:root{
  --ink:#17305f;--muted:#71819c;--page:#edf7ff;--panel:#fff;--blue:#3d8df5;
  --blue-dark:#216ed6;--orange:#ff812e;--violet:#6654e8;--coral:#f36548;
  --yellow:#ffd443;--green:#39a674;--line:#dbe9f7;--soft:#f6faff;
  --shadow:0 14px 40px rgba(37,91,151,.11)
}
*{box-sizing:border-box}
html{background:var(--page);scroll-behavior:smooth}
body{margin:0;color:var(--ink);font-family:"PingFang SC","Microsoft YaHei",system-ui,sans-serif;background:linear-gradient(180deg,#dff1ff 0,#f7fbff 300px,#edf7ff 100%)}
button,input,select,textarea{font:inherit}
button{touch-action:manipulation}
main{width:min(1380px,calc(100% - 32px));margin:auto;padding:22px 0 max(56px,env(safe-area-inset-bottom))}

.site-header{min-height:126px;display:grid;grid-template-columns:auto minmax(0,1fr);align-items:center;gap:18px;padding:18px 28px;border-radius:28px 28px 12px 12px;background:var(--blue);color:#fff;box-shadow:var(--shadow);overflow:hidden}
.site-header small{display:block;margin-bottom:6px;color:#dcedff;font-size:12px;font-weight:800;letter-spacing:.08em}
.site-header h1{margin:0;font-size:clamp(28px,4vw,46px);line-height:1.15;letter-spacing:.02em}
.brand-mark{display:grid;place-items:center;width:58px;height:58px;border-radius:18px;background:#fff;color:var(--blue);font-size:18px;font-weight:1000;transform:rotate(-5deg)}

.layout{display:grid;grid-template-columns:minmax(330px,400px) minmax(0,1fr);align-items:start;gap:18px;margin-top:18px}
.question-card,.answer-card,.book-bank{background:rgba(255,255,255,.96);border:1px solid var(--line);border-radius:24px;box-shadow:var(--shadow)}
.question-card{position:sticky;top:14px;min-width:0;padding:24px}
.answer-card{min-width:0;padding:28px}
.section-title{display:flex;align-items:center;gap:10px;margin-bottom:14px}
.section-title span{display:grid;place-items:center;width:32px;height:32px;border-radius:11px;background:var(--yellow);font-weight:1000}
.section-title h2{margin:0;font-size:19px}

aside textarea{width:100%;min-height:188px;resize:vertical;border:2px solid var(--line);border-radius:18px;padding:16px;color:var(--ink);background:#fbfdff;line-height:1.7;outline:none;font-size:15px}
aside textarea::placeholder{color:#9aabc1}
aside textarea:focus{border-color:var(--blue);box-shadow:0 0 0 4px rgba(61,141,245,.12)}
.parse,#solve{width:100%;min-height:52px;border:0;border-radius:15px;color:#fff;font-weight:1000;cursor:pointer;transition:transform .18s,box-shadow .18s}
.parse{margin-top:12px;background:var(--orange);box-shadow:0 7px 0 #dc5d13;font-size:18px}
.parse:hover,#solve:hover{transform:translateY(-1px)}
.parse:active,#solve:active{transform:translateY(3px);box-shadow:none}
.parse-result{margin:15px 2px;color:var(--muted);font-size:12px;line-height:1.55}
.parse-result.ok{color:var(--green);font-weight:800}.parse-result.bad{color:#c34232}

details{min-width:0;border-top:1px solid var(--line);padding-top:14px}
details summary{cursor:pointer;color:var(--ink);font-size:14px;font-weight:1000;list-style:none}
details summary::-webkit-details-marker{display:none}
details summary::after{content:"＋";float:right;color:var(--blue);font-size:20px;line-height:1}
details[open] summary::after{content:"−"}
details summary span{display:block;margin-top:3px;color:var(--muted);font-size:10px;font-weight:600}
.types{display:flex;width:100%;max-width:100%;gap:8px;margin:16px 0 20px;padding-bottom:5px;overflow-x:auto;overscroll-behavior-inline:contain;scrollbar-width:thin}
.types button{flex:0 0 auto;min-height:42px;border:1px solid var(--line);border-radius:13px;background:#f7fbff;padding:9px 12px;color:var(--muted);font-size:12px;font-weight:800;cursor:pointer}
.types button.active{border-color:var(--blue);background:var(--blue);color:#fff;box-shadow:0 5px 14px rgba(61,141,245,.22)}
.field-title{margin-bottom:10px;font-size:13px;font-weight:1000}
.fields{display:grid;grid-template-columns:1fr 1fr;gap:10px}
.fields label{color:var(--muted);font-size:11px;font-weight:700}.fields label.wide{grid-column:1/-1}
.fields input,.fields select{display:block;width:100%;min-height:42px;margin-top:5px;border:1px solid var(--line);border-radius:12px;padding:9px 10px;color:var(--ink);background:#fff;outline:none}
.fields input:focus,.fields select:focus{border-color:var(--blue)}
#solve{margin-top:14px;background:var(--blue);box-shadow:0 6px 0 var(--blue-dark);font-size:14px}
#error{min-height:18px;margin:11px 0 0;color:#c34232;font-size:12px}

.top{display:flex;justify-content:space-between;align-items:flex-start;gap:20px;padding-bottom:18px;border-bottom:1px solid var(--line)}
.top small{color:var(--blue);font-size:11px;font-weight:1000;letter-spacing:.08em}.top h2{margin:4px 0 0;font-size:25px}
.top strong{max-width:52%;text-align:right;color:var(--green);font-size:clamp(20px,2.4vw,30px);line-height:1.25}
.steps{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin:18px 0}
.step{display:grid;grid-template-columns:36px 1fr;align-items:start;gap:10px;padding:15px;border:1px solid var(--line);background:var(--soft);border-radius:16px}
.step i{display:grid;place-items:center;width:32px;height:32px;border-radius:11px;background:var(--violet);color:#fff;font-style:normal;font-weight:1000}
.step:nth-child(3n+2) i{background:var(--coral)}.step:nth-child(3n) i{background:var(--green)}
.step small{color:var(--muted);font-size:11px}.step b{display:block;margin-top:5px;font-size:14px;line-height:1.5;overflow-wrap:anywhere}
.empty{grid-column:1/-1;margin:0;padding:28px;text-align:center;color:var(--muted);background:var(--soft);border-radius:16px}
.diagram{margin-top:18px;padding:18px;border:1px solid var(--line);border-radius:20px;background:#fff}
.diagram-head{display:flex;justify-content:space-between;align-items:center;gap:16px}.diagram-head h3{margin:0;font-size:18px}.diagram-head span{font-size:11px;color:var(--muted);text-align:right}
svg{width:100%;height:auto;margin-top:5px}.events{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px}.event{padding:8px 11px;border-radius:10px;background:#edf6ff;color:var(--ink);font-size:11px;font-weight:700}

.book-bank{margin-top:18px;padding:20px 24px}.book-bank>summary{display:flex;justify-content:space-between;align-items:center}.book-bank>summary span{font-size:17px}.book-bank>summary small{margin-right:30px;color:var(--muted);font-size:11px}.book-bank #bookCases{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin-top:18px}
.case{border:1px solid var(--line);border-radius:14px;background:#fff;padding:14px;text-align:left;color:var(--ink);cursor:pointer}.case:hover{border-color:var(--blue);background:#f7fbff}.case b,.case span{display:block}.case span{margin-top:6px;color:var(--muted);font-size:10px;line-height:1.5}
.solver-internals[hidden]{display:none!important}

@media(max-width:1100px){.layout{grid-template-columns:340px minmax(0,1fr)}.steps{grid-template-columns:1fr}.book-bank #bookCases{grid-template-columns:repeat(3,1fr)}}
@media(max-width:820px){
  body{background:linear-gradient(180deg,#dff1ff 0,#f7fbff 220px,#edf7ff 100%)}
  main{width:min(100% - 20px,680px);padding-top:max(10px,env(safe-area-inset-top))}
  .site-header{min-height:98px;grid-template-columns:auto minmax(0,1fr);padding:14px 18px;border-radius:22px 22px 10px 10px;gap:12px}.site-header>div:nth-child(2){min-width:0}.site-header small{font-size:10px}.site-header h1{font-size:clamp(22px,6vw,30px);overflow-wrap:anywhere}.brand-mark{width:44px;height:44px;border-radius:13px;font-size:14px}
  .layout{grid-template-columns:minmax(0,1fr);gap:12px;margin-top:12px}.layout>*{min-width:0}.question-card{position:static;width:100%;padding:18px}.answer-card{width:100%;padding:18px}.question-card,.answer-card,.book-bank{border-radius:20px}
  aside textarea{min-height:138px}.parse{min-height:54px}
  .top{display:block}.top strong{display:block;max-width:none;margin-top:10px;text-align:left}.steps{grid-template-columns:1fr}
  .diagram{padding:14px}.diagram-head{align-items:flex-start}.diagram-head span{max-width:150px}
  .book-bank{padding:18px}.book-bank #bookCases{grid-template-columns:1fr 1fr}
}
@media(max-width:480px){
  main{width:calc(100% - 14px)}.site-header h1{font-size:20px;line-height:1.25}
  .section-title h2{font-size:17px}.fields{grid-template-columns:1fr 1fr}.book-bank #bookCases{grid-template-columns:1fr}
  .top h2{font-size:22px}.diagram-head{display:block}.diagram-head span{display:block;margin-top:4px;text-align:left}
}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}.parse,#solve{transition:none}}

/* 方案 1：让孩子依次“看过程—找关系—列算式”，而不是同时阅读所有信息。 */
:root{--page:#f5f8fc;--panel:#fff;--line:#dfe7f1;--soft:#f8faff;--shadow:0 10px 28px rgba(30,61,105,.08)}
body{background:linear-gradient(180deg,#eaf2ff 0,#f8fbff 260px,#f5f8fc 100%)}
main{width:min(1180px,calc(100% - 32px));padding-top:18px}
.site-header{min-height:88px;padding:14px 22px;border:1px solid var(--line);border-radius:22px;background:rgba(255,255,255,.94);color:var(--ink);box-shadow:none}
.site-header small{color:var(--muted);letter-spacing:.04em}.site-header h1{font-size:clamp(25px,3vw,36px);letter-spacing:0}.brand-mark{width:48px;height:48px;border-radius:15px;background:var(--violet);color:#fff;font-size:16px}
.layout{display:block;margin-top:14px}
.question-card,.answer-card{border-radius:22px;box-shadow:var(--shadow)}
.question-card{position:static;display:grid;grid-template-columns:220px minmax(0,1fr);gap:18px;align-items:start;padding:18px 20px}
.question-copy{padding:5px 3px}.question-copy p{margin:0;color:var(--muted);font-size:13px;line-height:1.6}.section-title{margin-bottom:7px}.section-title span{width:28px;height:28px;border-radius:9px;background:#d9f36a}.section-title h2{font-size:18px}
.question-entry{display:grid;grid-template-columns:minmax(0,1fr) 142px;gap:12px;align-items:stretch}.question-card textarea{min-height:104px;height:104px;padding:13px 15px;border-radius:14px;font-size:14px;line-height:1.55}.question-actions{display:flex;flex-direction:column;justify-content:center}.parse{min-height:48px;margin:0;border-radius:13px;box-shadow:0 5px 0 #dc5d13;font-size:16px}.parse-result{margin:12px 2px 0;font-size:11px;text-align:center}.question-card #error{grid-column:2;margin:0}
.answer-card{margin-top:14px;padding:24px;background:rgba(255,255,255,.98)}
.answer-card.is-empty .learning-journey{display:none}.answer-card.is-empty .top{padding-bottom:0;border-bottom:0}
.top{padding:0 2px 18px}.top small{color:var(--violet);font-size:11px}.top h2{font-size:26px}.top strong{display:inline-flex;align-items:center;max-width:54%;padding:9px 14px;border-radius:13px;background:#edf8ef;color:var(--green);font-size:clamp(17px,2vw,24px);text-align:left}
.learning-journey{display:grid;gap:14px}.journey-guide{display:flex;align-items:center;gap:16px;padding:12px 14px;border-bottom:1px solid var(--line);color:var(--muted)}.journey-guide>span{color:var(--ink);font-size:13px;font-weight:1000}.journey-guide ol{display:flex;flex:1;gap:0;justify-content:flex-start;margin:0;padding:0;list-style:none;counter-reset:journey}.journey-guide li{position:relative;display:flex;align-items:center;gap:7px;min-width:148px;color:var(--muted);font-size:12px;font-weight:800}.journey-guide li::before{display:grid;place-items:center;width:22px;height:22px;border-radius:50%;background:#eef1f7;color:var(--violet);content:counter(journey);counter-increment:journey;font-size:11px;font-weight:1000}.journey-guide li:not(:last-child)::after{width:40px;height:2px;margin-left:5px;background:#dce3ed;content:""}.journey-guide li:first-child::before{background:var(--violet);color:#fff}
.learning-stage{padding:18px;border:1px solid var(--line);border-radius:18px;background:#fff}.observe-stage{background:linear-gradient(135deg,#fff 0,#f8f7ff 100%)}.relationship-stage{background:linear-gradient(135deg,#fff 0,#f7fbf8 100%)}.calculate-stage{background:linear-gradient(135deg,#fff 0,#fffaf5 100%)}
.stage-head{display:flex;align-items:flex-start;gap:10px}.stage-number{display:grid;place-items:center;flex:0 0 auto;width:30px;height:30px;border-radius:10px;background:var(--violet);color:#fff;font-size:14px;font-weight:1000}.relationship-stage .stage-number{background:var(--green)}.calculate-stage .stage-number{background:var(--orange)}.stage-head h3{margin:1px 0 2px;color:var(--ink);font-size:17px;line-height:1.25}.stage-head p{margin:0;color:var(--muted);font-size:11px;line-height:1.5}
.diagram{margin:0;padding:0;border:0;background:transparent}.diagram-head{display:none}
.animation-controls{grid-template-columns:auto auto minmax(130px,1fr) minmax(180px,auto);gap:8px;margin:14px 0 0;padding:8px 10px;background:rgba(255,255,255,.72);border:1px solid #e6e3ff;border-radius:13px}.animation-controls label{display:none}.animation-controls input{grid-column:auto}.animation-controls output{font-size:11px;white-space:nowrap}.animation-controls button{min-height:36px;border-radius:10px;padding:6px 10px;font-size:12px}
.motion-panel{margin-top:10px;padding:10px 14px 8px;border-color:#e5e1ff;border-radius:14px;background:#fff}.motion-heading strong{font-size:13px}.motion-heading span{font-size:10px}.motion-equation{min-height:1.4em;margin:0;padding:6px 8px;border-radius:9px;background:#f7f5ff;color:#4d3ac0;font-size:11px;line-height:1.45}
.relationship-stage #svg{display:block;margin:9px auto 0;max-height:340px}.events{display:none}
.steps{grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:10px;margin:14px 0 0}.step{grid-template-columns:30px 1fr;gap:9px;padding:13px;border-radius:13px;background:rgba(255,255,255,.84)}.step i{width:28px;height:28px;border-radius:9px;font-size:11px}.step small{font-size:10px}.step b{margin-top:4px;font-size:13px;line-height:1.48}
.final-equation{margin-top:12px;padding:14px 16px;border-color:#ffe0c5;border-radius:14px;background:#fff7ef}.final-equation small{color:#c45f1d}.final-equation>strong{margin-top:5px;color:var(--ink);font-size:15px;line-height:1.5}.equation-details{margin-top:10px;padding-top:10px;border-top:1px solid #f6dfcb}.equation-details summary{color:#b85b20;font-size:12px;font-weight:900}.equation-details summary::after{color:#b85b20;font-size:16px}.final-equation ol{grid-template-columns:repeat(auto-fit,minmax(210px,1fr));margin-top:10px}.final-equation li{padding:8px;font-size:10px}.final-equation li i{width:21px;height:21px;border-radius:7px;font-size:9px}
@media(max-width:820px){main{width:min(100% - 20px,680px);padding-top:max(10px,env(safe-area-inset-top))}.site-header{min-height:72px;padding:11px 14px;border-radius:18px}.site-header small{font-size:9px}.site-header h1{font-size:22px}.brand-mark{width:38px;height:38px;border-radius:12px;font-size:12px}.question-card{grid-template-columns:1fr;padding:16px;gap:10px}.question-copy{padding:0}.question-entry{grid-template-columns:1fr}.question-card textarea{min-height:120px;height:120px}.question-actions{display:grid;grid-template-columns:132px 1fr;gap:12px;align-items:center}.parse-result{margin:0;text-align:left}.question-card #error{grid-column:auto}.answer-card{margin-top:12px;padding:16px}.top{padding-bottom:14px}.top h2{font-size:23px}.top strong{max-width:none;margin-top:9px;font-size:17px}.journey-guide{gap:10px;padding:10px 2px}.journey-guide>span{font-size:12px}.journey-guide li{min-width:0;flex:1;gap:5px;font-size:11px}.journey-guide li:not(:last-child)::after{width:16px;margin-left:3px}.learning-stage{padding:14px;border-radius:16px}.stage-head h3{font-size:16px}.animation-controls{grid-template-columns:auto auto 1fr;margin-top:12px}.animation-controls input{grid-column:1/-1}.animation-controls output{grid-column:1/-1;text-align:left}.motion-panel{padding:9px 10px}.relationship-stage #svg{max-height:none}.steps{grid-template-columns:1fr}.final-equation ol{grid-template-columns:1fr}}
@media(max-width:420px){main{width:calc(100% - 14px)}.site-header h1{font-size:20px}.question-actions{grid-template-columns:1fr}.parse-result{text-align:center}.journey-guide>span{display:none}.journey-guide li{font-size:10px}.journey-guide li:not(:last-child)::after{width:8px}.learning-stage{padding:12px}.stage-number{width:28px;height:28px}.top h2{font-size:21px}}

/* 样板落地：左侧说明、右侧学习画布。 */
:root{--ink:#16315f;--muted:#78889e;--page:#fbfcff;--line:#e3e8f1;--violet:#7055e9;--orange:#ff7047;--green:#579373;--soft:#f7f9fd;--shadow:0 8px 24px rgba(35,57,93,.07)}
html,body{background:#fbfcff}body{background:linear-gradient(180deg,#fff 0,#f8faff 100%)}
main{width:min(1500px,calc(100% - 40px));padding:18px 0 54px}
.site-header{display:flex;justify-content:center;min-height:104px;padding:16px 24px;border:1px solid #dbe4f1;border-radius:20px;background:#fff;color:var(--ink);text-align:center;box-shadow:0 6px 20px rgba(35,57,93,.035)}
.site-header .brand-mark{display:none}.site-header h1{font-size:clamp(30px,3.1vw,46px);line-height:1.1;letter-spacing:.01em}.site-header small{margin:9px 0 0;color:#73839a;font-size:15px;font-weight:700;letter-spacing:0}
.layout{margin-top:16px}.question-card{grid-template-columns:205px minmax(0,1fr);gap:22px;padding:20px 26px;border-radius:18px;box-shadow:0 5px 18px rgba(35,57,93,.04)}
.question-copy{border-right:1px solid #edf0f5}.question-copy p{max-width:170px;font-size:13px}.section-title span{width:34px;height:34px;border-radius:50%;background:var(--violet);color:#fff}.section-title h2{font-size:21px}.question-entry{grid-template-columns:minmax(0,1fr) 166px;gap:14px}.question-card textarea{height:98px;min-height:98px;border-color:#dce4ee;border-radius:14px;background:#fcfdff;font-size:15px}.parse{min-height:48px;background:var(--violet);box-shadow:0 5px 0 #503aca}.parse-result{font-size:11px}
.answer-card{margin-top:16px;padding:18px;border-radius:20px;box-shadow:0 8px 24px rgba(35,57,93,.055)}.top{align-items:center;padding:5px 6px 16px}.top small{color:var(--violet)}.top h2{font-size:26px}.top strong{padding:10px 14px;border-radius:12px;background:#eff9f3;color:#4a8a68}
.journey-guide{display:none}.learning-journey{gap:14px}.learning-stage{display:grid;grid-template-columns:180px minmax(0,1fr);gap:18px;align-items:stretch;padding:20px 18px;border-radius:18px;background:#fff;box-shadow:0 4px 14px rgba(37,59,92,.045)}.observe-stage{background:linear-gradient(100deg,#fff 0,#fbfaff 100%)}.relationship-stage{background:linear-gradient(100deg,#fff 0,#fbfefd 100%)}.calculate-stage{background:linear-gradient(100deg,#fff 0,#fffcf8 100%)}
.stage-head{flex-direction:column;justify-content:center;align-self:stretch;gap:9px;padding:8px 10px 8px 14px;border-right:1px solid #edf0f5}.stage-number{width:44px;height:44px;border-radius:50%;font-size:17px;box-shadow:0 4px 10px rgba(112,85,233,.18)}.stage-head h3{font-size:25px;line-height:1.15}.stage-head p{max-width:138px;font-size:13px;line-height:1.55}.stage-content{min-width:0;display:flex;flex-direction:column;justify-content:center}
.animation-controls{grid-template-columns:auto auto minmax(120px,1fr) minmax(170px,auto);margin:0 0 10px;padding:8px 10px;border:1px solid #e6e4fb;border-radius:12px;background:#faf9ff}.animation-controls button{min-height:38px;border-radius:10px;font-size:12px}.animation-controls button:first-child{background:var(--violet);border-color:var(--violet)}
.motion-panel{margin:0;padding:12px;border-color:#dfe7f1;border-radius:14px;background:#fff}.motion-panel.train-lesson{border-color:#dfe6fa;background:#fff}.motion-panel.train-lesson #motionSvg{border-radius:10px;background:#e9f8ff}.motion-panel.train-lesson .motion-heading{position:relative;z-index:1}.motion-panel.train-lesson .motion-equation{background:rgba(247,245,255,.94)}.motion-heading strong{font-size:14px}.motion-heading span{font-size:11px}.motion-equation{margin-top:4px;padding:8px 10px;text-align:left;font-size:12px}
.relationship-stage #svg{margin:0;max-height:285px}.steps{grid-template-columns:repeat(auto-fit,minmax(205px,1fr));gap:10px;margin:0}.step{min-height:92px;padding:15px;border-color:#e6eaf1;background:#fbfcff}.step i{width:31px;height:31px;border-radius:50%}.step small{font-size:11px}.step b{font-size:14px}.final-equation{margin-top:12px;border-color:#ffe6d5;background:#fff9f4}.final-equation>strong{font-size:17px}.equation-details{display:none}
@media(max-width:820px){main{width:min(100% - 20px,680px)}.site-header{min-height:86px;padding:14px;border-radius:16px}.site-header h1{font-size:28px}.site-header small{margin-top:5px;font-size:12px}.question-card{grid-template-columns:1fr;padding:16px}.question-copy{border:0}.question-copy p{max-width:none}.question-entry{grid-template-columns:1fr}.question-card textarea{height:118px}.question-actions{grid-template-columns:150px 1fr}.answer-card{padding:12px;border-radius:16px}.learning-stage{grid-template-columns:1fr;gap:12px;padding:15px}.stage-head{flex-direction:row;align-items:center;gap:10px;padding:0 0 10px;border-right:0;border-bottom:1px solid #edf0f5}.stage-number{width:34px;height:34px;font-size:14px}.stage-head h3{font-size:19px}.stage-head p{max-width:none;font-size:11px}.animation-controls{grid-template-columns:auto auto 1fr}.animation-controls input{grid-column:1/-1}.animation-controls output{grid-column:1/-1}.motion-panel{padding:10px}.relationship-stage #svg{max-height:none}.steps{grid-template-columns:1fr}.step{min-height:0}}

/* 第一版模板：暖白纸张 + 三块并列学习卡。保留解题逻辑，只重置视觉层。 */
:root{
  --ink:#233b72;
  --muted:#71809a;
  --page:#fffdf8;
  --line:#d9e2f0;
  --violet:#6d57eb;
  --orange:#ff8051;
  --yellow:#ffd45f;
  --green:#5b9c78;
  --sky:#e7f6ff;
  --shadow:0 10px 24px rgba(67,75,142,.10);
}
html,body{background:var(--page)}
body{background:linear-gradient(180deg,#fffdf8 0,#f8fbff 74%,#fffdf8 100%)}
main{width:min(1440px,calc(100% - 32px));padding:16px 0 42px}
.site-header{
  position:relative;display:block;min-height:119px;padding:14px 236px 14px 30px;
  overflow:visible;border:0;border-radius:0;background:transparent;color:var(--ink);box-shadow:none;text-align:left;
}
.site-header .brand-mark{display:none}
.brand-copy{position:relative;z-index:1}
.brand-kicker{margin:0 0 5px;color:#ef8b49;font-size:12px;font-weight:900;letter-spacing:.1em}
.site-header h1{margin:0;font-size:clamp(31px,3.2vw,45px);font-weight:1000;line-height:1.04;letter-spacing:.02em;white-space:nowrap}
.site-header h1 span{color:var(--violet)}
.site-header h1 em{margin-left:.16em;color:var(--orange);font-style:normal}
.site-header small{margin:8px 0 0;color:#74829a;font-size:15px;font-weight:800;letter-spacing:.02em}
.mascot-corner{position:absolute;right:18px;bottom:-6px;z-index:2;display:flex;align-items:flex-end;gap:8px}
.mascot-corner img{display:block;width:128px;height:112px;border-radius:16px;object-fit:contain;object-position:center;filter:drop-shadow(0 6px 6px rgba(61,75,126,.14))}
.mascot-bubble{max-width:132px;margin-bottom:35px;padding:10px 12px;border:2px solid #d9ccff;border-radius:16px 16px 4px 16px;background:#fff;color:#624ec8;font-size:12px;font-weight:1000;line-height:1.35;box-shadow:0 5px 12px rgba(87,66,180,.09)}

.layout{margin-top:0}
.question-card{
  position:relative;display:grid;grid-template-columns:278px minmax(0,1fr);gap:22px;align-items:center;
  padding:19px 24px;border:1px solid #e2e5f0;border-radius:24px;background:#fff;box-shadow:var(--shadow);
}
.question-copy{padding:5px 18px 5px 3px;border-right:1px solid #ebe9f3}
.question-copy p{max-width:175px;margin:7px 0 0;color:var(--muted);font-size:13px;font-weight:700;line-height:1.55}
.section-title{flex-wrap:nowrap;gap:10px;margin:0}.section-title span{display:grid;place-items:center;width:42px;height:42px;border-radius:14px;background:#f2efff}.section-title span img{width:34px;height:34px;object-fit:contain}.section-title h2{margin:0;color:var(--ink);font-size:22px;font-weight:1000;white-space:nowrap}
.practice-toggle{display:inline-flex;min-height:32px;flex:none;align-items:center;justify-content:center;margin-left:auto;padding:6px 10px;border:1px solid #ffc27c;border-radius:11px;background:linear-gradient(180deg,#ffb75c,#f4843d);box-shadow:0 2px 0 #d96728;color:#fff;font-size:13px;font-weight:1000;line-height:1;letter-spacing:0;white-space:nowrap;cursor:pointer}.practice-toggle:hover,.practice-toggle[aria-expanded="true"]{border-color:#ed9445;background:linear-gradient(180deg,#ffc366,#ff974c);transform:translateY(1px);box-shadow:0 1px 0 #d96728}.practice-toggle:focus-visible{outline:3px solid rgba(109,87,235,.3);outline-offset:3px}
.question-entry{grid-template-columns:minmax(0,1fr) 168px;gap:14px;align-items:stretch}
.question-card textarea{min-height:106px;height:106px;padding:16px 17px;border:2px solid #dce6f6;border-radius:17px;background:#fcfdff;color:#253b69;font-size:15px;line-height:1.58;box-shadow:inset 0 1px 0 rgba(255,255,255,.95)}
.question-card textarea:focus{border-color:#9f8df3;box-shadow:0 0 0 4px rgba(109,87,235,.10)}
.question-actions{justify-content:center}.parse{min-height:58px;margin:0;border-radius:17px;background:linear-gradient(180deg,#846eff 0,#6d57eb 100%);box-shadow:0 7px 0 #5040bf;color:#fff;font-size:18px;font-weight:1000}.parse-result{margin:12px 2px 0;text-align:center;color:#8390a5;font-size:11px;line-height:1.45}.question-card #error{grid-column:2;margin:0;color:#d64c42;font-size:12px}
.practice-panel{grid-column:1/-1;display:grid;grid-template-columns:auto minmax(190px,1fr) minmax(150px,.7fr) auto auto;gap:12px;align-items:end;padding:13px 14px;border:1px solid #eadcff;border-radius:16px;background:linear-gradient(135deg,#faf7ff,#fffaf0);box-shadow:inset 0 1px 0 #fff}.practice-panel[hidden]{display:none!important}.practice-panel-copy{display:flex;flex-direction:column;gap:3px;align-self:center}.practice-panel-copy strong{color:#5642bb;font-size:14px}.practice-panel-copy span{color:#8490a3;font-size:10px}.practice-panel label{display:flex;min-width:0;flex-direction:column;gap:5px}.practice-panel label>span{color:#6f7890;font-size:10px;font-weight:900}.practice-panel select{width:100%;min-height:40px;padding:7px 34px 7px 11px;border:1px solid #d9d3f2;border-radius:11px;background:#fff;color:#2d3f69;font-size:13px;font-weight:800}.practice-panel button{min-height:40px;padding:7px 15px;border:0;border-radius:11px;background:#f08342;color:#fff;font-size:13px;font-weight:1000;cursor:pointer}.practice-panel #practiceClose{border:1px solid #dfe3ec;background:#fff;color:#778398}.parse-result.practice-ready{color:#b76625;font-weight:900}

.answer-card{margin-top:18px;padding:0;border:0;border-radius:0;background:transparent;box-shadow:none}.answer-card.is-empty{display:none}
.top{align-items:center;padding:0 16px 14px;border:0}.top small{display:block;color:#f08b4c;font-size:11px;font-weight:1000;letter-spacing:.11em}.top h2{margin:3px 0 0;color:#273c70;font-size:23px;line-height:1.25}
.learning-journey{position:relative;display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px;align-items:stretch}.journey-guide{position:absolute;top:-54px;left:50%;z-index:3;display:block;transform:translateX(-50%);padding:7px 18px;border:2px solid #eadfff;border-radius:999px;background:#fff;color:#765ee4;box-shadow:0 5px 12px rgba(80,62,174,.08)}.journey-guide>span{font-size:13px;font-weight:1000;white-space:nowrap}.journey-guide ol{display:none}
.learning-stage{display:flex;min-height:438px;flex-direction:column;gap:0;padding:0;border:1px solid #e3e7f1;border-radius:25px;background:#fff;box-shadow:var(--shadow);overflow:hidden}.observe-stage{background:#f6f1ff}.relationship-stage{background:#e8f7ff}.calculate-stage{background:#fff6c8}
.stage-head{display:flex;align-items:center;gap:10px;min-height:94px;padding:18px 20px 12px;border:0}.stage-number{width:38px;height:38px;border:0;border-radius:50%;background:#fff;color:#6952e2;font-size:17px;font-weight:1000;box-shadow:0 3px 8px rgba(85,61,187,.14)}.relationship-stage .stage-number{background:#fff;color:#4a93b9}.calculate-stage .stage-number{background:#fff;color:#d8852d}.stage-head h3{margin:0;color:var(--ink);font-size:25px;line-height:1.05;font-weight:1000}.stage-head p{margin:5px 0 0;color:#5d5f92;font-size:12px;font-weight:800;line-height:1.42}.relationship-stage .stage-head p{color:#4d7185}.calculate-stage .stage-head p{color:#8a7245}
.stage-content{display:flex;min-width:0;flex:1;flex-direction:column;padding:0 16px 16px}.observe-stage .stage-content,.relationship-stage .stage-content{padding-top:0}.calculate-stage .stage-content{padding-top:0}
.animation-controls{display:grid;grid-template-columns:auto auto minmax(0,1fr);gap:7px;margin:0 0 10px;padding:0;background:transparent;border:0}.animation-controls label,.animation-controls output{display:none}.animation-controls button{min-height:35px;padding:5px 10px;border:1px solid #d9ceff;border-radius:11px;background:#fff;color:#6048c9;font-size:11px;font-weight:1000}.animation-controls button:first-child{background:var(--violet);border-color:var(--violet);color:#fff}.animation-controls input{min-width:0;margin:0;accent-color:var(--violet)}
.motion-panel{display:flex;min-height:0;flex:1;flex-direction:column;margin:0;padding:11px;border:1px solid rgba(125,103,222,.20);border-radius:18px;background:#fff}.motion-heading{padding:0 3px 6px}.motion-heading strong{font-size:12px}.motion-heading span{font-size:10px}.motion-panel.train-lesson #motionSvg{border-radius:13px;background:#e9f8ff}.motion-panel #motionSvg{flex:1;min-height:165px;margin:0;border-radius:13px;background:#fbfcff}.motion-equation{min-height:1.5em;margin:7px 0 0;padding:8px 10px;border-radius:11px;background:#f4f1ff;color:#4c3bad;font-size:11px;text-align:center;line-height:1.42}
.relationship-stage #svg{display:block;flex:1;width:100%;min-height:214px;max-height:none;margin:0;border:1px solid rgba(74,163,203,.20);border-radius:18px;background:#fff}.events{display:none}
.steps{display:grid;grid-template-columns:1fr;gap:8px;margin:0}.step{min-height:0;grid-template-columns:29px 1fr;gap:8px;padding:10px 11px;border:1px solid rgba(202,161,55,.17);border-radius:13px;background:rgba(255,255,255,.78)}.step i{width:27px;height:27px;border-radius:50%;background:#7560e6;font-size:10px}.step:nth-child(3n+2) i{background:#f78345}.step:nth-child(3n) i{background:#62a482}.step small{font-size:10px;color:#897b5d}.step b{margin-top:2px;font-size:12px;line-height:1.42}.empty{padding:24px 12px;background:rgba(255,255,255,.65);font-size:12px}
.final-equation{margin-top:auto;padding:12px;border:1px solid #ffdcb3;border-radius:14px;background:rgba(255,255,255,.86)}.final-equation small{color:#d17831;font-size:10px}.final-equation>strong{margin-top:4px;color:#5f447e;font-size:14px;line-height:1.45}.equation-details{display:none}.final-answer{display:grid;grid-template-columns:auto 1fr;gap:8px;align-items:start;margin-top:11px;padding-top:10px;border-top:1px dashed #efd3aa}.final-answer span{padding:3px 8px;border-radius:999px;background:#765ee4;color:#fff;font-size:10px;font-weight:1000}.final-answer b{color:#43845f;font-size:15px;line-height:1.45}
.cheer-strip{display:flex;align-items:center;gap:16px;min-height:110px;margin-top:18px;padding:10px 28px 10px 16px;border:1px solid #e4e7f1;border-radius:24px;background:#fff;box-shadow:var(--shadow)}.cheer-strip[hidden]{display:none!important}.cheer-strip img{align-self:flex-end;width:94px;height:86px;object-fit:contain;object-position:center bottom}.cheer-strip div{flex:1;min-width:0}.cheer-strip strong{color:#725be5;font-size:21px;font-weight:1000}.cheer-strip p{margin:4px 0 0;color:#65738d;font-size:13px;font-weight:700}.cheer-strip>span{padding:10px 15px;border-radius:14px;background:#fff3d6;color:#d7822e;font-size:12px;font-weight:1000}
#motionSvg .motion-sprite{filter:drop-shadow(0 3px 3px rgba(39,54,96,.18))}

@media(max-width:1040px){
  .learning-journey{grid-template-columns:1fr;gap:14px}.journey-guide{position:static;justify-self:center;transform:none;margin:0 0 -3px}.learning-stage{min-height:0}.stage-head{min-height:0;padding:16px 18px 10px}.stage-content{min-height:320px}.relationship-stage #svg{min-height:275px}.steps{grid-template-columns:repeat(2,minmax(0,1fr))}.calculate-stage .stage-content{min-height:300px}
}
@media(max-width:820px){
  main{width:min(100% - 20px,680px);padding-top:10px}.site-header{min-height:103px;padding:9px 114px 9px 12px}.brand-kicker{margin-bottom:4px;font-size:10px}.site-header h1{font-size:clamp(21px,6.3vw,31px);line-height:1.04;white-space:nowrap}.site-header h1 em{display:inline;margin:0}.site-header small{margin-top:5px;font-size:11px}.mascot-corner{right:0;bottom:-2px}.mascot-corner img{width:105px;height:96px}.mascot-bubble{display:none}
  .question-card{grid-template-columns:1fr;gap:12px;padding:16px;border-radius:20px}.question-copy{padding:0;border:0}.question-copy p{max-width:none;margin:8px 0 0;font-size:12px}.section-title span{width:34px;height:34px;border-radius:11px}.section-title span img{width:28px;height:28px}.section-title h2{font-size:19px}.practice-toggle{min-height:31px;flex:none;margin-left:auto;padding:6px 10px;font-size:12px}.question-entry{grid-template-columns:1fr;gap:10px}.question-card textarea{height:125px;min-height:125px;padding:13px;font-size:14px}.question-actions{display:grid;grid-template-columns:142px 1fr;gap:10px;align-items:center}.parse{min-height:48px;border-radius:14px;font-size:16px}.parse-result{margin:0;text-align:left}.question-card #error{grid-column:auto}.practice-panel{grid-template-columns:repeat(2,minmax(0,1fr)) auto auto}.practice-panel-copy{grid-column:1/-1}
  .answer-card{margin-top:14px}.top{display:block;padding:0 4px 11px}.top h2{font-size:21px}.top strong{display:block;max-width:none;margin-top:7px;font-size:15px}.learning-journey{gap:12px}.learning-stage{border-radius:20px}.stage-head{padding:15px 15px 9px}.stage-number{width:33px;height:33px;font-size:14px}.stage-head h3{font-size:21px}.stage-head p{font-size:11px}.stage-content{min-height:286px;padding:0 12px 12px}.motion-panel #motionSvg{min-height:148px}.relationship-stage #svg{min-height:210px}.steps{grid-template-columns:1fr}.calculate-stage .stage-content{min-height:0}.cheer-strip{min-height:87px;gap:9px;margin-top:13px;padding:8px 12px;border-radius:18px}.cheer-strip img{width:62px;height:67px}.cheer-strip strong{font-size:17px}.cheer-strip p{font-size:11px;line-height:1.4}.cheer-strip>span{display:none}
}
@media(max-width:430px){.site-header{padding-right:88px}.mascot-corner img{width:84px;height:82px}.site-header h1{font-size:clamp(19px,6.3vw,23px);letter-spacing:0}.question-actions{grid-template-columns:1fr}.parse-result{text-align:center}.practice-panel{grid-template-columns:1fr 1fr}.practice-panel label{grid-column:1/-1}.practice-panel button{min-height:44px}.journey-guide>span{display:inline;font-size:11px}.motion-panel{padding:8px}.stage-content{padding-left:10px;padding-right:10px}}
@media(max-width:350px){.site-header{padding-right:72px}.mascot-corner img{width:70px;height:70px}.site-header h1{font-size:19px}.brand-kicker{font-size:9px}.site-header small{font-size:10px}}

/* 拍照识题：与文字输入共用同一条解题流水线 */
.question-input-stack{display:flex;min-width:0;flex-direction:column;gap:8px}
.photo-question-tools{display:flex;min-height:34px;align-items:center;gap:9px;padding:0 3px}
.photo-question-button,.photo-question-tools button{display:inline-flex;min-height:32px;align-items:center;justify-content:center;padding:6px 12px;border:1px solid #d8d0ff;border-radius:11px;background:#f4f1ff;color:#5b47c5;font-size:12px;font-weight:1000;cursor:pointer}
.photo-question-button:hover,.photo-question-tools button:hover{background:#ebe6ff}
.photo-question-tools>span{min-width:0;flex:1;color:#8390a5;font-size:10px;line-height:1.35}
.photo-question-tools button{border-color:#e6e9ef;background:#fff;color:#7d8798}
.photo-preview{display:flex;align-items:center;gap:10px;padding:8px 10px;border:1px solid #dce6f6;border-radius:13px;background:#f7fbff}
.photo-preview img{width:70px;height:48px;border-radius:8px;object-fit:cover;background:#e9eef5}
.photo-preview div{display:flex;min-width:0;flex:1;flex-direction:column;gap:3px}.photo-preview strong{color:#334b77;font-size:11px}.photo-preview span{color:#6d57eb;font-size:10px;font-weight:800}
.photo-number-check{display:flex;align-items:center;gap:9px;padding:8px 10px;border:1px solid #ffe0a8;border-radius:12px;background:#fff9e9}.photo-number-check>strong{flex:none;color:#bd6b22;font-size:10px}.photo-number-check>div{display:flex;min-width:0;flex-wrap:wrap;gap:5px}.photo-number-check span{padding:3px 7px;border-radius:8px;background:#ffecb8;color:#6a481b;font-size:11px;font-weight:1000}
.photo-number-check span.is-warning{border:1px dashed #ef8f35;background:#fff3d4;color:#a34f14}
@media(max-width:430px){.photo-question-tools{align-items:flex-start;flex-wrap:wrap}.photo-question-tools>span{flex-basis:150px;padding-top:7px}.photo-question-button{min-height:38px;padding:8px 14px}.photo-preview img{width:64px;height:48px}.photo-number-check{align-items:flex-start;flex-direction:column;gap:6px}}

/* 纵向阅读版：每个步骤独占整行，让动画、图解和算式都拥有足够画布。 */
.learning-journey{grid-template-columns:minmax(0,1fr);gap:18px}
.learning-stage{min-height:0;overflow:visible}
.stage-head{min-height:0;flex-direction:row;justify-content:flex-start;align-items:center;gap:12px;padding:16px 20px 12px}
.stage-head>div{display:flex;align-items:center;min-width:0}
.stage-head p{display:none}
.stage-number{width:40px;height:40px;font-size:17px}
.stage-head h3{margin:0;font-size:24px;line-height:1.15}
.stage-content,.calculate-stage .stage-content{min-height:0;padding:0 20px 20px}
.motion-heading strong{font-size:17px}.motion-heading span{font-size:14px}
.motion-equation{padding:11px 14px;font-size:17px;line-height:1.55}
.animation-controls button{min-height:42px;padding:8px 15px;font-size:14px}
.animation-controls output{font-size:13px}
.motion-panel #motionSvg{min-height:0}
.relationship-stage #svg{
  /* 关系图的高度由 SVG 的动态 viewBox 决定。不能作为可压缩的 flex 项，
     否则节点多时仍会被挤回有限高度。 */
  flex:0 0 auto;
  width:100%;
  height:auto;
  min-height:0;
  max-height:none;
}
.steps{grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:12px}
.step{padding:15px 16px}.step small{font-size:13px}.step b{font-size:16px;line-height:1.55}
.final-equation{padding:17px 18px}.final-equation small{font-size:12px}.final-equation>strong{font-size:19px;line-height:1.55}.final-answer b{font-size:19px}
#motionSvg text[font-size="8"],#motionSvg text[font-size="9"],#svg text[font-size="8"],#svg text[font-size="9"]{font-size:11px!important}
#motionSvg text[font-size="10"],#svg text[font-size="10"]{font-size:12px!important}
#motionSvg text[font-size="11"],#svg text[font-size="11"]{font-size:13px!important}
#motionSvg text[font-size="13"],#svg text[font-size="13"]{font-size:15px!important}
.photo-preview[hidden],.photo-number-check[hidden],#photoClear[hidden]{display:none!important}
@media(max-width:820px){.stage-head{padding:14px 14px 10px}.stage-number{width:34px;height:34px;font-size:15px}.stage-head h3{font-size:21px}.stage-content,.calculate-stage .stage-content{padding:0 12px 14px}.motion-heading strong{font-size:15px}.motion-heading span{font-size:12px}.motion-equation{font-size:14px}.steps{grid-template-columns:1fr}.step small{font-size:12px}.step b{font-size:15px}.final-equation>strong{font-size:17px}}

/* 标题栏题型导航：电脑端居中弹窗，手机端底部抽屉。 */
.brand-subline{display:flex;align-items:center;gap:12px;margin-top:8px}
.site-header .brand-subline small{display:block;margin:0}
.capability-trigger{
  display:inline-flex;min-height:34px;align-items:center;gap:7px;padding:6px 8px 6px 11px;
  border:1.5px solid #d9ceff;border-radius:999px;background:#fff;color:#5f49c8;
  font-size:12px;font-weight:1000;line-height:1;cursor:pointer;box-shadow:0 5px 14px rgba(86,66,181,.10);
  transition:transform .18s ease,box-shadow .18s ease,border-color .18s ease;
}
.capability-trigger:hover{transform:translateY(-2px);border-color:#9d8af1;box-shadow:0 8px 18px rgba(86,66,181,.16)}
.capability-trigger:focus-visible,.capability-close:focus-visible{outline:4px solid rgba(109,87,235,.22);outline-offset:2px}
.capability-trigger-icon{font-size:16px;line-height:1}
.capability-trigger strong{display:grid;min-width:31px;height:23px;place-items:center;padding:0 6px;border-radius:999px;background:#e8f79c;color:#47651d;font-size:11px}

.capability-layer[hidden]{display:none!important}
.capability-layer{position:fixed;inset:0;z-index:2000;display:grid;place-items:center;padding:24px}
.capability-backdrop{position:absolute;inset:0;width:100%;height:100%;padding:0;border:0;background:rgba(31,40,72,.48);cursor:default;backdrop-filter:blur(7px)}
.capability-sheet{
  position:relative;width:min(920px,100%);max-height:calc(100dvh - 48px);overflow:auto;
  padding:27px;border:1px solid rgba(219,226,240,.92);border-radius:30px;background:#fffdf8;
  box-shadow:0 26px 70px rgba(31,40,72,.25);animation:capability-pop .22s ease-out both;
}
.capability-close{position:absolute;top:18px;right:18px;z-index:2;display:grid;width:38px;height:38px;place-items:center;padding:0;border:1px solid #e2e6ee;border-radius:50%;background:#fff;color:#6f7c91;font-size:25px;line-height:1;cursor:pointer;box-shadow:0 4px 12px rgba(34,50,87,.08)}
.capability-close:hover{background:#f4f1ff;color:#6049cd}
.capability-heading{display:grid;grid-template-columns:58px minmax(0,1fr) auto;gap:15px;align-items:center;padding:2px 52px 21px 2px}
.capability-heading-icon{display:grid;width:58px;height:58px;place-items:center;border-radius:20px;background:linear-gradient(145deg,#eae5ff,#f7f5ff);font-size:30px;box-shadow:inset 0 0 0 1px #ded5ff}
.capability-heading p{margin:0 0 3px;color:#ef8848;font-size:11px;font-weight:1000;letter-spacing:.12em}
.capability-heading h2{margin:0;color:#243c72;font-size:clamp(24px,3vw,34px);font-weight:1000;line-height:1.18}
.capability-heading div>span{display:block;margin-top:7px;color:#748198;font-size:13px;font-weight:750;line-height:1.5}
.capability-heading>strong{align-self:start;margin-top:5px;padding:9px 13px;border:1px solid #d7edba;border-radius:14px;background:#f2fbdc;color:#54752a;font-size:13px;white-space:nowrap}
.capability-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}
.capability-card{--cap:#6d57eb;--cap-bg:#f3f0ff;display:flex;min-width:0;align-items:flex-start;gap:12px;padding:16px;border:1px solid #e5e8ef;border-radius:19px;background:#fff;box-shadow:0 5px 15px rgba(35,57,93,.05)}
.capability-card:hover{border-color:color-mix(in srgb,var(--cap) 32%,#e5e8ef);transform:translateY(-1px)}
.capability-icon{display:grid;flex:0 0 auto;width:43px;height:43px;place-items:center;border-radius:14px;background:var(--cap-bg);font-size:22px}
.capability-card h3{margin:1px 0 6px;color:var(--cap);font-size:16px;font-weight:1000;line-height:1.25}
.capability-card p{margin:0;color:#68768d;font-size:12px;font-weight:750;line-height:1.6}
.capability-orange{--cap:#e46e38;--cap-bg:#fff0e7}.capability-blue{--cap:#3880b8;--cap-bg:#eaf7ff}.capability-green{--cap:#438361;--cap-bg:#eaf7ee}.capability-yellow{--cap:#ad7716;--cap-bg:#fff5cc}.capability-pink{--cap:#c65e82;--cap-bg:#fff0f5}
.capability-note{display:flex;align-items:flex-start;gap:10px;margin-top:15px;padding:12px 15px;border:1px dashed #e5c26b;border-radius:15px;background:#fff9e7}
.capability-note>span{font-size:18px}.capability-note p{margin:0;color:#705f3d;font-size:12px;font-weight:750;line-height:1.55}.capability-note strong{color:#a46c1c}
body.capability-open{overflow:hidden}
@keyframes capability-pop{from{opacity:0;transform:translateY(12px) scale(.98)}to{opacity:1;transform:none}}

@media(max-width:820px){
  .brand-subline{gap:7px;margin-top:5px}
  .capability-trigger{min-height:29px;padding:4px 6px 4px 8px;font-size:10px;box-shadow:none}
  .capability-trigger-icon{font-size:13px}.capability-trigger strong{min-width:25px;height:19px;padding:0 4px;font-size:9px}
  .capability-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
}
@media(max-width:600px){
  .site-header{min-height:124px}
  .brand-subline{align-items:flex-start;flex-direction:column;gap:6px}
  .capability-layer{align-items:end;padding:0}
  .capability-sheet{width:100%;max-height:88dvh;padding:20px 16px calc(18px + env(safe-area-inset-bottom));border-radius:27px 27px 0 0;animation-name:capability-rise}
  .capability-close{top:15px;right:15px;width:36px;height:36px}
  .capability-heading{grid-template-columns:46px minmax(0,1fr);gap:11px;padding:1px 42px 16px 1px}
  .capability-heading-icon{width:46px;height:46px;border-radius:15px;font-size:24px}
  .capability-heading h2{font-size:22px}.capability-heading div>span{font-size:11px}.capability-heading>strong{display:none}
  .capability-grid{grid-template-columns:1fr;gap:9px}
  .capability-card{align-items:center;gap:10px;padding:12px 13px;border-radius:16px}
  .capability-icon{width:38px;height:38px;border-radius:12px;font-size:19px}
  .capability-card h3{margin:0 0 3px;font-size:15px}.capability-card p{font-size:11px;line-height:1.45}
  .capability-note{margin-top:11px;padding:10px 12px}.capability-note p{font-size:11px}
  @keyframes capability-rise{from{opacity:.4;transform:translateY(40px)}to{opacity:1;transform:none}}
}
@media(max-width:350px){.capability-trigger{font-size:9px}.capability-trigger-icon{display:none}}
@media(prefers-reduced-motion:reduce){.capability-sheet{animation:none}.capability-trigger{transition:none}}

/* 多图图解系统。旧单图渲染仍保留，可用 ?singleDiagram=1 立即退回。 */
.diagram-sequence[hidden],.diagram-page-caption[hidden]{display:none!important}
.diagram-sequence{margin:0 0 12px;padding:11px 12px;border:1px solid #cfe2ee;border-radius:15px;background:rgba(255,255,255,.82)}
.diagram-sequence-topline{display:flex;align-items:center;justify-content:space-between;gap:12px}
.diagram-sequence-topline>div:first-child{display:flex;align-items:center;gap:9px}
.diagram-sequence-topline span{color:#3f86ab;font-size:13px;font-weight:1000}
.diagram-sequence-topline strong{padding:4px 8px;border-radius:999px;background:#eaf7ff;color:#345d7a;font-size:11px;white-space:nowrap}
.diagram-swipe-hint{display:none;color:#76879a;font-size:9px;font-weight:800;white-space:nowrap}
.diagram-sequence-arrows{display:flex;gap:6px}
.diagram-sequence-arrows button{display:grid;width:32px;height:32px;place-items:center;padding:0;border:1px solid #ccdfeb;border-radius:10px;background:#fff;color:#315d78;font-size:17px;font-weight:1000;cursor:pointer}
.diagram-sequence-arrows button:hover:not(:disabled){border-color:#68a9cb;background:#edf9ff}.diagram-sequence-arrows button:disabled{opacity:.32;cursor:default}
.diagram-tabs{display:flex;gap:7px;margin-top:10px;overflow-x:auto;padding:1px 1px 4px;scrollbar-width:thin}
.diagram-tabs button{display:inline-flex;min-height:34px;flex:0 0 auto;align-items:center;gap:6px;padding:6px 11px;border:1px solid #dae5ec;border-radius:11px;background:#fff;color:#64768a;font-size:11px;font-weight:900;white-space:nowrap;cursor:pointer}
.diagram-tabs button i{display:grid;width:20px;height:20px;place-items:center;border-radius:50%;background:#edf1f5;color:#64768a;font-style:normal;font-size:9px}
.diagram-tabs button.active{border-color:#806aee;background:#f2efff;color:#5844c5;box-shadow:0 3px 9px rgba(88,68,197,.10)}
.diagram-tabs button.active i{background:#6d57eb;color:#fff}
.diagram-canvas{position:relative;min-width:0;overflow:hidden;border-radius:18px;background:#fff}
.diagram-canvas #svg{transition:opacity .16s ease}
.diagram-page-caption{display:grid;grid-template-columns:38px minmax(0,1fr);gap:11px;align-items:start;margin-top:10px;padding:12px 14px;border:1px solid #dde7ee;border-radius:14px;background:#f8fbfd}
.diagram-page-caption>span{display:grid;width:34px;height:34px;place-items:center;border-radius:50%;background:#6d57eb;color:#fff;font-size:11px;font-weight:1000}
.diagram-page-caption strong{display:block;color:#284b67;font-size:14px;font-weight:1000}.diagram-page-caption p{margin:4px 0 0;color:#68798d;font-size:12px;font-weight:750;line-height:1.55}
.diagram-page-caption.is-overview{border-color:#eadbbd;background:#fffaf0}.diagram-page-caption.is-overview>span{background:#e18b39}.diagram-page-caption.is-overview strong{color:#8a5b25}
@media(max-width:600px){
  .diagram-sequence{padding:9px 10px;border-radius:13px}.diagram-sequence-topline>div:first-child{flex-wrap:wrap;gap:5px 7px}.diagram-sequence-topline span{font-size:12px}.diagram-swipe-hint{display:inline}.diagram-sequence-arrows button{width:35px;height:35px}
  .diagram-tabs button{min-height:36px;padding:7px 10px;font-size:10px}.diagram-page-caption{grid-template-columns:34px minmax(0,1fr);padding:10px 11px}.diagram-page-caption>span{width:31px;height:31px}.diagram-page-caption strong{font-size:13px}.diagram-page-caption p{font-size:11px}
  .diagram-canvas.is-multi{overflow-x:auto;overscroll-behavior-inline:contain;scrollbar-width:thin;scrollbar-color:#a998ef #edf2f6}
  .diagram-canvas.is-multi #svg{width:680px;max-width:none;touch-action:pan-x pan-y}
}
@media(prefers-reduced-motion:reduce){.diagram-canvas #svg{transition:none}}

/* 深度迭代：把阅读重心留给运动、图解和算式。 */
.journey-guide{display:none!important}
.top{padding:0 4px 13px}
.top small{display:inline-flex;width:fit-content;align-items:center;min-height:24px;padding:4px 9px;border:1px solid #ffd6ad;border-radius:999px;background:#fff7ea;color:#d97834;font-size:11px;letter-spacing:.04em;box-shadow:0 3px 8px rgba(216,120,52,.08)}
.top h2{margin-top:8px;font-size:25px}
.learning-stage{box-shadow:0 9px 20px rgba(67,75,142,.08)}
.animation-controls{grid-template-columns:auto auto minmax(120px,1fr) minmax(180px,auto);align-items:center;gap:9px;margin:0 0 12px;padding:9px 10px;border:1px solid rgba(125,103,222,.13);border-radius:14px;background:rgba(255,255,255,.62)}
.animation-controls label{display:none}
.animation-controls input{grid-column:3;min-width:110px}
.animation-controls output{display:block;grid-column:4;min-width:0;max-width:300px;overflow:hidden;padding:7px 10px;border:1px solid #e3def8;border-radius:10px;background:#fff;color:#5e5793;font-size:12px;font-weight:900;line-height:1.25;text-align:left;text-overflow:ellipsis;white-space:nowrap}
.motion-equation{border:1px solid rgba(122,103,214,.09);box-shadow:inset 0 1px 0 rgba(255,255,255,.9)}
.diagram-page-caption{box-shadow:0 4px 11px rgba(59,87,110,.05)}
@media(max-width:820px){
  .top{padding:0 2px 10px}.top h2{margin-top:7px;font-size:22px}
  .animation-controls{grid-template-columns:auto auto minmax(0,1fr);gap:8px}
  .animation-controls input{grid-column:1/-1}
  .animation-controls output{grid-column:1/-1;max-width:none;font-size:12px}
}
@media(max-width:430px){
  .top small{min-height:22px;padding:3px 8px;font-size:10px}
  .animation-controls{padding:8px}.animation-controls button{min-height:40px;padding:7px 11px;font-size:13px}
  .animation-controls output{padding:7px 9px;white-space:normal}
}

/* 当前公开版本：页脚保持克制，不抢解题内容的阅读重心。 */
.site-version{
  width:min(1440px,calc(100% - 32px));
  margin:0 auto 24px;
  color:#93a0b5;
  font-size:12px;
  font-weight:800;
  letter-spacing:.08em;
  text-align:center;
}
.site-version a{color:inherit;text-decoration:none}
.site-version a:hover{text-decoration:underline;color:#6277df}
@media(max-width:820px){
  .site-version{width:min(680px,calc(100% - 20px));margin-bottom:18px;font-size:11px}
}
@media(max-width:350px){.site-version{width:calc(100% - 14px)}}