:root{--ink:#173e4d;--muted:#66808a;--teal:#2f829c;--teal-dark:#216477;--blue:#315fc7;--orange:#e98a20;--green:#278b68;--red:#dc5b4b;--purple:#7750c9;--line:#c8dadd;--paper:#fff;--page:#f1f7f7;--shadow:0 16px 44px rgba(31,71,82,.12)}
*{box-sizing:border-box}
body{margin:0;min-width:320px;color:var(--ink);background:linear-gradient(rgba(47,130,156,.035) 1px,transparent 1px),linear-gradient(90deg,rgba(47,130,156,.035) 1px,transparent 1px),var(--page);background-size:32px 32px;font-family:"Microsoft YaHei","PingFang SC","Noto Sans SC",system-ui,sans-serif}
button,input{font:inherit}button{touch-action:manipulation}
.page-shell{width:min(1900px,calc(100% - 24px));margin:0 auto;padding:30px 0 52px}
.page-header{display:flex;align-items:flex-end;justify-content:space-between;gap:28px;margin-bottom:22px;padding:0 4px}.eyebrow{display:block;color:var(--orange);font-size:15px;font-weight:850;letter-spacing:.12em;margin-bottom:8px}h1{font-size:clamp(31px,3.4vw,50px);line-height:1.08;margin:0 0 10px;letter-spacing:-.035em}.page-header p{margin:0;color:var(--muted);font-size:17px;line-height:1.6}.back-link{flex:0 0 auto;padding:10px 15px;border:1px solid var(--line);border-radius:999px;background:#fff;color:var(--teal-dark);font-size:14px;font-weight:850;text-decoration:none}
.page-tools{align-self:flex-start;margin-left:auto;flex:0 0 auto}.zoom-control{display:grid;grid-template-columns:34px 54px 34px;align-items:center;padding:3px;border:1px solid #bfd0d3;border-radius:999px;background:rgba(255,255,255,.88);box-shadow:0 5px 16px rgba(31,71,82,.08)}.zoom-control button{height:30px;border:0;border-radius:999px;background:transparent;color:#315868;cursor:pointer;font-size:1.1rem;font-weight:850;line-height:1}.zoom-control button:hover{background:#e4edef}.zoom-control button:disabled{opacity:.35;cursor:default}.zoom-control .zoom-value{font-size:.76rem;font-variant-numeric:tabular-nums}
.structure-panel,.conversion-section,.summary-strip{background:var(--paper);border:1px solid rgba(152,184,190,.68);box-shadow:var(--shadow);border-radius:22px}.structure-panel,.conversion-section{padding:22px}.conversion-section{margin-top:20px}.section-heading{display:flex;align-items:center;gap:12px}.section-heading.compact{margin-bottom:16px}.step-number{display:grid;place-items:center;flex:0 0 auto;width:40px;height:40px;border-radius:12px;background:#fff1dd;color:var(--orange);font-size:14px;font-weight:900}h2{font-size:22px;margin:0}.section-heading p{margin:4px 0 0;color:var(--muted);font-size:14px}.structure-heading-actions{display:flex;align-items:center;gap:10px;margin-left:auto}.movement-spec{padding:9px 13px;border-radius:12px;background:#e9f4f5;text-align:right}.movement-spec span{display:block;color:var(--muted);font-size:12px}.movement-spec strong{display:block;margin-top:3px;color:var(--teal-dark);font-size:16px;font-variant-numeric:tabular-nums}
.structure-control-bar{display:grid;grid-template-columns:minmax(390px,1.5fr) minmax(250px,.9fr) minmax(190px,.65fr) minmax(290px,1fr);gap:10px;margin-top:16px}.structure-current-control,.direction-control,.scale-control,.deflection-relation{min-width:0;padding:12px 14px;border:1px solid #d5e4e6;border-radius:14px;background:#f4f9f9}.structure-current-control{display:grid;grid-template-columns:1fr auto;align-items:center;gap:8px 12px}.structure-current-control>span,.direction-control>span,.scale-control>span,.deflection-relation>span{color:var(--muted);font-size:14px;font-weight:800}.structure-current-control strong{font-size:16px;color:var(--teal-dark);font-variant-numeric:tabular-nums}.current-steps{display:grid;grid-template-columns:repeat(6,1fr);grid-column:1/-1;gap:5px}.current-steps button{min-width:0;padding:7px 3px;border:1px solid #c8dadd;border-radius:8px;background:#fff;color:var(--muted);font-size:13px;font-weight:850;font-variant-numeric:tabular-nums;cursor:pointer}.current-steps button.active{border-color:var(--teal);background:var(--teal);box-shadow:0 3px 9px rgba(47,130,156,.2);color:#fff}.direction-control{display:flex;align-items:center;justify-content:space-between;gap:12px}.direction-control>div{display:flex;padding:3px;border-radius:10px;background:#e5eeee}.direction-control button{min-width:90px;padding:7px 10px;border:0;border-radius:8px;background:transparent;color:var(--muted);font-size:13px;font-weight:900;white-space:nowrap;cursor:pointer}.direction-control button.active{background:var(--teal);box-shadow:0 3px 10px rgba(47,130,156,.22);color:#fff}.direction-control button#reverseCurrentButton.active{background:var(--purple);box-shadow:0 3px 10px rgba(119,80,201,.22)}.scale-control{display:grid;grid-template-columns:1fr;gap:6px}.scale-control small{color:var(--muted);font-size:12px;line-height:1.35}.switch-button{display:flex;align-items:center;gap:8px;padding:0;border:0;background:transparent;color:var(--ink);font-size:13px;font-weight:850;cursor:pointer}.switch-button i{position:relative;width:38px;height:22px;border-radius:999px;background:#b8c7cb;transition:.18s}.switch-button i::after{content:"";position:absolute;top:3px;left:3px;width:16px;height:16px;border-radius:50%;background:#fff;box-shadow:0 1px 4px rgba(23,62,77,.25);transition:.18s}.switch-button.active i{background:var(--green)}.switch-button.active i::after{transform:translateX(16px)}.deflection-relation{display:grid;grid-template-columns:auto 1fr;align-items:center;gap:4px 10px;background:#fffaf2;border-color:#efdbbd}.deflection-relation strong{color:#9a5a12;font-size:15px}.deflection-relation small{grid-column:2;color:var(--muted);font-size:12px}.center-zero-note{margin:9px 3px 0;color:#6b7e84;font-size:12px;line-height:1.55}
.current-steps{position:relative;display:grid;grid-template-columns:repeat(6,1fr);grid-column:1/-1;gap:0;padding:0 7px}.current-steps::before{content:"";position:absolute;top:7px;left:12px;right:12px;height:2px;background:#bfd0d3}.current-steps button{position:relative;display:grid;place-items:center;gap:3px;min-width:0;padding:0;border:0;background:transparent;color:var(--muted);font-size:12px;font-weight:850;font-variant-numeric:tabular-nums;cursor:pointer}.current-steps button i{position:relative;z-index:1;width:14px;height:14px;border:3px solid #fff;border-radius:50%;background:#9cb0b5;box-shadow:0 0 0 1px #9cb0b5;transition:.15s}.current-steps button small{font-size:11px}.current-steps button.active{border:0;background:transparent;box-shadow:none;color:var(--teal-dark)}.current-steps button.active i{background:var(--teal);box-shadow:0 0 0 2px var(--teal);transform:scale(1.08)}.structure-current-control>input{grid-column:1/-1;width:100%;margin:0;accent-color:var(--teal);cursor:pointer}
.structure-layout{display:grid;grid-template-columns:minmax(0,1fr) 310px;gap:15px;margin-top:16px}.structure-canvas-wrap{position:relative;min-width:0;overflow-x:auto;overflow-y:hidden;border:1px solid var(--line);border-radius:17px;background:#f8fbfb}.structure-layout canvas{display:block;width:100%;height:auto;aspect-ratio:1160/610}.structure-notes{display:grid;gap:9px}.structure-notes div{padding:13px 14px;border:1px solid #d7e4e6;border-radius:14px;background:#f6fafa}.structure-notes b,.structure-notes span{display:block}.structure-notes b{font-size:15px}.structure-notes span{margin-top:5px;color:var(--muted);font-size:13px;line-height:1.55}
.conversion-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.conversion-card{min-width:0;padding:18px;border:1px solid #cedfe1;border-radius:19px;background:#fbfdfd}.ammeter-card{box-shadow:inset 0 4px 0 var(--blue)}.voltmeter-card{box-shadow:inset 0 4px 0 var(--orange)}.card-header{display:flex;justify-content:space-between;align-items:flex-start;gap:14px}.card-actions{display:flex;align-items:center;gap:10px}.card-kicker{display:block;color:var(--blue);font-size:12px;font-weight:900;letter-spacing:.11em}.voltmeter-card .card-kicker{color:var(--orange)}h3{margin:4px 0 6px;font-size:22px}.card-header p{max-width:500px;margin:0;color:var(--muted);font-size:14px;line-height:1.55}.shell-button{flex:0 0 auto;display:flex;align-items:center;gap:7px;padding:9px 11px;border:1px solid #b9ced2;border-radius:11px;background:#fff;color:var(--teal-dark);font-size:13px;font-weight:850;cursor:pointer}.shell-button span{font-size:18px}.shell-button.open{border-color:var(--green);background:#eaf6f1;color:#1e7658}.equivalent-toggle{padding:9px 11px;border:1px solid #c9dadc;border-radius:11px;background:#fff}.equivalent-toggle.active{border-color:var(--green);background:#eaf6f1;color:#1e7658}
.conversion-workspace{display:grid;gap:12px}.conversion-controls,.conversion-visual{min-width:0}.meter-stage{position:relative;margin-top:0;overflow-x:auto;overflow-y:hidden;border:1px solid var(--line);border-radius:16px;background:#f5f9f9}.visual-toolbar{position:absolute;z-index:3;top:6%;left:50%;display:flex;align-items:center;justify-content:center;transform:translateX(-50%)}.visual-toolbar .shell-button{min-width:148px;justify-content:center;background:rgba(255,255,255,.96);box-shadow:0 5px 14px rgba(31,71,82,.12)}.meter-stage canvas{display:block;width:100%;height:auto;aspect-ratio:760/500}.state-pill{position:absolute;left:14px;bottom:12px;padding:8px 13px;border-radius:999px;background:rgba(255,255,255,.94);border:1px solid #d2e0e2;color:var(--muted);font-size:16px;font-weight:800}.state-pill.open{color:#1f7759;border-color:#b8dccd;background:rgba(239,250,245,.95)}.structure-canvas-wrap .state-pill{max-width:245px;border-radius:18px;line-height:1.35;white-space:normal}.meter-stage .state-pill{position:static;display:inline-block;margin:7px 12px 11px}
.control-grid{display:grid;grid-template-columns:1fr;gap:10px;margin-top:12px}.control-grid label{display:grid;grid-template-columns:1fr auto;gap:7px 9px;padding:11px 12px;border-radius:13px;background:#f2f7f7;border:1px solid #d7e4e6}.control-grid span{color:var(--muted);font-size:13px;font-weight:750}.control-grid strong{font-size:14px;font-variant-numeric:tabular-nums}.control-grid input{grid-column:1/-1;width:100%;accent-color:var(--blue)}.voltmeter-card .control-grid input{accent-color:var(--orange)}
.data-grid{display:grid;grid-template-columns:1fr;gap:8px;margin-top:10px}.data-grid div{padding:10px 11px;border:1px solid #d7e4e6;border-radius:12px;background:#fff}.data-grid span,.formula-card>span{display:block;color:var(--muted);font-size:12px}.data-grid strong{display:block;margin-top:6px;font-size:15px;font-variant-numeric:tabular-nums}.formula-card{display:grid;grid-template-columns:auto 1fr 1fr;align-items:center;gap:8px 13px;margin-top:10px;padding:11px 13px;border-radius:13px;background:#eaf2fa;border:1px solid #cbdbea}.voltmeter-card .formula-card{background:#fff5e7;border-color:#efd9b8}.formula-card>span{grid-row:1/3;font-weight:900;letter-spacing:.08em}.formula-card strong{font-size:15px;color:#255f9d}.voltmeter-card .formula-card strong{color:#a55c0b}.formula-card small{grid-column:2/-1;color:var(--muted);font-size:12px;line-height:1.45}
.full-scale-card{margin-top:10px;overflow:hidden;border:1px solid #d7e4e6;border-radius:13px;background:#fff}.full-scale-heading{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:9px 11px;background:#f2f7f7}.full-scale-heading strong{font-size:16px}.full-scale-heading span{color:var(--muted);font-size:14px}.table-scroll{overflow-x:auto}.full-scale-card table{width:100%;border-collapse:collapse;min-width:500px;font-size:16px;font-variant-numeric:tabular-nums}.full-scale-card th,.full-scale-card td{padding:9px 11px;border-top:1px solid #e3ecee;text-align:center;white-space:nowrap}.full-scale-card thead th{color:var(--muted);font-weight:800;background:#fbfdfd}.full-scale-card tbody th{color:var(--ink);text-align:left}.full-scale-card output{font:inherit;font-weight:850}
.summary-strip{display:grid;grid-template-columns:1fr auto 1fr 2fr;align-items:center;gap:15px;margin-top:20px;padding:18px 22px}.summary-strip>div:not(.divider-arrow){padding:10px 13px;border-radius:13px;background:#f4f8f8}.summary-strip span,.summary-strip small{display:block;color:var(--muted);font-size:12px}.summary-strip strong{display:block;margin:5px 0;font-size:18px}.divider-arrow{color:var(--orange);font-size:26px;font-weight:900}.summary-strip p{margin:0;color:var(--muted);font-size:14px;line-height:1.6}.summary-strip p sub{color:var(--ink);font-weight:800}
button:focus-visible,input:focus-visible,a:focus-visible{outline:3px solid rgba(233,138,32,.42);outline-offset:3px}
@media(max-width:1120px){.structure-control-bar{grid-template-columns:1fr 1fr}.deflection-relation{grid-column:auto}.structure-layout{grid-template-columns:1fr}.structure-notes{grid-template-columns:repeat(2,1fr)}.conversion-grid{grid-template-columns:1fr}.summary-strip{grid-template-columns:1fr auto 1fr}.summary-strip p{grid-column:1/-1}}
@media(max-width:680px){.page-shell{width:calc(100% - 18px);padding-top:18px}.page-header{align-items:flex-start;flex-direction:column}.page-tools{margin-left:0}.structure-panel,.conversion-section{padding:14px;border-radius:17px}.section-heading{align-items:flex-start;flex-wrap:wrap}.structure-heading-actions{width:100%;align-items:stretch;flex-direction:column;margin-left:0}.movement-spec{text-align:left}.structure-control-bar{grid-template-columns:1fr}.deflection-relation{grid-column:auto}.direction-control{align-items:flex-start;flex-direction:column}.direction-control>div{width:100%}.direction-control button{flex:1}.deflection-relation{grid-template-columns:1fr}.deflection-relation small{grid-column:auto}.structure-notes{grid-template-columns:1fr}.structure-layout canvas{width:820px;max-width:none}.card-header,.card-actions{width:100%;flex-direction:column}.shell-button,.equivalent-toggle{width:100%;justify-content:center}.meter-stage canvas{width:620px;max-width:none}.control-grid,.data-grid{grid-template-columns:1fr}.full-scale-heading{align-items:flex-start;flex-direction:column}.formula-card{grid-template-columns:1fr}.formula-card>span{grid-row:auto}.formula-card small{grid-column:auto}.summary-strip{grid-template-columns:1fr;padding:14px}.divider-arrow{display:none}.summary-strip p{grid-column:auto}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}

/* 教学操作布局：左侧集中控制，右侧固定观察图 */
@media(min-width:821px){
  .structure-panel{display:grid;grid-template-columns:minmax(250px,290px) minmax(0,1fr);grid-template-areas:"heading heading" "controls canvas" "note canvas" "notes notes";gap:12px 18px}
  .structure-panel>.section-heading{grid-area:heading;flex-wrap:wrap}
  .structure-control-bar{grid-area:controls;grid-template-columns:1fr;margin-top:0}
  .control-heading-actions{align-items:stretch}.control-heading-actions .movement-spec{text-align:left}.control-heading-actions .shell-button{justify-content:center}
  .center-zero-note{grid-area:note;margin:0 3px}
  .structure-layout{display:contents}
  .structure-canvas-wrap{grid-area:canvas;align-self:start}
  .structure-notes{grid-area:notes;grid-template-columns:repeat(4,minmax(0,1fr));margin-top:3px}
  .structure-notes div{padding:16px 18px}
  .structure-notes b{font-size:17px}
  .structure-notes span{font-size:15px}
  .conversion-grid{grid-template-columns:1fr;gap:18px}
  .conversion-card{display:block}
  .card-header{align-items:center;padding-bottom:12px}
  .conversion-workspace{grid-template-columns:minmax(210px,240px) minmax(0,1fr);align-items:start;gap:16px}
  .conversion-controls{display:grid;gap:8px}
  .conversion-visual{display:grid;gap:10px}
  .meter-stage{margin-top:0}
  .structure-canvas-wrap canvas{max-height:calc(100vh - 150px);object-fit:contain}
  .control-grid,.data-grid{grid-template-columns:1fr;margin-top:0}
  .formula-card{grid-template-columns:1fr;margin-top:0}
  .formula-card>span{grid-row:auto}
  .formula-card small{grid-column:auto}
  .full-scale-card{width:100%;margin-top:0}
}
@media(min-width:821px) and (max-width:1120px){
  .structure-notes{grid-template-columns:repeat(2,minmax(0,1fr))}
}