[hidden]{display:none!important}
.energy-calculator{max-width:460px;padding:16px;border:1px solid var(--line);border-radius:12px;background:var(--paper);margin:16px 0}
.energy-calculator #tool-expression{max-width:none;font-size:1.1rem;background:var(--panel-bg)}
.energy-calc-keys{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:8px}
.energy-calc-keys button{min-height:48px;margin:0;font-size:1.2rem;padding:8px}
.energy-calc-data{display:flex;flex-wrap:wrap;gap:6px;margin:12px 0}
.energy-calc-data button{font-size:.85rem;overflow-wrap:anywhere;max-width:100%}
.energy-calculator #tool-result{font-size:1.3rem;font-weight:700;background:var(--panel-bg)}
.energy-calculator #calculator-preview{min-height:48px;background:var(--panel-bg)}
.energy-trace-steps{border-left:3px solid var(--primary-color);padding-left:14px;margin-bottom:18px}
.energy-trace-steps p{font-weight:600}.energy-trace-steps button{min-height:44px}
.energy-fine-controls{display:flex;align-items:center;flex-wrap:wrap;gap:8px;margin-top:10px}
.energy-fine-controls button{min-height:44px;min-width:90px}
.energy-intersection-gap{padding:12px;background:var(--paper);border-radius:8px}
/* Keep the task visible; context and experiments can be opened on demand. */
#exercise-statement>summary,#illustration-panel>summary{cursor:pointer;font-weight:700;font-size:1.05rem;padding:5px 0}
#question-context{scroll-margin-top:16px;margin-bottom:12px}
#question-context:focus-visible{outline:3px solid var(--primary-color);outline-offset:3px}
.practice-stage{font-size:.85rem;color:var(--muted);margin-top:0!important}
#question-context h2{margin-top:6px}
#illustration-panel{margin-bottom:12px}
.practice-answer-instruction{font-weight:600;margin-top:0!important}
#question-nav button{min-width:40px;min-height:40px}
.energy-practice-layout{display:grid;grid-template-columns:220px minmax(0,1fr) 330px;gap:18px;align-items:start}
.practice-main,.practice-tools{min-width:0}.practice-tools{position:sticky;top:14px;max-height:calc(100vh - 28px);overflow:auto;padding:16px}
#cases{display:grid;gap:10px}#cases button{text-align:left}#cases [aria-current=true]{border:2px solid var(--primary-color);background:var(--paper)}
.practice-main p,.practice-tools p{margin:10px 0}.practice-main .card{padding:20px}#question-nav{display:flex;flex-wrap:wrap;gap:7px;margin:15px 0}#question-nav [aria-current=true]{border:2px solid var(--primary-color)}
.practice-options{display:grid;gap:10px}.practice-options button{display:flex;gap:12px;align-items:center;text-align:left;padding:14px;min-width:0;overflow:hidden}.practice-options math{font-size:1.1rem}.practice-option-letter{background:var(--paper);border-radius:50%;padding:4px 9px;flex-shrink:0}
.practice-options button>span:last-child{min-width:0;overflow-x:auto;padding:3px}
math{font-family:'Cambria Math',serif;font-size:1.1em;max-width:100%}.practice-formula{overflow-x:auto;padding:12px;background:var(--paper);border-radius:9px;margin:12px 0}
.practice-input-row{display:flex;flex-wrap:wrap;gap:10px;align-items:end}.practice-input-row label{margin:0}.practice-input-row input{width:160px;max-width:100%}.practice-input-row select{min-width:100px}.practice-actions{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px}.practice-feedback{min-height:0;padding:12px;border-radius:9px}.practice-feedback:empty{display:none}.practice-feedback.ok{background:#e8f5e9;color:#175331}.practice-feedback.bad{background:#ffebee;color:#8e2525}
.practice-tools details{border-top:1px solid var(--line);padding:13px 0}.practice-tools summary{cursor:pointer;font-weight:700}.practice-tools input:not([type=range]),.practice-tools textarea,.practice-tools select{width:100%;margin-top:5px;padding:8px}.practice-tools input[type=range]{width:100%}.practice-tools label{font-size:.9rem;margin:10px 0}.practice-tools button{margin:4px 0}.practice-tools output{display:block;overflow-wrap:anywhere;margin:10px 0;font-variant-numeric:tabular-nums}.practice-tools small{display:block;line-height:1.5}.practice-param-grid{display:grid;grid-template-columns:1fr 1fr;gap:8px}.practice-param-grid input{min-width:0}.practice-plot{margin:12px 0}.practice-plot svg{width:100%;height:auto}.practice-plot text{font-family:'Segoe UI',sans-serif;font-size:13px}.practice-plot-readout{font-size:.9rem;min-height:2em}.practice-tool-error{color:#9b2525}
.practice-tools input[type=checkbox]{width:auto!important}.practice-tools select{max-width:100%}
.practice-tool-context{padding:10px;border-radius:9px;background:var(--paper);font-size:.9rem;line-height:1.5}.practice-tool-context span{display:block;color:var(--muted);margin-top:5px}#tool-restore-preset{font-size:.85rem;text-align:left}
.practice-recall{margin:16px 0;padding:14px;border:1px solid var(--line);border-radius:10px;background:var(--paper)}.practice-recall h3{font-size:1rem;margin:0 0 10px}.practice-recall-formula{display:flex;flex-wrap:wrap;gap:8px;align-items:center;margin:10px 0;min-width:0;overflow-x:auto}
#energy-plot-modal{width:min(900px,94vw);max-height:94vh;overflow:auto;border:1px solid var(--line);border-radius:14px;padding:18px;background:var(--panel-bg);color:var(--text-color)}#energy-plot-modal::backdrop{background:rgb(16 36 62 / 45%)}#energy-plot-modal input[type=range]{width:100%}#energy-plot-modal .practice-plot svg{max-height:65vh}
.practice-diagram{margin:12px auto;max-width:600px}.practice-diagram svg{max-height:220px}.practice-diagram text{font-family:'Segoe UI',sans-serif;font-size:17px;fill:#172536}.practice-note{color:var(--muted)}.practice-badges{display:flex;flex-wrap:wrap;gap:8px}.practice-badges span{padding:5px 10px;border:1px solid var(--line);border-radius:18px}.practice-solution{padding-top:10px}.practice-solution li{margin:8px 0}
@media(max-width:1150px){.energy-practice-layout{grid-template-columns:210px minmax(0,1fr)}.practice-tools{grid-column:2;position:static;max-height:none}}
@media(max-width:760px){.energy-practice-layout{grid-template-columns:1fr}.mob-navigation{position:static}.practice-tools{grid-column:1}.practice-main .card{padding:16px}.practice-options math{font-size:1rem}.practice-param-grid{grid-template-columns:1fr 1fr}.practice-tools{order:3}}
@media print{.mob-navigation,.practice-tools,#question-nav,.practice-actions{display:none}.energy-practice-layout{display:block}}
/* Question-specific illustrations occupy the working area, rather than a narrow tool column. */
.energy-practice-layout{grid-template-columns:220px minmax(0,1fr)}
.practice-tools{position:static;max-height:none;overflow:visible;padding:18px}
.energy-illustration-heading h3{margin-top:0;font-size:1.2rem}.energy-illustration-heading p{color:var(--muted)}
.energy-illustration-control{padding:12px 16px;background:var(--paper);border-radius:10px;margin:15px 0}.energy-illustration-control label{margin:0}.energy-illustration-control label>span,.energy-comparison-settings label>span{float:right;font-variant-numeric:tabular-nums}.energy-illustration-control .moves{margin-top:8px}
.energy-comparison-settings{margin:10px 0}.energy-comparison-settings input[type=range]{margin-top:10px}
.energy-visual-grid{display:grid;grid-template-columns:minmax(0,.8fr) minmax(0,1.2fr);gap:16px;align-items:center}.energy-visual-grid>div{min-width:0}.energy-visual-grid svg{width:100%;height:auto}.energy-visual-grid text{font-family:var(--font-family);font-size:17px;fill:var(--text-color)}.energy-visual-plot text{font-size:18px}
.energy-legend{display:flex;flex-wrap:wrap;gap:10px;margin-top:8px;font-size:.88rem}.energy-legend span{display:flex;align-items:center;gap:6px}.energy-legend i{width:18px;height:4px;display:inline-block;flex-shrink:0}
.energy-bar-list{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:14px;margin:15px 0}.energy-bar-list>div>span{display:flex;justify-content:space-between;gap:10px;font-size:.9rem}.energy-bar-track{height:12px;border:1px solid var(--line);background:var(--paper);border-radius:5px;overflow:hidden;margin-top:5px}.energy-bar-track i{display:block;height:100%}
.energy-comparison{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:16px 0}.energy-comparison>span{padding:12px;background:var(--paper);border-radius:9px;font-size:.9rem}.energy-comparison strong{display:block;font-size:1.2rem;margin-top:6px}.energy-visual-note{font-size:.85rem;color:var(--muted)}
.energy-simple-calculation{margin-top:18px}.energy-simple-calculation input,.energy-simple-calculation select{max-width:420px;display:block}.energy-simple-calculation output{padding:10px;background:var(--paper);border-radius:8px;min-height:40px}
@media(max-width:1000px){.energy-visual-grid{grid-template-columns:1fr}.energy-visual-scheme svg{max-height:210px}.energy-visual-plot svg{max-height:340px}}
@media(max-width:760px){.energy-practice-layout{grid-template-columns:1fr}.practice-tools{padding:14px}.energy-comparison{grid-template-columns:1fr}.energy-comparison>span{display:flex;justify-content:space-between;gap:12px;align-items:center}.energy-comparison strong{margin-top:0}.energy-visual-plot text{font-size:21px}.energy-visual-grid text{font-size:19px}}