:root{--blue:#367ea2;--ink:#244c60;--teal:#4e937d;--orange:#e6a553;--paper:#f2fbfc;--line:#c9e0e6;--violet:#7265a5}*{box-sizing:border-box}body{margin:0;color:var(--ink);background:#eaf6f7;font:16px/1.5 'Microsoft YaHei','PingFang SC',sans-serif}button,input,textarea,select{font:inherit}button{cursor:pointer;border:1px solid #bdd4dc;color:var(--ink);background:#f9ffff;border-radius:7px;padding:9px 17px;min-height:42px;font-weight:600;transition:background .15s}button:hover{background:#e1f0f5}button:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:3px solid #ffbf5e;outline-offset:3px}button:disabled{opacity:.4;cursor:default}input,textarea,select{background:#fff;border:1px solid #c9dade;border-radius:6px;padding:10px;color:var(--ink);min-width:0}label{display:flex;gap:9px;align-items:center}a{color:inherit}.lesson-header{display:flex;align-items:center;gap:12px;background:linear-gradient(105deg,#31628d,#559ebc);color:white;padding:12px 20px;box-shadow:0 3px 0 #c2e6ee;position:relative;z-index:3}.back{font-size:14px;text-decoration:none;white-space:nowrap}.brand{background:transparent;border:0;color:white;padding:0;white-space:nowrap;font-size:22px}.brand small{display:block;font-size:11px;font-weight:400;letter-spacing:2px;opacity:.8}.lesson-header nav{display:flex;gap:6px;flex:1;justify-content:center}.lesson-header nav button{border-radius:22px;background:#ffffff13;color:white;border-color:#ffffff40;padding:7px 12px;white-space:nowrap;font-size:14px}.lesson-header nav button.active{background:white;color:#377d9b;box-shadow:0 2px 6px #20435e33}.pager{display:flex;align-items:center;gap:4px;white-space:nowrap;font-size:13px}.pager button{color:white;background:#ffffff20;border:0;padding:6px 10px;min-height:34px}main{max-width:1600px;margin:0 auto;padding:24px 24px 16px;min-height:calc(100vh - 85px)}h1,h2,h3,p{margin:0}h2{font-size:21px}h3{font-size:18px}.heading{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px;gap:12px}.heading p{color:#648793;font-size:14px}.panel{background:#fff;border:1px solid #dce9ea;border-radius:9px;padding:16px;min-width:0;box-shadow:0 2px 8px #44768308}.stage{position:relative;min-width:0;overflow:hidden;border:2px solid #94b8c3;border-radius:7px;background:#f6fefe}.stage svg{display:block;width:100%;height:auto;max-height:calc(100vh - 235px);min-height:280px;touch-action:none;user-select:none}svg text{font-family:inherit;fill:var(--ink)}.actions{display:flex;gap:10px;align-items:center;justify-content:center;flex-wrap:wrap;margin-top:14px}.green{background:var(--teal);color:white;border-color:var(--teal)}.green:hover{background:#3c7f6b}.orange{background:var(--orange);color:#fff;border-color:var(--orange)}.orange:hover{background:#d8923d}.blue{background:var(--blue);color:white;border-color:var(--blue)}.blue:hover{background:#276e90}.purple{background:var(--violet);color:white;border-color:var(--violet)}.feedback{min-height:27px;color:#597783;font-size:14px;margin-top:12px;text-align:center}.two-columns{display:grid;grid-template-columns:minmax(0,1fr) 245px;gap:16px}.sidebar label{display:block;margin:18px 0 14px}.sidebar input{width:100%;margin-top:7px}.check-row{border-left:4px solid #d4e4e6;background:#f7fbfb;padding:14px 10px;margin:12px 0;color:#78939b}.check-row.done{border-color:var(--teal);color:#3b7667}.tip{padding:15px;background:#fff9e7;font-size:13px;color:#806b45;margin-top:20px}.muted{color:#78919a;font-size:13px}.welcome{min-height:calc(100vh - 146px);display:flex;flex-direction:column;align-items:center;justify-content:center;position:relative;overflow:hidden;background:linear-gradient(150deg,#f7ffff,#e7f4f5);border-radius:12px}.welcome:before,.welcome:after{content:'';position:absolute;pointer-events:none}.welcome:before{width:115px;height:115px;border:2px solid #cfe5e4;transform:rotate(27deg);top:15%;right:12%}.welcome:after{width:200px;height:200px;background:#d5eaf0;border-radius:50%;bottom:13%;right:10%;opacity:.55}.welcome h1{font-size:clamp(40px,5vw,74px);letter-spacing:5px;z-index:1}.welcome .eyebrow{color:#6d8b97;font-size:15px;margin-bottom:18px}.welcome p{color:#72929c;margin:18px 0 34px}.name-entry{background:#ffffffbf;border:1px solid #e1eded;padding:18px 22px;z-index:1;text-align:center}.name-entry label{margin:8px 0}.decor-lines{position:absolute;left:-50px;bottom:70px;width:340px;height:65px;border-top:4px solid #b8d8df;border-bottom:4px solid #b8d8df;transform:rotate(-15deg)}.global-tools{display:flex;justify-content:flex-end;gap:8px;margin-top:12px}.global-tools button{font-size:13px;padding:5px 12px;min-height:34px}.summary-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px}.discovery .stage svg{min-height:240px;max-height:calc(100vh - 300px)}.discovery h3{text-align:center;margin:8px 0}.discovery .panel{cursor:pointer}.sort-heading{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin-bottom:14px}.sort-heading h2{flex:1}.sort-heading button{font-size:13px;padding:7px 11px}.sort-board{position:relative;height:580px;min-height:420px;border:1px solid #d4e6e9;border-radius:9px;background:#f7fdfd;overflow:hidden;touch-action:none}.sort-zone{position:absolute;top:40px;bottom:15px;border:1px dashed #bdd9dd;border-radius:8px;pointer-events:none}.sort-zone span{position:absolute;top:-31px;left:0;right:0;text-align:center;font-size:15px;color:#688b95}.work-card{position:absolute;width:18%;min-width:125px;background:#fff;border:1px solid #c8dce3;padding:7px;border-radius:6px;box-shadow:0 4px 8px #2d67781a;cursor:grab;touch-action:none;user-select:none}.work-card:focus-visible{outline:3px solid var(--orange)}.work-card h3{font-size:12px;display:flex;gap:4px;justify-content:space-between;white-space:nowrap;overflow:hidden}.work-card svg{display:block;width:100%;height:90px;background:#effafa;margin-top:6px}.work-card.dragging{z-index:2;box-shadow:0 7px 15px #2d677830}.card-delete{border:0;padding:0 3px;min-height:20px;background:transparent;font-size:14px}.large-dialog{width:min(1100px,94vw);max-height:95vh;overflow:auto}dialog{border:1px solid #a5c5cb;border-radius:12px;color:var(--ink);padding:24px;max-width:min(600px,94vw);box-shadow:0 24px 70px #173c5c40}dialog::backdrop{background:#17354b9e}.dialog-head{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:16px}.dialog-head button{border:0;background:#eff7f8;font-size:23px;padding:0 9px;min-height:34px}.large-dialog{max-width:1100px}dialog label{display:flex;align-items:flex-start;flex-direction:column;margin:12px 0}dialog input,dialog textarea{width:100%}dialog p{margin:12px 0}#toast{position:fixed;top:90px;left:50%;transform:translateX(-50%);border-radius:7px;background:#25495e;color:#fff;padding:11px 22px;box-shadow:0 6px 20px #2d536533;z-index:20;max-width:90vw;display:none}.strip-layout{display:grid;grid-template-columns:minmax(0,1fr) 245px;gap:16px}.strip-info{padding:16px}.angle-big{font-size:36px;color:#366f8e;font-weight:700;margin:16px 0}.slider{width:min(460px,60vw);accent-color:var(--blue)}.task-page{max-width:950px;margin:30px auto}.task-page h1{font-size:36px;margin-bottom:25px}.task-page .task-body{white-space:pre-wrap;font-size:23px;line-height:2;min-height:300px}.outcome{display:grid;gap:18px;margin-top:25px}.outcome label{padding:18px;background:#f6fbfc;border-radius:8px}.outcome input{width:20px;height:20px}.line-handle{cursor:move}.lesson-line{cursor:move}.corner-note{text-align:center;font-size:13px;color:#728c94;margin:10px}#helpDialog p{line-height:1.9}.ruler-title{font-size:16px;font-weight:600}.ruler-description{border-top:1px solid #dce9ea;padding-top:10px}.badge{background:#edf8f2;color:#407b67;border-radius:4px;padding:5px 9px;font-size:13px}.degree-label{font-weight:bold}.local-note{color:#80989f;font-size:12px;text-align:center;margin:8px}
@media(min-width:1400px){.lesson-header nav button{padding:8px 17px}}@media(max-width:1150px){.lesson-header{flex-wrap:wrap;gap:8px}.lesson-header nav{order:3;width:100%;flex-basis:100%;justify-content:flex-start;overflow:auto}.pager{margin-left:auto}.brand{font-size:20px}main{padding:16px}.stage svg{max-height:none}.sort-board{height:540px}.two-columns,.strip-layout{grid-template-columns:minmax(0,1fr) 210px}.work-card svg{height:75px}}@media(max-width:720px){body{font-size:14px}.lesson-header{padding:10px}.brand{font-size:17px}.brand small{display:none}.back{font-size:12px}.lesson-header nav button{font-size:12px;padding:5px 9px;min-height:36px}.pager button{font-size:12px;padding:5px 7px}#fullscreen{display:none}main{padding:12px}.heading{display:block}.heading p{margin-top:5px}.two-columns,.strip-layout{grid-template-columns:1fr}.sidebar{display:grid;grid-template-columns:1fr 1fr;gap:6px 12px}.sidebar h3{grid-column:1/-1}.sidebar label{margin:5px 0}.sidebar .tip,.sidebar .muted{grid-column:1/-1;margin:0}.check-row{padding:10px 6px;margin:3px 0}.summary-grid{grid-template-columns:1fr}.stage svg{min-height:210px}.actions{gap:7px}.actions button{padding:8px 11px}.sort-board{height:720px}.work-card{width:28%;min-width:0}.work-card svg{height:75px}.work-card h3{font-size:10px}.sort-zone span{font-size:11px}.sort-heading h2{flex-basis:100%}.large-dialog{padding:12px}.strip-info{display:flex;gap:12px;align-items:center;flex-wrap:wrap}.strip-info p{flex-basis:100%}.strip-info .angle-big{font-size:28px;margin:0}.welcome p{text-align:center;padding:0 20px}.name-entry{padding:12px}.name-entry label{flex-direction:column}.welcome{min-height:70vh}.task-page .task-body{font-size:19px}.slider{width:70vw}}

.gallery-empty{position:absolute;inset:0;display:flex;flex-direction:column;justify-content:center;align-items:center;gap:18px;text-align:center;padding:20px;color:#648793}.gallery-empty button{pointer-events:auto}.work-card h3{padding-right:18px;min-height:20px}.card-delete{position:absolute;right:6px;top:5px}.ruler-tools{flex-basis:100%;display:flex;flex-wrap:wrap;gap:8px;align-items:center;justify-content:center;border-top:1px solid #dce9ea;padding-top:12px}.ruler-tools span{font-size:13px;color:#6c8590}.ruler-tools button{font-size:13px;padding:7px 12px}.rotating-line{cursor:grab}
@media(max-width:720px){.course21-ruler text[data-ruler-value]{font-size:28px}}
.purple:hover{background:#625491;color:white}
.strip-pivot-tools{display:flex;align-items:center;flex-wrap:wrap;gap:8px;margin-bottom:10px}.strip-pivot-tools strong{font-size:14px;margin-right:4px}.strip-pivot-tools button{font-size:14px;padding:7px 12px}.strip-pivot-tools button[aria-pressed="true"]{background:#fff2d8;border-color:#dba05b;color:#8c531f}.strip-pivot-tools p{flex-basis:100%;font-size:13px;color:#687f8a;min-height:20px}.strip-line-hit{cursor:grab}.strip-picking,.strip-picking .strip-line-hit{cursor:crosshair}#intersectionHint:empty{display:none}@media(max-width:720px){.strip-pivot-tools{gap:6px}.strip-pivot-tools strong{flex-basis:100%}.strip-pivot-tools button{font-size:13px}.strip-pivot-tools p{font-size:12px}}
.plane-tools{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin:8px 0 10px;padding:8px 10px;background:#f1f9fb;border:1px solid #c9e0e6;border-radius:7px}.plane-tools button{font-size:13px;padding:6px 10px;min-height:34px}.plane-mode,.plane-view{display:flex;gap:5px}.plane-view{margin-left:auto}.plane-tools button[aria-pressed="true"]{background:#367ea2;color:white;border-color:#367ea2}.plane-status{font-size:12px;color:#617f8d;flex-basis:100%}.plane-pan-mode{cursor:grab}.plane-grabbing{cursor:grabbing}.large-dialog{width:min(1320px,96vw);max-width:1320px}.discovery .plane-tools .plane-status{font-size:11px}.discovery .plane-tools button{font-size:12px;padding:5px 7px}@media(max-width:720px){.plane-tools{gap:6px;padding:7px}.plane-view{margin-left:0}.plane-tools button{font-size:12px;min-height:36px;padding:6px 8px}.large-dialog{width:94vw}.plane-status{font-size:11px}}
.large-dialog .dialog-head{position:sticky;top:-24px;z-index:4;background:white;padding:6px 0}.large-dialog #inspectStage .plane-tools{position:sticky;top:34px;z-index:3}@media(max-width:720px){.large-dialog .dialog-head{top:-12px}.large-dialog #inspectStage .plane-tools{top:40px}.intersection-marker text{font-size:36px;font-weight:600}.intersection-marker circle{r:8}}

/* Keep rotation controls beside the large plane for classroom operation. */
.strip-info{align-self:start}.strip-info>p{margin-top:12px}.strip-info .badge{display:inline-block;margin-top:8px}.strip-controls{border-top:1px solid var(--line);padding-top:16px;margin-top:20px}.strip-controls h3{font-size:16px}.strip-controls .actions{justify-content:flex-start;gap:8px}.strip-controls label{flex-wrap:wrap;width:100%;font-size:14px}.strip-controls .slider{width:100%;margin:0;min-height:34px;padding:0}.strip-controls button{font-size:14px;padding:9px 12px}.strip-controls #stripReset,.strip-controls #stripMark{width:100%}.strip-info #toggleAngle{width:100%}.sidebar>p.muted{margin-top:10px}.lesson-header nav{position:relative;scrollbar-width:thin}.strip-board-panel{padding-bottom:16px}
@media(min-width:721px){.large-dialog .stage svg{max-height:calc(95dvh - 380px);min-height:260px}}
@media(max-width:720px){.strip-controls{width:100%;margin-top:4px;padding-top:12px}.strip-controls .actions button{width:auto!important;flex:1 1 43%;min-height:44px}.strip-info>p{margin-top:0}.strip-info #toggleAngle{width:auto}.plane-tools button{min-height:44px}.plane-tools .plane-view{flex-wrap:wrap}.strip-pivot-tools button{min-height:44px}.strip-controls .slider{min-height:44px}}