:root{--paper:#f5f7fc;--white:#fff;--ink:#202e48;--muted:#7c879d;--line:#e5e9f2;--blue:#5365db;--blue-soft:#eef0fe;--mint:#248575;--mint-soft:#eaf5f0;--amber:#bc8030;--amber-soft:#fff5e5;--rose:#b94b63;--serif:Georgia,"Songti SC","STSong",serif;--sans:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif}
*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:14px/1.65 var(--sans)}button,input,a{-webkit-tap-highlight-color:transparent}button,a,input{font:inherit}button{cursor:pointer;border:0;background:transparent}button:disabled{cursor:default;opacity:.55}a{color:inherit;text-decoration:none}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid var(--blue);outline-offset:3px}
.sidebar nav{overflow:auto;min-height:0;flex:1}.sidebar{width:244px;position:fixed;inset:0 auto 0 0;background:#fff;border-right:1px solid var(--line);padding:32px 22px 18px;display:flex;flex-direction:column;z-index:5}
.brand{display:flex;align-items:center;gap:12px;margin:0 8px 36px;font-size:26px;font-weight:700;letter-spacing:2px}
.brand-symbol{font:30px var(--serif);color:#fff;background:var(--ink);width:45px;height:48px;display:grid;place-items:center;border-radius:13px;transform:rotate(-6deg)}
.brand-sub{display:block;font-size:10px;color:var(--muted);letter-spacing:1.4px;font-weight:400;margin-top:1px}
.catalog-label{font-size:10px;letter-spacing:1.5px;color:var(--muted);margin:0 12px 24px}
.course-label{display:flex;justify-content:space-between;font-size:12px;margin:0 12px 12px}
.course-label span{color:var(--muted)}
.course-button{display:flex;width:100%;gap:12px;text-align:left;padding:14px 12px;color:var(--muted);border-radius:12px;margin:4px 0;align-items:center}
.course-button.active{background:var(--blue-soft);color:var(--blue)}
.course-number{font:18px var(--serif);width:28px}
.course-button strong{display:block;font-size:13px;font-weight:650;color:inherit}
.course-button small{display:block;font-size:10px;margin-top:3px;opacity:.8}
.course-dot{margin-left:auto}
.sidebar-note{margin:28px 12px 12px;padding-top:22px;border-top:1px solid var(--line)}
.note-icon{display:block;font-size:28px;color:var(--blue);margin-bottom:6px}
.sidebar-note strong{font-size:13px;font-weight:600}
.sidebar-note p{font-size:12px;color:var(--muted);line-height:1.8;margin:6px 0 0}
.progress-card{margin-top:auto;padding:16px 12px 6px;font-size:12px}
.progress-card div{display:flex;justify-content:space-between}
.progress-card strong{color:var(--blue);font-weight:600}
.progress-card small{color:var(--muted);font-size:11px}
progress{width:100%;height:6px;border:0;margin:10px 0 6px;border-radius:99px;overflow:hidden;appearance:none;background:var(--line)}
progress::-webkit-progress-bar{background:var(--line)}
progress::-webkit-progress-value{background:var(--blue)}
.text-button{color:var(--muted);font-size:12px;text-align:left;padding:8px 12px}
.sidebar-footer{display:flex;justify-content:space-between;font-size:9px;letter-spacing:1px;color:var(--muted);margin:18px 12px 0}
main{margin-left:244px}
.topbar{height:74px;padding:0 42px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;background:#ffffffcc;position:sticky;top:0;z-index:4;backdrop-filter:blur(8px)}
.breadcrumb{font-size:12px;color:var(--muted)}
.breadcrumb span{margin:0 10px;color:#c0c7d4}
.breadcrumb strong{color:var(--ink);font-weight:600}
.toolbar{display:flex;align-items:center;gap:18px}
.offline{font-size:12px;color:var(--muted)}
.offline i{display:inline-block;width:7px;height:7px;border-radius:50%;background:var(--mint);margin-right:6px}
.icon-button{color:var(--ink);font-size:16px}
.icon-button span{font-size:12px;margin-left:4px}
.content{max-width:1180px;margin:0 auto;padding:34px 42px 28px}
.intro{display:flex;justify-content:space-between;gap:18px;align-items:flex-start}
.eyebrow{font-size:11px;letter-spacing:1.8px;color:var(--blue);font-weight:700}
h1{font-size:36px;line-height:1.25;font-weight:650;letter-spacing:.5px;margin:8px 0 10px}
.intro p{margin:0;color:var(--muted);max-width:680px}
.guide-button{border:1px solid var(--line);background:#fff;color:var(--muted);border-radius:999px;padding:8px 14px;white-space:nowrap}
.lesson-meta{display:flex;gap:8px;flex-wrap:wrap;margin:18px 0 22px}
.chip{font-size:12px;color:#68758e;background:#eef1f7;border:1px solid var(--line);border-radius:999px;padding:4px 10px}
.chip.level{color:var(--mint);background:var(--mint-soft);border-color:#d7ebe4}
.stage-bar{display:flex;justify-content:space-between;align-items:flex-end;border-bottom:1px solid #dfe4ef;margin-bottom:18px;gap:12px}
#stage-tabs{display:flex;gap:8px;flex-wrap:wrap}
.stage-tab{color:var(--muted);padding:8px 12px 12px;border-bottom:2px solid transparent;margin-bottom:-1px}
.stage-tab span{font:italic 14px var(--serif);margin-right:6px}
.stage-tab.active{color:var(--blue);border-color:var(--blue);font-weight:700}
.stage-hint{color:var(--muted);font-size:12px;padding-bottom:12px}
.experiment{display:grid;grid-template-columns:minmax(0,1fr) 300px;background:#fff;border:1px solid var(--line);border-radius:18px;min-height:430px;overflow:hidden}
.canvas-panel{padding:16px 16px 8px;display:flex;flex-direction:column;background:radial-gradient(#e6ebf5 1.1px,transparent 1.2px) 0 0/16px 16px,#fff}
.canvas-header{display:flex;justify-content:space-between;align-items:center;gap:8px}
.canvas-header strong{font-size:14px}
.live-badge{font-size:10px;letter-spacing:1px;color:var(--mint);border:1px solid #d7ebe4;background:var(--mint-soft);border-radius:999px;padding:3px 8px}
.canvas-panel svg{width:100%;height:276px;touch-action:none;user-select:none}
.canvas-caption{text-align:center;color:var(--muted);font-size:12px;padding:4px 8px 10px}
.controls{border-left:1px solid var(--line);padding:20px 18px}
.control-top{display:flex;justify-content:space-between;align-items:center}
.control-top h2{font-size:16px;margin:0}
.reset-exp{width:32px;height:32px;border-radius:50%;background:#f3f5fa;color:var(--muted)}
.control-description{color:var(--muted);font-size:12px;min-height:42px}
.slider-label{display:flex;justify-content:space-between;gap:8px;font-size:13px;margin-top:12px}
.slider-label output{color:var(--blue);font-weight:700}
input[type=range]{width:100%;accent-color:var(--blue);margin:6px 0}
.range-ends{display:flex;justify-content:space-between;color:var(--muted);font-size:11px}
.metric{margin-top:16px;padding-top:14px;border-top:1px solid var(--line)}
.metric-label{font-size:12px;color:var(--muted)}
.metric-number{font:40px/1 var(--sans);font-weight:650;letter-spacing:-.4px;margin:6px 0}
.metric-number small{font:14px var(--sans);color:var(--muted);margin-left:6px}
.meter{height:7px;background:#edf0f6;border-radius:99px;overflow:hidden}
.meter div{height:100%;background:linear-gradient(90deg,var(--blue),#7f8df0);width:0}
.metric-bottom{display:flex;justify-content:space-between;color:var(--muted);font-size:11px;margin-top:6px}
.status-pill{display:inline-flex;margin-top:10px;border-radius:999px;padding:4px 10px;font-size:12px;background:#f3f5fa;color:var(--muted)}
.status-pill.ok{background:var(--mint-soft);color:var(--mint)}
.status-pill.warn{background:var(--amber-soft);color:var(--amber)}
.secondary-button{width:100%;margin-top:14px;background:var(--blue-soft);color:var(--blue);border-radius:12px;padding:11px 12px;font-weight:650}
.observation{display:flex;gap:14px;align-items:center;margin-top:14px;background:var(--mint-soft);border-radius:16px;padding:16px 18px}
.observation-icon{width:36px;height:36px;display:grid;place-items:center;border-radius:12px;background:#fff;color:var(--mint);flex:none}
.observation p{margin:2px 0 0;color:#3d5c55;font-size:13px}
.formula{margin-left:auto;font:22px var(--serif);color:var(--mint);text-align:right;white-space:nowrap}
.lesson-footer{display:flex;justify-content:space-between;align-items:center;gap:16px;margin:22px 0 8px}
.lesson-footer span{color:var(--muted);font-size:13px}
.primary-button{background:var(--ink);color:#fff;border-radius:12px;padding:12px 16px;font-weight:650}
.bottom-note{display:flex;justify-content:space-between;gap:12px;border-top:1px solid var(--line);color:#a0a8b8;font-size:11px;padding:16px 0 8px}
.proof-layout{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:16px}
.proof-main,.proof-aside,.quiz-card{background:#fff;border:1px solid var(--line);border-radius:16px}
.proof-main{padding:24px 26px}
.proof-main h2,.quiz-header h2{margin:0 0 8px;font-size:22px}
.proof-intro,.quiz-header p{color:var(--muted);margin:0 0 8px}
.step{display:grid;grid-template-columns:42px 1fr;gap:8px;padding:14px 0;border-top:1px solid var(--line)}
.step b{font-size:12px;letter-spacing:1px;color:var(--blue)}
.step.locked{color:var(--muted)}
.step.locked p{margin:0}
.reveal-button{margin-top:8px}
.proof-aside{padding:18px}
.theorem{background:var(--blue-soft);border-radius:14px;padding:16px}
.theorem .math{font:26px/1.35 var(--serif)}
.theorem p,.callout p{margin:8px 0 0;font-size:13px}
.callout{margin-top:12px;border-radius:12px;padding:12px 14px;font-size:13px}
.callout.tip{background:var(--mint-soft)}
.callout.warn{background:var(--amber-soft)}
.quiz-header{margin-bottom:14px}
.questions{display:grid;grid-template-columns:1fr;gap:12px}
.quiz-card{padding:16px}
.quiz-card .tag{color:var(--blue);font-size:11px;letter-spacing:.4px}
.quiz-card h3{font-size:15px;line-height:1.55;min-height:0;margin:6px 0 10px}
.option{display:block;width:100%;text-align:left;background:#f6f8fc;border-radius:10px;padding:8px 10px;margin:6px 0;color:var(--ink)}
.option.selected{background:var(--blue-soft);box-shadow:inset 0 0 0 2px var(--blue)}
.option.correct{background:#e5f6ee;box-shadow:inset 0 0 0 2px var(--mint)}
.option.wrong{background:#fdecee;box-shadow:inset 0 0 0 2px var(--rose)}
.explain{font-size:12px;color:#526075;background:#f7f8fb;border-radius:10px;padding:8px 10px}
.explain.hidden{display:none}
.check-button{margin-top:8px}
dialog{width:min(620px,calc(100% - 28px));border:1px solid var(--line);border-radius:18px;padding:32px;color:var(--ink)}
dialog::backdrop{background:#19254166}
dialog h2{font-size:28px;line-height:1.35}
dialog li{margin:8px 0}
dialog .close-dialog.icon-button{position:absolute;right:16px;top:8px;font-size:26px}
.muted{color:var(--muted)}
#toast{position:fixed;left:50%;bottom:24px;transform:translate(-50%,12px);background:var(--ink);color:#fff;border-radius:999px;padding:10px 16px;opacity:0;pointer-events:none;transition:.2s;z-index:20}
#toast.visible{opacity:1;transform:translate(-50%,0)}
#print-handout{display:none}
.presenting .sidebar{display:none}
.presenting main{margin-left:0}
.presenting .content{max-width:1280px}
.presenting .canvas-panel svg{height:380px}
@media(max-width:1100px){.sidebar{width:210px}main{margin-left:210px}.content,.topbar{padding-left:22px;padding-right:22px}.experiment,.proof-layout{grid-template-columns:minmax(0,1fr) 250px}.questions{grid-template-columns:1fr}.stage-hint{display:none}}
@media(max-width:800px){.sidebar{position:static;width:auto;border-right:0;border-bottom:1px solid var(--line);padding:16px}.brand{margin-bottom:12px}.sidebar nav{display:flex;gap:6px;overflow:auto}.course-button{min-width:140px}.course-button small,.course-dot,.catalog-label,.sidebar-note,.progress-card,.text-button,.sidebar-footer,.course-label{display:none}main{margin-left:0}.topbar{height:auto;padding:12px 16px}.content{padding:20px 16px}.offline{display:none}h1{font-size:28px}.experiment,.proof-layout{grid-template-columns:1fr}.controls{border-left:0;border-top:1px solid var(--line)}.observation{align-items:flex-start;flex-wrap:wrap}.formula{margin-left:0}.lesson-footer{align-items:flex-start;flex-direction:column}}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}
@media print {
  body {
    background: #fff !important;
    color: #000 !important;
    font-size: 13px !important;
    line-height: 1.5 !important;
  }
  .sidebar, main, dialog, #toast, .toolbar, .timeline-bar {
    display: none !important;
  }
  #print-handout {
    display: block !important;
    padding: 0 !important;
  }
  #print-handout h1 {
    font-size: 22px !important;
    margin: 0 0 8px 0 !important;
    padding-bottom: 6px !important;
    border-bottom: 2px solid #000 !important;
  }
  #print-handout .meta-line, #print-handout p:first-of-type {
    margin: 4px 0 12px 0 !important;
    font-size: 12px !important;
  }
  
  /* CRUCIAL FIX: Avoid page break before the very first h2 / section */
  #print-handout h2 {
    font-size: 16px !important;
    margin: 14px 0 8px 0 !important;
    padding-top: 6px !important;
    break-before: auto !important;
    break-after: avoid !important;
  }
  #print-handout section {
    margin-bottom: 14px !important;
    break-inside: auto !important;
  }
  #print-handout section:first-of-type h2,
  #print-handout h2:first-of-type {
    break-before: avoid !important;
    margin-top: 6px !important;
  }
  
  /* Compact formula and callouts */
  .print-formula {
    font-size: 16px !important;
    background: #f8fafc !important;
    border: 1px solid #cbd5e1 !important;
    padding: 6px 10px !important;
    border-radius: 6px !important;
    margin: 6px 0 !important;
  }
  
  /* Keep each question compact and prevent splitting across pages */
  #print-handout ol, #print-handout ul {
    padding-left: 20px !important;
    margin: 6px 0 !important;
  }
  #print-handout li, #print-handout .question-item, .quiz-card {
    margin-bottom: 10px !important;
    break-inside: avoid !important;
    page-break-inside: avoid !important;
  }
  
  /* Answer key goes to final clean page if needed */
  .answer-key {
    break-before: page !important;
    margin-top: 0 !important;
    padding-top: 10px !important;
  }
  
  @page {
    size: A4 portrait;
    margin: 12mm 14mm 12mm 14mm;
  }
}
.quiz-toolbar{display:flex;justify-content:space-between;gap:16px;align-items:flex-end;margin-bottom:8px}
.quiz-toolbar .resample{width:auto;margin:0;white-space:nowrap}
.type-note{color:var(--muted);font-size:12px;margin:4px 0 0}
.answer-line{display:flex;gap:8px;align-items:center;margin:8px 0}
.answer-line input{flex:1;border:1px solid var(--line);border-radius:10px;padding:8px 10px;font:inherit;background:#f6f8fc}
.answer-line input.correct{box-shadow:inset 0 0 0 2px var(--mint)}
.answer-line input.wrong{box-shadow:inset 0 0 0 2px var(--rose)}
.explain{white-space:pre-wrap}

.memory-banner{margin:0 0 12px;padding:12px 14px;border-radius:14px;background:#eef0fe;color:#243056;font-weight:650}
.memory-banner[hidden]{display:none}
#memory-dialog{border:0;border-radius:18px;padding:22px;max-width:420px}
#memory-dialog h2{margin:8px 0 14px;font-size:22px}
.memory-options{display:grid;gap:8px}
#memory-feedback{min-height:1.4em;color:#526075}

.review-entry{display:flex;justify-content:space-between;align-items:center;width:100%;margin:0 0 14px;padding:12px 14px;border-radius:12px;background:#fff5e5;color:#8a5a16;text-align:left}
.review-entry strong{font-size:15px}
.review-entry small{font-size:11px}
.review-entry.active{outline:2px solid #bc8030}
.join-review{color:#5365db;font-weight:700;padding:0}
.review-card{background:#fff;border:1px solid #e5e9f2;border-radius:16px;padding:18px}
.review-list{margin:8px 0 16px;padding-left:18px;color:#526075}
.review-chains{display:flex;flex-direction:column;gap:8px}

.topbar{position:sticky}
.paper-panel{position:absolute;right:42px;top:68px;z-index:8;width:280px;background:#fff;border:1px solid var(--line);border-radius:16px;padding:16px 16px 8px;box-shadow:0 12px 40px #19254122}
.paper-panel[hidden]{display:none}
.paper-panel p{color:var(--muted);font-size:12px;margin:6px 0 10px}
.paper-panel label{display:flex;justify-content:space-between;align-items:center;gap:8px;margin:8px 0;font-size:13px}
.paper-panel select,.paper-panel input[type=number]{border:1px solid var(--line);border-radius:8px;padding:6px 8px;font:inherit;background:#fff}
.paper-check{justify-content:flex-start!important}
.paper-actions{display:flex;justify-content:space-between;align-items:center;margin-top:8px}
.paper-options p{margin:2px 0 2px 12px}
.paper-blank{margin:6px 0 14px;letter-spacing:.5px}
.paper-type{color:#5365db;font-size:12px}
.paper-cue{color:#526075}

/* paper-layout-fix */
.toolbar{flex-shrink:0}
.icon-button{white-space:nowrap;flex-shrink:0}
.paper-panel{position:fixed;top:78px;right:28px;z-index:30;width:300px;background:#fff;border:1px solid var(--line);border-radius:16px;padding:16px;box-shadow:0 16px 40px #19254133}
.paper-panel[hidden]{display:none!important}
.paper-panel strong{display:block;font-size:16px}
.paper-panel label{display:grid;grid-template-columns:72px 1fr;align-items:center;gap:8px;margin:10px 0;font-size:13px}
.paper-panel select,.paper-panel input[type=number]{width:100%;box-sizing:border-box}
.paper-check{grid-template-columns:16px 1fr!important}
@media print{.paper-panel{display:none!important}}


/* ================= Cognitive & Formula Upgrades ================= */
.katex-display {
  margin: 0.6em 0 !important;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 4px 0;
}
.katex {
  font-size: 1.08em;
  text-rendering: optimizeLegibility;
}
.memory-cue-box {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  background: rgba(32, 46, 72, 0.05);
  border-left: 4px solid #3b82f6;
  border-radius: 6px;
  padding: 10px 14px;
  margin: 10px 0;
  font-size: 14px;
  color: #1e293b;
  animation: fadeInCue 0.3s ease;
}
.memory-cue-box strong {
  color: #2563eb;
  white-space: nowrap;
}
.wrong-first-alert {
  background: #fef2f2;
  border-left-color: #ef4444;
  color: #991b1b;
}
@keyframes fadeInCue {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: translateY(0); }
}
.extreme-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin: 8px 0;
}
.extreme-btn {
  background: #f1f5f9;
  border: 1px solid #cbd5e1;
  border-radius: 4px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 600;
  color: #475569;
  cursor: pointer;
  transition: all 0.2s;
}
.extreme-btn:hover {
  background: #e2e8f0;
  color: #0f172a;
  border-color: #94a3b8;
}


/* Extreme Thinking Styles */
.extreme-box {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.08), rgba(245, 158, 11, 0.02));
  border: 1px dashed rgba(245, 158, 11, 0.5);
  border-radius: 8px;
  padding: 10px 12px;
  margin: 12px 0;
}
.extreme-title {
  font-size: 13px;
  font-weight: 700;
  color: #b45309;
  margin-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 4px;
}
.extreme-actions {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}
.extreme-btn {
  background: #ffffff;
  border: 1px solid #fcd34d;
  color: #92400e;
  border-radius: 4px;
  padding: 4px 8px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
}
.extreme-btn:hover {
  background: #fef3c7;
  border-color: #f59e0b;
  transform: translateY(-1px);
}


/* POE (Predict-Observe-Explain) Styles */
.poe-box {
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.08), rgba(99, 102, 241, 0.03));
  border: 1px solid rgba(59, 130, 246, 0.4);
  border-radius: 8px;
  padding: 12px;
  margin: 12px 0;
  animation: fadeInCue 0.3s ease;
}
.poe-title {
  font-size: 13px;
  font-weight: 700;
  color: #1d4ed8;
  display: flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 6px;
}
.poe-desc {
  font-size: 12px;
  color: #334155;
  margin-bottom: 8px;
  line-height: 1.4;
}
.poe-options {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.poe-btn {
  background: #ffffff;
  border: 1px solid #cbd5e1;
  border-radius: 6px;
  padding: 6px 10px;
  font-size: 12px;
  text-align: left;
  color: #1e293b;
  cursor: pointer;
  transition: all 0.15s ease;
}
.poe-btn:hover {
  border-color: #3b82f6;
  background: #eff6ff;
}
.poe-btn.poe-correct {
  background: #ecfdf5 !important;
  border-color: #10b981 !important;
  color: #065f46 !important;
  font-weight: 600;
}
.poe-btn.poe-wrong {
  background: #fef2f2 !important;
  border-color: #ef4444 !important;
  color: #991b1b !important;
}
.poe-feedback {
  margin-top: 8px;
  font-size: 12px;
  line-height: 1.4;
  padding: 8px;
  border-radius: 4px;
  background: #f8fafc;
}


/* ================= Domino Sorting Card Styles ================= */
.domino-container {
  margin: 14px 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.domino-card {
  display: flex;
  align-items: center;
  gap: 12px;
  background: #ffffff;
  border: 1.5px solid #cbd5e1;
  border-radius: 8px;
  padding: 10px 14px;
  cursor: grab;
  user-select: none;
  transition: all 0.2s ease;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}
.domino-card:hover {
  border-color: #3b82f6;
  background: #f8fafc;
}
.domino-card.dragging {
  opacity: 0.5;
  background: #eff6ff;
  border-color: #2563eb;
}
.domino-handle {
  color: #94a3b8;
  font-size: 16px;
  cursor: grab;
}
.domino-num {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: #e2e8f0;
  color: #475569;
  font-size: 12px;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.domino-text {
  font-size: 14px;
  color: #1e293b;
  font-weight: 500;
  flex: 1;
}
.domino-check-btn {
  margin-top: 10px;
}

/* ================= Universal Time Controller Styles ================= */
.timeline-bar {
  display: flex;
  align-items: center;
  gap: 10px;
  background: #f1f5f9;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  padding: 8px 14px;
  margin: 12px 0 6px 0;
}
.timeline-title {
  font-size: 12px;
  font-weight: 700;
  color: #475569;
  margin-right: 4px;
}
.time-ctrl-btn {
  background: #ffffff;
  border: 1px solid #cbd5e1;
  border-radius: 6px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 600;
  color: #334155;
  cursor: pointer;
  transition: all 0.15s ease;
  display: inline-flex;
  align-items: center;
  gap: 4px;
}
.time-ctrl-btn:hover {
  border-color: #3b82f6;
  color: #2563eb;
  background: #eff6ff;
}
.time-ctrl-btn.active {
  background: #2563eb;
  color: #ffffff;
  border-color: #2563eb;
}
.time-clock {
  font-family: monospace;
  font-size: 13px;
  font-weight: 700;
  color: #0f172a;
  background: #e2e8f0;
  padding: 2px 8px;
  border-radius: 4px;
  margin-left: auto;
}


/* ================= Final 3 Features: Invariance, Adversary, Review UI ================= */

/* 7. Invariance Detective Box */
.invariance-box {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.08), rgba(5, 150, 105, 0.02));
  border: 1.5px solid rgba(16, 185, 129, 0.4);
  border-radius: 8px;
  padding: 12px;
  margin: 12px 0;
  animation: fadeInCue 0.3s ease;
}
.invariance-title {
  font-size: 13px;
  font-weight: 700;
  color: #047857;
  display: flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 6px;
}
.invariance-desc {
  font-size: 12px;
  color: #334155;
  margin-bottom: 8px;
  line-height: 1.4;
}
.invariance-items {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}
.invariance-chip {
  background: #ffffff;
  border: 1px solid #cbd5e1;
  border-radius: 6px;
  padding: 8px 10px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 13px;
  color: #1e293b;
  transition: all 0.15s ease;
}
.invariance-chip:hover {
  border-color: #10b981;
  background: #f0fdf4;
}
.invariance-chip.state-same {
  background: #ecfdf5 !important;
  border-color: #10b981 !important;
  color: #065f46 !important;
  font-weight: 600;
}
.invariance-chip.state-changed {
  background: #fff1f2 !important;
  border-color: #f43f5e !important;
  color: #9f1239 !important;
  font-weight: 600;
}
.invariance-feedback {
  margin-top: 10px;
  font-size: 13px;
  padding: 8px 12px;
  border-radius: 6px;
  background: #ffffff;
  border: 1px solid #e2e8f0;
}

/* 8. Adversarial Debunk Box (常识小人打脸辩驳) */
.adversary-box {
  background: linear-gradient(135deg, rgba(239, 68, 68, 0.08), rgba(244, 63, 94, 0.02));
  border: 1.5px solid rgba(239, 68, 68, 0.4);
  border-radius: 8px;
  padding: 12px;
  margin: 12px 0;
  animation: fadeInCue 0.3s ease;
}
.adversary-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
}
.adversary-avatar {
  font-size: 22px;
  line-height: 1;
}
.adversary-name {
  font-size: 13px;
  font-weight: 700;
  color: #b91c1c;
}
.adversary-quote {
  background: #ffffff;
  border-left: 3px solid #ef4444;
  padding: 8px 12px;
  border-radius: 0 6px 6px 0;
  font-size: 13px;
  color: #475569;
  font-style: italic;
  margin-bottom: 8px;
}
.adversary-challenge {
  font-size: 12px;
  font-weight: 600;
  color: #1e293b;
  margin-bottom: 8px;
}
.adversary-actions {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.adversary-btn {
  background: #ffffff;
  border: 1px solid #f87171;
  color: #b91c1c;
  border-radius: 6px;
  padding: 6px 12px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
}
.adversary-btn:hover {
  background: #fef2f2;
  border-color: #ef4444;
  transform: translateY(-1px);
}
.adversary-verdict {
  margin-top: 10px;
  font-size: 13px;
  line-height: 1.4;
  padding: 8px 12px;
  border-radius: 6px;
  background: #ffffff;
  border: 1px solid #fee2e2;
  color: #991b1b;
}

/* 10. Review Drawer Polish */
.review-modal-enhanced {
  border-radius: 12px;
  padding: 24px;
  max-width: 640px;
  box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.2);
}
.review-stat-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin: 16px 0;
}
.review-stat-card {
  background: #f8fafc;
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  padding: 12px;
  text-align: center;
}
.review-stat-val {
  font-size: 20px;
  font-weight: 800;
  color: #2563eb;
}
.review-stat-lbl {
  font-size: 12px;
  color: #64748b;
  margin-top: 4px;
}


/* ================= Mobile & Touch Optimization (study.mipi.cc) ================= */
@media (max-width: 768px) {
  /* Prevent horizontal bouncing */
  html, body {
    overflow-x: hidden;
    -webkit-tap-highlight-color: transparent;
  }
  
  /* Layout: single column stacked */
  body {
    display: flex;
    flex-direction: column;
    padding-bottom: env(safe-area-inset-bottom, 20px);
  }
  
  /* Sidebar becomes a collapsible top header or clean vertical stack */
  .sidebar {
    width: 100% !important;
    min-width: 100% !important;
    border-right: none !important;
    border-bottom: 1px solid #e2e8f0;
    padding: 12px 16px !important;
    max-height: none !important;
    overflow-y: visible !important;
  }
  
  .brand {
    font-size: 18px !important;
    margin-bottom: 8px !important;
  }
  
  /* Horizontal scroll for course buttons on mobile for quick switching */
  #course-nav {
    display: flex !important;
    flex-wrap: nowrap !important;
    overflow-x: auto !important;
    -webkit-overflow-scrolling: touch;
    gap: 8px !important;
    padding: 6px 0 !important;
    scrollbar-width: none;
  }
  #course-nav::-webkit-scrollbar {
    display: none;
  }
  .course-button {
    flex: 0 0 auto !important;
    padding: 8px 12px !important;
    border-radius: 20px !important;
    white-space: nowrap !important;
    font-size: 13px !important;
  }
  
  /* Topbar and breadcrumbs */
  .topbar {
    padding: 10px 16px !important;
    flex-wrap: wrap !important;
    gap: 8px !important;
  }
  .toolbar {
    width: 100%;
    justify-content: flex-end;
    gap: 6px;
  }
  .toolbar button {
    padding: 6px 10px !important;
    font-size: 12px !important;
  }

  /* Main content container */
  main {
    padding: 12px 14px !important;
    width: 100% !important;
    max-width: 100vw !important;
  }
  
  /* Experiment area: full width canvas */
  .experiment {
    display: flex !important;
    flex-direction: column !important;
    gap: 14px !important;
  }
  .canvas-panel {
    width: 100% !important;
    border-radius: 10px !important;
    padding: 8px !important;
  }
  #experiment-svg {
    width: 100% !important;
    height: auto !important;
    min-height: 180px;
    touch-action: none; /* isolates canvas gesture */
  }
  
  /* Controls: comfortable touch target >= 44px */
  .controls {
    width: 100% !important;
    padding: 14px !important;
    border-radius: 10px !important;
  }
  
  /* Range Sliders: thicker track for thumb */
  input[type="range"] {
    height: 32px !important;
    cursor: pointer;
  }
  
  /* Buttons: larger tap areas */
  .time-ctrl-btn, .extreme-btn, .poe-btn, .secondary-button, .primary-button {
    min-height: 40px !important;
    display: inline-flex !important;
    align-items: center !important;
    justify-content: center !important;
    font-size: 13px !important;
    padding: 8px 14px !important;
  }
  
  .timeline-bar {
    flex-wrap: wrap !important;
    gap: 8px !important;
  }
  .time-clock {
    margin-left: 0 !important;
    width: 100%;
    text-align: center;
    padding: 4px !important;
  }
  
  .invariance-items {
    grid-template-columns: 1fr !important;
  }
  
  /* Math display horizontal scroll */
  .katex-display {
    max-width: 100vw;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    font-size: 0.95em;
  }
  
  /* Proof layout */
  .proof-layout {
    flex-direction: column !important;
  }
}


@media (max-width: 768px) {
  /* Compact sidebar header for mobile */
  .sidebar-note, .sidebar-footer {
    display: none !important;
  }
  .progress-card {
    padding: 8px 12px !important;
    margin: 8px 0 !important;
  }
  .review-entry {
    margin: 6px 0 !important;
    padding: 8px 12px !important;
  }
  
  /* Topbar breadcrumb compact */
  .breadcrumb {
    font-size: 14px !important;
  }
  
  /* Stage navigation bar */
  .stage-bar, nav.stages {
    display: flex !important;
    overflow-x: auto !important;
    gap: 6px !important;
    padding: 6px 0 !important;
    scrollbar-width: none;
  }
  .stage-bar button, nav.stages button {
    flex: 1 0 auto !important;
    min-height: 38px !important;
    padding: 6px 12px !important;
    font-size: 13px !important;
    white-space: nowrap !important;
  }
  
  /* SVG experiment canvas full bleed */
  .canvas-panel {
    margin: 0 !important;
    padding: 6px !important;
  }
  
  /* Domino sorting cards touch size */
  .domino-card {
    padding: 10px 10px !important;
    gap: 8px !important;
  }
  .domino-text {
    font-size: 13px !important;
  }
  .domino-up-btn, .domino-down-btn {
    min-width: 36px !important;
    min-height: 36px !important;
    padding: 4px !important;
  }
}


/* ================= Four Benchmark Styles ================= */
/* 1. PhET Dual Vectors */
.vector-tag {
  font-family: monospace;
  font-weight: 700;
  font-size: 11px;
}

/* 2. Desmos Tangent Triangle */
#tangent-probe-group {
  pointer-events: none;
  transition: opacity 0.15s ease;
}
.tangent-triangle {
  fill: rgba(245, 158, 11, 0.15);
  stroke: #f59e0b;
  stroke-width: 1.5;
  stroke-dasharray: 3,2;
}
.tangent-bubble {
  fill: #1e293b;
  rx: 4;
}
.tangent-bubble-text {
  fill: #ffffff;
  font-size: 11px;
  font-weight: bold;
}

/* 4. Explorable Tangle Text */
.tangle-num {
  color: #2563eb;
  border-bottom: 1.5px dashed #3b82f6;
  font-weight: 700;
  cursor: ew-resize;
  padding: 0 3px;
  border-radius: 2px;
  background: rgba(37, 99, 235, 0.05);
  transition: background 0.15s;
}
.tangle-num:hover {
  background: rgba(37, 99, 235, 0.15);
}