.period-nav{position:sticky;top:0;z-index:8;background:#fff;border-bottom:1px solid #ddd;padding:10px 0;min-width:0}.period-track{display:flex;gap:7px;overflow-x:auto;overscroll-behavior-x:contain;scrollbar-width:thin;padding:2px 1px 8px}.period-track button{flex:0 0 auto;text-align:center;min-height:54px;padding:8px 14px;font-size:14px;line-height:1.5;white-space:nowrap;border:1px solid #ddd}.period-track button small{display:block;font:11px/1.6 Georgia,serif;color:#777;margin-top:2px}.period-track button[aria-current=location]{background:#222;border-color:#222;color:#fff}.period-track button[aria-current=location] small{color:#ddd}.period-track button:disabled{color:#aaa;background:#fafafa;cursor:default}.period-track button:disabled small{color:#aaa}.term-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(215px,1fr));gap:14px}.term-tile{text-align:left;padding:22px 20px;min-height:115px;border:1px solid #ddd;display:flex;flex-direction:column;justify-content:center;gap:8px;background:#fff}.term-tile:hover{border-color:#333;background:#fafafa}.term-tile strong{font:500 19px/1.6 'Noto Serif TC',serif;overflow-wrap:anywhere}.term-tile span{font:14px/1.6 Georgia,serif;color:#777;overflow-wrap:anywhere}.era-group[data-period]{scroll-margin-top:100px}@media(max-width:600px){.period-track button{padding:7px 11px;font-size:13px}.term-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}.term-tile{padding:16px 12px;min-height:112px}.term-tile strong{font-size:16px}.term-tile span{font-size:12px}}@media(max-width:340px){.term-grid{grid-template-columns:1fr}}

.period-nav{display:flex;align-items:flex-start;gap:8px}.period-track{flex:1;min-width:0}.back-to-top{flex:0 0 30px;width:30px;height:58px;margin-top:2px;padding:0;display:flex;align-items:center;justify-content:center;background:#fff;border:1px solid #ddd;color:#333;font-size:11px}.back-to-top:hover{background:#222;color:#fff;border-color:#222}.back-to-top:focus-visible{outline:2px solid #222;outline-offset:2px}