/* 文心书院 · 老师工具箱 — shared frame for the teacher tools */
:root{--tk-paper:#f6f1e7;--tk-ink:#23303f;--tk-muted:#6b7280;--tk-teal:#0f766e;--tk-teal2:#14b8a6;--tk-amber:#f59e0b;--tk-line:#e6dccb;--tk-card:#fffdf8}
.tk-bar{position:sticky;top:0;z-index:50;display:flex;align-items:center;gap:14px;padding:8px 18px;background:rgba(255,253,248,.96);backdrop-filter:blur(6px);border-bottom:1px solid var(--tk-line);box-shadow:0 2px 10px rgba(35,48,63,.06);font-family:"PingFang SC","Microsoft YaHei","Noto Sans SC",sans-serif}
.tk-bar *{box-sizing:border-box}
.tk-brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--tk-ink);flex:none}
.tk-brand img{height:40px;width:auto;display:block}
.tk-brand b{display:block;font-size:16px;font-weight:800;line-height:1.1}
.tk-brand small{display:block;font-size:12px;font-weight:700;color:var(--tk-teal);letter-spacing:.08em}
.tk-nav{display:flex;gap:6px;flex:1;overflow-x:auto;scrollbar-width:none;padding:2px}
.tk-nav::-webkit-scrollbar{display:none}
.tk-nav a{flex:none;padding:7px 13px;border-radius:999px;font-size:14px;font-weight:700;color:var(--tk-ink);text-decoration:none;background:#fff;border:1.5px solid var(--tk-line);transition:.15s}
.tk-nav a:hover{border-color:var(--tk-teal2);color:var(--tk-teal)}
.tk-nav a.on{background:var(--tk-teal);border-color:var(--tk-teal);color:#fff}
.tk-back{flex:none;padding:7px 14px;border-radius:999px;font-size:14px;font-weight:800;color:var(--tk-teal);text-decoration:none;border:1.5px solid var(--tk-teal)}
.tk-back:hover{background:var(--tk-teal);color:#fff}
@media (max-width:760px){.tk-bar{flex-wrap:wrap;gap:8px;padding:8px 12px}.tk-brand img{height:34px}.tk-nav{order:3;flex-basis:100%}.tk-back{margin-left:auto}}
@media print{.tk-bar{display:none!important}}