/* 小练习独立样式；共享页面只使用 build-entry。 */
.build-entry{background:#edf5ff;border:2px solid #b8d3ed;border-radius:16px;padding:16px;margin:14px 0;overflow-wrap:anywhere}
.build-entry h2,.build-entry h3{margin:0 0 8px}
.build-entry .build-entry-button{display:block;text-align:center;text-decoration:none;background:#185fa5;color:#fff;border-radius:12px;padding:14px 12px;min-height:48px;font-size:17px;font-weight:700;line-height:1.5}
.build-entry p{color:#405369;font-size:15px}
.build-entry .build-entry-links{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px;margin-top:12px}
.build-entry-links a{display:flex;flex-direction:column;justify-content:center;min-height:72px;background:#fff;padding:12px;border:1px solid #c1d7ec;border-radius:12px;text-decoration:none;color:#164d83;line-height:1.5}
.build-entry-links span{font-size:14px;color:#4c6177}
.build-entry a:focus-visible,.build-page :focus-visible{outline:3px solid #a04d00;outline-offset:3px}
.build-page{background:#f4f7fb;color:#243449;padding-bottom:calc(122px + env(safe-area-inset-bottom));font-size:17px;line-height:1.6;overflow-wrap:anywhere}
.build-page *, .build-page *::before, .build-page *::after{box-sizing:border-box;min-width:0}
.build-header,.build-main{max-width:760px;margin:0 auto;padding:12px 14px}
/* 页头用 flex：这里会并排出现两个链接（本站的「返回目录」+ 学科导航脚本注入的「学科首页」）。
   原来两个 a 都被 grid-column:2 钉在同一格，后插进来的那个会把「返回目录」整个盖住 —— 孩子点不到回不去。 */
.build-header{padding-bottom:0;display:flex;flex-wrap:wrap;gap:8px 10px;align-items:center}
.build-header>a{font-size:14px;flex:0 0 auto;order:2}
.build-header h1{font-size:21px;margin:0;flex:1 1 auto;order:1}
.build-picker{flex:1 1 100%;order:3;display:grid;grid-template-columns:auto minmax(0,1fr) auto;gap:8px;align-items:center}
.build-picker label{font-size:15px;font-weight:700}
.build-picker select{appearance:auto;width:100%;font:inherit;font-size:16px;border:1px solid #a9bdd1;border-radius:10px;background:#fff;color:#243449;padding:10px 8px;min-height:48px}
.build-picker>a{font-size:14px;max-width:56px;justify-self:start}
.build-device{flex:1 1 100%;order:4;font-size:14px;line-height:1.6;color:#495f77;margin:0}
.build-card{border:1px solid #d4e1ee;border-radius:18px;padding:18px;background:#fff;box-shadow:0 3px 16px #2e5d8710}
.build-card h2{font-size:23px;line-height:1.45;margin:8px 0 12px}
.build-card h3{font-size:19px;line-height:1.5;margin:8px 0 12px}
.build-eyebrow,.build-count,.build-record{font-size:14px;line-height:1.55;color:#4b637c}
.build-eyebrow{font-weight:700;color:#185fa5;margin:0}
.build-count{background:#f1f6fc;border-radius:10px;padding:10px 12px;margin:12px 0}
.build-count strong{color:#185fa5;font-size:17px}
.build-count span{display:block;margin-top:4px}
.build-record{margin:0 0 10px}
.build-record:empty{display:none}
.build-goal{font-size:18px;line-height:1.8;margin:10px 0 16px}
.build-setup{border:1px solid #d4e1ee;background:#fafcff;border-radius:12px;margin:12px 0;padding:0 12px}
.build-setup summary{cursor:pointer;font-weight:700;padding:12px 0;min-height:48px}
.build-question{margin-top:16px}
.build-question label{display:block;font-weight:700;margin-bottom:10px}
.build-question label span{display:block;font-weight:400;margin-top:4px}
.build-input{display:block;width:100%;max-width:100%;min-height:48px;border:1px solid #9bb1c7;border-radius:11px;padding:12px;font:inherit;font-size:17px;background:#fff;color:#243449}
.build-page .btn{min-height:48px;white-space:normal;line-height:1.4;padding:12px;font-size:17px}
.build-page button:disabled{opacity:.55;cursor:not-allowed}
.build-primary{display:block;width:100%;margin-top:18px}
.build-hint{font-size:14px;color:#4b637c;line-height:1.6;margin:8px 0}
.build-text-button{appearance:none;display:inline-block;background:transparent;border:0;border-radius:8px;padding:12px 4px;min-height:48px;font:inherit;font-size:15px;color:#315f8c;text-decoration:underline;text-underline-offset:4px;cursor:pointer;text-align:left}
.build-answer-toggle{display:block;margin:14px auto 0;color:#50647b;text-align:center}
.build-step-nav{display:flex;gap:10px;margin-top:18px}
.build-step-nav button{flex:1}
.build-step-header{display:flex;align-items:center;justify-content:space-between;gap:10px}
.build-step-header p{margin:0;color:#4b637c;font-size:15px}
.build-image{max-width:100%;overflow-x:hidden;touch-action:pan-y;overscroll-behavior-x:contain;border:1px solid #d4e1ee;border-radius:12px;background:#fffcf6;margin:12px 0}
.build-image-controls{display:flex;flex-wrap:wrap;gap:10px;margin:4px 0 12px}
.build-image-controls button{flex:1;text-align:center;border:1px dashed #b9cde0;text-decoration:none}
.build-image-controls button[hidden]{display:none}
.build-image .kbfig{margin:0;border:0;box-shadow:none;background:transparent;padding:12px;display:block}
.build-image svg.kb-svg{display:block;max-width:none!important;height:auto;margin:0}
.build-image figcaption{font-size:15px;text-align:left;margin-top:12px;line-height:1.6;color:#415970}
.build-image-hint{font-size:13px;color:#4b637c;margin:6px 0}
.build-answer{border-top:2px solid #d4e1ee;margin-top:20px;padding-top:16px}
.build-answer ol,.build-answer ul{padding-left:24px}
.build-checks{border:0;padding:0;margin:18px 0}
.build-checks legend{font-size:19px;font-weight:700;margin-bottom:10px}
.build-check{display:flex;align-items:flex-start;gap:10px;border:1px solid #d4e1ee;border-radius:12px;padding:12px;margin:8px 0;cursor:pointer;min-height:48px;line-height:1.6}
.build-check input{width:22px;height:22px;flex:0 0 22px;margin:3px 0 0;accent-color:#185fa5}
.build-feedback{background:#eef5fc;color:#2b4c6d;border:1px solid #c5daef;border-radius:12px;padding:12px;margin-top:12px}
.build-feedback:empty{display:none}
.build-notice{max-width:732px;margin:12px auto;background:#fff5e5;border:1px solid #e4c78d;color:#6e501d;border-radius:12px;padding:12px;font-size:15px}
.build-footer .bb-in{max-width:732px}
/* 底部是「换题」的主操作（下一题 / 下一课 / 回目录）。原来这里把主按钮降权成白底虚线，
   但在这个位置虚线会被当成"禁用"—— 孩子翻到最后一题时，两组按钮全灰，不知道点哪。 */
.build-footer .btn.primary{box-shadow:0 2px 10px #185fa51f;white-space:nowrap}
.build-footer .btn.ghost{white-space:nowrap}
@keyframes buildNextPulse{0%,100%{box-shadow:0 2px 10px #185fa51f}50%{box-shadow:0 0 0 6px #185fa52e}}
.build-next-hint{animation:buildNextPulse 1.1s ease-in-out 3}
@media (prefers-reduced-motion:reduce){
  .build-next-hint{animation:none;outline:3px solid #185fa5;outline-offset:2px}
}
.build-count summary{cursor:pointer}
.build-count[open] span{margin-top:8px}
.build-task-count{max-width:732px;margin:0 auto 8px;text-align:center;font-size:14px;color:#4b637c}
@media(max-width:390px){
  .build-header,.build-main{padding-left:10px;padding-right:10px}
  .build-card{padding:14px}
  .build-card h2{font-size:21px}
  .build-goal{font-size:17px}
  .build-entry{padding:12px}
  .build-entry .build-entry-links{gap:8px}
}
@media print{.build-footer,.build-picker,.build-text-button,.build-page button{display:none}.build-page{padding-bottom:0}.build-image{overflow:visible}}