:#e4ebf4}.tree-video .mini-progress i{display:block;height:100%;border-radius:inherit;background:var(--blue)}.tree-video:hover,.tree-video.active{border-color:#8fb5e8;background:#f1f7ff;box-shadow:0 7px 18px rgba(54,127,232,.08)}.tree-video.active{box-shadow:inset 3px 0 var(--blue)}.loading-state{padding:48px 12px;color:var(--muted);font-size:12px;text-align:center}
.video-panel{display:flex;min-height:690px;flex-direction:column;padding:12px}.video-wrap{position:relative;overflow:hidden;aspect-ratio:16/9;border-radius:15px;background:#071d48}.video-wrap video{display:block;width:100%;height:100%;background:#071d48}.video-empty{display:grid;position:absolute;inset:0;place-content:center;justify-items:center;gap:9px;color:rgba(255,255,255,.76);background:radial-gradient(circle at 80% 20%,rgba(54,127,232,.28),transparent 35%),linear-gradient(145deg,#0b2d68,#071b43)}.video-empty svg{width:56px;height:56px;padding:13px;border:1px solid rgba(255,255,255,.55);border-radius:50%;color:#fff}.video-empty strong{font-size:16px}.video-empty span{font-size:11px;opacity:.72}.video-copy{display:flex;flex:1;flex-direction:column;padding:22px 12px 10px}.video-title-row{display:flex;align-items:flex-start;justify-content:space-between;gap:14px}.video-title-row h2{margin:9px 0 0;color:var(--ink);font-size:23px}.status-pill{display:inline-flex;padding:5px 9px;border-radius:99px;color:#2c6fc9;background:#eaf3ff;font-size:10px;font-weight:800}.restart-button{min-height:42px;padding:0 14px;border:1px solid #b9c7da;border-radius:10px;color:#294c7d;background:#fff;font-weight:700}.restart-button:disabled{cursor:not-allowed;opacity:.45}.video-copy>p{min-height:44px;margin:13px 0 12px;color:#74839a;font-size:12px;line-height:1.7}.lesson-progress{margin-top:auto;padding-top:17px;border-top:1px solid var(--line)}.lesson-progress>div:first-child{display:flex;align-items:baseline;gap:9px}.lesson-progress span{color:#52657f;font-size:12px}.lesson-progress strong{color:var(--blue);font-size:24px}.lesson-progress small{margin-left:auto;color:#7f8ba0;font-size:11px}.progress-track{height:8px;margin-top:11px;overflow:hidden;border-radius:99px;background:#e5edf8}.progress-track span{display:block;width:0;height:100%;border-radius:inherit;background:var(--blue);transition:width .25s}
.notebook-panel{display:flex;min-height:690px;flex-direction:column;padding:24px 18px}.save-status{max-width:115px;color:#7c899b;font-size:9px;line-height:1.4;text-align:right}.note-paper{display:flex;min-height:390px;flex:1;flex-direction:column;margin-top:17px;padding:17px;border:1px solid #dfe7f1;border-radius:14px;background:repeating-linear-gradient(#fff,#fff 30px,#edf2f8 31px)}.note-paper label{display:grid;gap:6px;color:#74839a;font-size:10px;font-weight:700}.note-paper input,.note-paper textarea{width:100%;border:0;outline:0;color:#2a456a;background:transparent}.note-paper input{height:42px;padding:0 2px;border-bottom:1px solid #dfe7f1;font-size:14px;font-weight:800}.note-content-label{min-height:0;flex:1;margin-top:14px}.note-paper textarea{height:100%;min-height:280px;padding:5px 2px;resize:none;font-size:13px;line-height:31px}.note-paper input:disabled,.note-paper textarea:disabled{cursor:not-allowed}.save-note{display:flex;min-height:48px;align-items:center;justify-content:center;gap:8px;margin-top:12px;border:0;border-radius:11px;color:#fff;background:var(--ink);font-weight:800}.save-note:disabled{cursor:not-allowed;opacity:.45}.notebook-helper{display:flex;gap:8px;margin:13px 2px;color:#71819a;font-size:10px;line-height:1.55}.notebook-helper svg{width:16px;flex:0 0 16px;color:#4a80c6}.study-stats{display:grid;grid-template-columns:1fr 1fr;gap:8px;margin-top:auto}.study-stats>div{padding:12px;border:1px solid #dfe7f1;border-radius:11px;background:rgba(255,255,255,.75)}.study-stats span,.study-stats small{color:#7d8a9e;font-size:9px}.study-stats strong{display:inline-block;margin:5px 4px 0 0;color:var(--ink);font-size:21px}.toast{position:fixed;z-index:120;left:50%;bottom:25px;padding:11px 18px;border-radius:99px;color:#fff;background:var(--ink);opacity:0;pointer-events:none;transform:translate(-50%,12px);transition:.2s}.toast.show{opacity:1;transform:translate(-50%,0)}
@media(max-width:1120px){.learning-workspace{grid-template-columns:280px minmax(0,1fr)}.notebook-panel{grid-column:1/-1;min-height:520px}.note-paper{min-height:300px}.note-paper textarea{min-height:190px}.study-stats{margin-top:14px}}
@media(max-width:900px){.site-header{padding:10px 14px 0}.capsule-nav{display:flex;min-height:62px;padding:7px 8px 7px 18px;border-radius:18px;justify-content:space-between}.desktop-nav,.login-button,.avatar-button{display:none!important}.mobile-menu-button{display:grid;width:44px;height:44px;border:0}.mobile-menu{position:absolute;top:80px;right:14px;left:14px;grid-template-columns:repeat(2,1fr);gap:8px;padding:12px;border:1px solid var(--line);border-radius:16px;background:#fff;box-shadow:var(--shadow)}.mobile-menu:not([hidden]){display:grid}.mobile-menu a{display:grid;min-height:48px;place-items:center;border-radius:10px;background:#f4f7fb;font-weight:700}.mobile-menu a.active{color:#fff;background:var(--ink)}.learning-page{width:100%;margin:25px 0 0}.learning-heading{padding:0 20px}.learning-heading h1{font-size:34px}.today-summary strong{font-size:40px}.learning-workspace{display:block}.panel{border-radius:0}.course-panel{min-height:auto;margin-bottom:12px}.course-tree{max-height:420px}.video-panel{min-height:auto;margin-bottom:12px}.notebook-panel{min-height:520px}}
@media(max-width:520px){.learning-heading{min-height:150px;align-items:flex-start;flex-direction:column;padding:18px}.today-summary{align-self:flex-end;margin-top:-42px}.learning-heading h1{font-size:31px}.learning-heading>div>p:last-child{font-size:13px}.video-panel{padding:8px}.video-copy{padding:18px 8px 8px}.video-title-row{flex-direction:column}.restart-button{align-self:flex-end}.lesson-progress>div:first-child{flex-wrap:wrap}.lesson-progress small{width:100%;margin-left:0}.course-panel,.notebook-panel{padding-inline:14px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}

.link-note-time{display:flex;width:100%;min-height:42px;align-items:center;justify-content:space-between;margin-top:12px;padding:0 14px;border:1px solid #c8d8ec;border-radius:11px;color:#315f9f;background:#f2f7fd;font-size:11px;font-weight:700}.link-note-time span{font-variant-numeric:tabular-nums}.link-note-time:disabled{cursor:not-allowed;opacity:.45}

/* Match the shared avatar hover card used by Documents and Space. */
.avatar-button{box-shadow:0 4px 15px rgba(24,49,91,.18)}.avatar-button span{overflow:hidden}.avatar-button img{width:100%;height:100%;object-fit:cover;border-radius:50%}.profile-menu{width:210px;padding:8px}.profile-menu:before{position:absolute;right:0;bottom:100%;width:70px;height:12px;content:""}.profile-menu.open,.avatar-button:not(.is-hidden):hover+.profile-menu,.profile-menu:hover{opacity:1;visibility:visible;transform:none}.profile-summary{display:flex;align-items:center;gap:10px;margin:2px 4px 7px;padding:8px;border-bottom:1px solid var(--line)}.profile-summary span{display:grid;width:34px;height:34px;flex:0 0 34px;place-items:center;overflow:hidden;border-radius:50%;color:#fff;background:linear-gradient(145deg,#456f9c,#d9a17b);font-weight:700}.profile-summary span img{width:100%;height:100%;object-fit:cover}.profile-summary strong{min-width:0;overflow:hidden;color:var(--ink);font-size:14px;text-overflow:ellipsis;white-space:nowrap}.profile-menu a,.profile-menu button{gap:11px;color:var(--text)}.profile-menu button{margin-top:5px;border-top:1px solid var(--line);border-radius:0 0 10px 10px}.profile-menu svg{width:19px}
@media(max-width:900px){.profile-menu{display:none!important}}