*{box-sizing:border-box}
body{margin:0;background:#f5f7fb;color:#172033;font-family:-apple-system,BlinkMacSystemFont,'Apple SD Gothic Neo',sans-serif}
header{height:66px;background:#fff;border-bottom:1px solid #e5e9f0;display:flex;align-items:center;gap:14px;padding:0 20px;position:sticky;top:0;z-index:20}
header b{color:#2457d6;letter-spacing:.03em}
main{max-width:1080px;margin:auto;padding:24px 16px 64px}
.card,.problem{background:#fff;border:1px solid #e5e9f0;border-radius:18px;padding:18px;margin-bottom:12px}
.hero{background:linear-gradient(135deg,#fff,#eef4ff)}
input{width:100%;padding:11px;border:1px solid #d8dee8;border-radius:10px;margin:5px 0 10px}
.btn{border:0;border-radius:10px;padding:10px 13px;font-weight:800;cursor:pointer}
.btn:disabled{opacity:.55;cursor:wait}
.primary{background:#2457d6;color:#fff}.soft{background:#eef4ff;color:#2457d6}.danger{background:#fff0f0;color:#c33}.ok{background:#eaf8ee;color:#187a38}.review-on{background:#fff7df;color:#9a6300}
.row{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.problem img,.solution img{width:100%;max-height:680px;object-fit:contain}
.muted{color:#667085}.hidden{display:none}.solution{border-top:1px solid #eee;margin-top:12px;padding-top:12px}
.dashboard{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px;margin:14px 0 20px}
.stat{background:#fff;border:1px solid #e5e9f0;border-radius:16px;padding:14px}
.stat strong{display:block;font-size:24px;margin-top:4px}
.tabs{display:flex;gap:8px;overflow:auto;padding:4px 0 12px;position:sticky;top:66px;background:#f5f7fb;z-index:15}
.tabbtn{white-space:nowrap}.tabbtn.active{background:#2457d6;color:#fff}
.section-title{display:flex;align-items:center;justify-content:space-between;gap:10px;margin:22px 2px 10px}
.badge{display:inline-block;border-radius:999px;padding:4px 8px;font-size:12px;font-weight:800;background:#eef4ff;color:#2457d6}
.state-line{font-size:13px;margin-top:8px}
.state-q{color:#c33;font-weight:800}.state-r{color:#9a6300;font-weight:800}.state-u{color:#187a38;font-weight:800}
.grade-correct{background:#eaf8ee;color:#187a38}.grade-wrong{background:#fff0f0;color:#c33}.grade-ungraded{background:#eef1f5;color:#667085}
.answer-box{margin-top:10px;padding:10px;border:1px solid #e5e9f0;border-radius:12px;background:#fafbfc}.answer-inline{display:grid;grid-template-columns:minmax(100px,220px) auto;gap:8px;align-items:center}.answer-inline input{margin:0}
.board-grid{display:grid;gap:10px}.board-item{background:#fff;border:1px solid #e5e9f0;border-radius:16px;padding:15px;cursor:pointer}.board-item:hover{border-color:#9db7ee;box-shadow:0 2px 10px rgba(36,87,214,.08)}.board-item.hot{border-color:#f0b2b2;background:#fffafa}.board-count{font-size:26px;font-weight:950;color:#c33}.board-students{color:#667085;font-size:13px;margin-top:5px}
.board-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:10px}
.board-resolved{opacity:.68;background:#f7f8fa;border-color:#d8dde6}
.board-resolved .board-count{color:#667085}
.board-status{font-size:12px;font-weight:800;margin-top:6px}
.board-status.done{color:#187a38}
.board-filter-row{display:flex;gap:8px;align-items:center;flex-wrap:wrap;margin:12px 0}
.board-filter-row .btn{min-width:90px}.learning-resource-editor{margin-top:10px;border-top:1px solid #edf0f4;padding-top:10px}.learning-resource-card{border:1px solid #e5e9f0;border-radius:12px;padding:10px;margin:8px 0;background:#fff}.resource-row{padding:9px 2px;border-top:1px solid #edf0f4}.resource-row:first-child{border-top:0}.resource-head{display:flex;align-items:center;gap:8px;flex-wrap:wrap}.resource-kind{display:inline-flex;align-items:center;padding:3px 7px;border-radius:999px;background:#f1f5fb;color:#475467;font-size:11px;font-weight:700}.resource-title-link{color:#2457d6;font-weight:700;text-decoration:none;line-height:1.35}.resource-title-link:hover{text-decoration:underline}.resource-title-plain{font-weight:700;color:#172033}.resource-note{margin-top:4px;padding-left:2px}.class-resource-list{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.class-resource-card{background:#fff;border:1px solid #e5e9f0;border-radius:14px;padding:13px}.class-resources{margin:14px 0 20px}@media(max-width:760px){.class-resource-list{grid-template-columns:1fr}}.session-summary{margin:12px 0;padding:14px;border:1px solid #dfe5ef;border-radius:14px;background:#fff}.session-summary-grid{display:grid;grid-template-columns:repeat(6,minmax(90px,1fr));gap:8px;margin-top:10px}.session-metric{padding:9px;border-radius:10px;background:#f7f9fc;text-align:center}.session-metric b{display:block;font-size:20px}.session-history{margin-top:10px;font-size:12px;color:#667085}@media(max-width:900px){.session-summary-grid{grid-template-columns:repeat(2,1fr)}}.board-hint{font-size:12px;color:#2457d6;margin-top:8px}.board-detail{margin-top:12px;border-top:1px solid #edf0f4;padding-top:14px;cursor:default}.board-detail-grid{display:grid;grid-template-columns:minmax(0,45fr) minmax(0,55fr);gap:16px;align-items:start}.board-problem{position:sticky;top:78px;background:#fafbfc;border:1px solid #e5e9f0;border-radius:14px;padding:12px}.board-problem img,.board-solution img{width:100%;height:auto;object-fit:contain;border-radius:8px}.board-solution{background:#fff;border:1px solid #e5e9f0;border-radius:14px;padding:12px}.board-method{padding:10px 0;border-top:1px solid #edf0f4}.board-method:first-child{border-top:0}.board-method h4{margin:0 0 8px}.board-tabs{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:10px}.board-empty{padding:14px;border:1px dashed #ccd3dd;border-radius:12px;color:#667085}@media(max-width:900px){.board-detail-grid{grid-template-columns:1fr}.board-problem{position:static}}
.solution-shell{margin-top:14px;border-top:1px solid #e9edf3;padding-top:12px}
.solution-tabs{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:10px}
.solution-tab.active{background:#172033;color:#fff}
.solution-pane{display:none}.solution-pane.active{display:block}
.solution-split{display:grid;grid-template-columns:minmax(240px,.9fr) minmax(0,1.1fr);gap:18px;align-items:start}
.solution-problem-ref,.solution-body{background:#fafbfc;border:1px solid #e7ebf0;border-radius:14px;padding:12px}.solution-problem-ref{position:sticky;top:12px;align-self:start;max-height:calc(100vh - 28px);overflow:auto}
.solution-full .solution-body{width:100%}
.solution-method{margin-bottom:16px}
.solution-method h4{margin:2px 0 8px}
.video-link{display:block;padding:10px 12px;border-radius:10px;background:#eef4ff;color:#2457d6;text-decoration:none;font-weight:800;margin:6px 0}
.empty{padding:20px;text-align:center;color:#667085;background:#fff;border:1px dashed #d8dee8;border-radius:14px}

.todo-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin:10px 0 18px}
.todo{background:#fff;border:1px solid #e5e9f0;border-radius:16px;padding:14px}
.todo strong{display:block;font-size:20px;margin-top:4px}
.assignment-summary{background:#fff;border:1px solid #e5e9f0;border-radius:16px;padding:15px;margin:10px 0}
.assignment-head{display:flex;justify-content:space-between;gap:12px;align-items:center}
.progress-track{height:9px;background:#edf0f5;border-radius:99px;overflow:hidden;margin:10px 0 7px}
.progress-fill{height:100%;background:#2457d6;border-radius:99px}
.assignment-meta{display:flex;gap:10px;flex-wrap:wrap;font-size:13px;color:#667085}
.recent-list{display:grid;gap:8px}
.recent-item{background:#fff;border:1px solid #e5e9f0;border-radius:14px;padding:12px;display:flex;justify-content:space-between;gap:10px}
.guide{background:#eef4ff;border:1px solid #dbe7ff;border-radius:16px;padding:14px;margin:12px 0 18px}

.course-progress{background:#fff;border:1px solid #e3e9f2;border-radius:18px;padding:18px;margin:18px 0}
.course-progress .sec-title{display:flex;align-items:flex-start;gap:10px;margin-bottom:13px}
.course-progress .sec-icon{width:32px;height:32px;border-radius:10px;display:grid;place-items:center;background:#f1ecff;color:#8063cc;font-weight:900;flex:0 0 auto}
.course-progress .sec-kicker{color:#3976e8;font-size:11px;font-weight:950;letter-spacing:.09em;margin-bottom:3px}
.course-progress .sec-title h2{margin:0;font-size:17px}
.progress-layout{display:grid;grid-template-columns:220px 1fr;gap:16px;align-items:stretch}
.progress-side{border:1px solid #e3e9f2;border-radius:14px;padding:18px;background:#fff}
.progress-side .num{text-align:center;font-size:42px;font-weight:950;letter-spacing:-.06em;margin:8px 0 14px}
.track{height:10px;background:#e8edf5;border-radius:999px;overflow:hidden}
.fill{height:100%;background:linear-gradient(90deg,#3976e8,#6f9cf0)}
.legend{display:grid;gap:10px;margin-top:18px;font-size:12px;color:#56637a}
.legend span{display:flex;align-items:center;gap:8px}.legend i{width:14px;height:14px;border-radius:4px}
.course-current{margin-top:16px;padding:11px 12px;border-radius:12px;background:#edf3ff;color:#245ec9;font-size:13px;line-height:1.55}
.course-note{margin-top:8px;color:#667085;font-size:12px;line-height:1.55}

.gantt-frame{border:1px solid #e3e9f2;border-radius:14px;overflow:hidden;background:#fff}
.gantt-scroll{width:100%;overflow-x:auto;overflow-y:visible;-webkit-overflow-scrolling:touch;scrollbar-gutter:stable}
.gantt-scroll::-webkit-scrollbar{height:15px}
.gantt-scroll::-webkit-scrollbar-track{background:#edf1f6}
.gantt-scroll::-webkit-scrollbar-thumb{background:#9faabb;border-radius:999px;border:3px solid #edf1f6}
.gantt-board{min-width:1230px}
.gantt-header,.gantt-row{display:grid;grid-template-columns:300px 1fr}
.gantt-header{background:#f7f9fc;border-bottom:1px solid #e3e9f2}
.gantt-head-left{min-height:62px;display:flex;align-items:center;justify-content:center;border-right:1px solid #e3e9f2;font-size:12px;font-weight:900;color:#445168}
.timeline-header{display:grid}
.week{min-height:62px;display:flex;align-items:center;justify-content:center;border-right:1px solid #e3e9f2;font-size:12px;color:#46536a;font-weight:850;padding:0 5px;text-align:center}
.gantt-row{min-height:52px;border-bottom:1px solid #edf1f6}
.gantt-row.major .gantt-label{background:#f5f8ff;font-weight:900}
.gantt-row.middle .gantt-label{background:#fbfdfb;font-weight:850}
.gantt-label{display:flex;align-items:center;min-height:52px;border-right:1px solid #e3e9f2;padding:0 12px;font-size:12px;background:#fff}
.label-inner{display:flex;align-items:center;min-width:0}
.level-2{padding-left:22px}.level-3{padding-left:48px}
.tree-badge{width:21px;height:21px;border-radius:50%;display:grid;place-items:center;color:#fff;font-size:10px;font-weight:900;margin-right:8px;flex:0 0 auto}
.tree-badge.major{background:#3976e8}.tree-badge.middle{background:#66b37a}
.tree-num{width:31px;flex:0 0 auto;font-weight:900}
.tree-label{white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.timeline{position:relative;min-height:52px;display:grid;background:#fff}
.timeline::before{content:"";position:absolute;inset:0;background:repeating-linear-gradient(to right,transparent 0,transparent calc(var(--week-size,10%) - 1px),#e8edf4 calc(var(--week-size,10%) - 1px),#e8edf4 var(--week-size,10%));pointer-events:none}
.bar{position:relative;align-self:end;height:15px;border-radius:999px;margin:0 3px 8px;z-index:2;box-shadow:0 2px 6px rgba(30,48,80,.1);overflow:visible}
.bar[data-label]::after{content:attr(data-label);position:absolute;left:4px;bottom:19px;max-width:210px;padding:3px 7px;border-radius:7px;background:rgba(255,255,255,.96);border:1px solid rgba(210,219,232,.95);box-shadow:0 2px 7px rgba(30,48,80,.08);color:#3f4c63;font-size:10px;font-weight:850;line-height:1.2;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;pointer-events:none}
.bar.current[data-label]::after{color:#245ec9;border-color:#bad0fb;background:#f5f8ff}
.bar.done[data-label]::after{color:#2e8752;border-color:#c7e6d0;background:#f6fcf8}
.bar.plan[data-label]::after{color:#7458bd;border-color:#d8cdf4;background:#faf8ff}
.bar.group[data-label]::after{font-weight:900}
.bar.done{background:linear-gradient(90deg,#68b978,#83ca90)}
.bar.current{background:linear-gradient(90deg,#3976e8,#6899ef)}
.bar.plan{background:linear-gradient(90deg,#9c83df,#b79dec)}
.bar.group{height:7px;opacity:.5;box-shadow:none}
.today-line{position:absolute;top:0;bottom:0;width:2px;background:#ef5a63;z-index:3;pointer-events:none}
.today-label{position:absolute;top:-21px;transform:translateX(-50%);background:#ef5a63;color:#fff;border-radius:999px;padding:3px 7px;font-size:10px;font-weight:900;z-index:4}
.progress-empty{padding:16px;border:1px dashed #ccd3dd;border-radius:12px;color:#667085;margin-top:12px}
.gantt-dates{display:flex;justify-content:space-between;color:#6f7a8c;font-size:11px;padding:7px 2px 0}.gantt-dates b{color:#445168}
@media(max-width:760px){main{padding:16px 12px 48px}.dashboard,.todo-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.solution-split{grid-template-columns:1fr}.solution-problem-ref{position:static;max-height:none;overflow:visible}.problem{padding:14px}.progress-layout{grid-template-columns:1fr}.gantt-board{min-width:1100px}.gantt-header,.gantt-row{grid-template-columns:260px 1fr}.level-2{padding-left:14px}.level-3{padding-left:34px}}