/* 「Visual Learning」下拉菜单（2026-10-31）：链接多了（约 22 个）—— 桌面两栏、限高可滚动、按钮不折行；
   同时带上基础规则，页面没引 ime.css 时菜单也不会散开 */
.nav-dd{position:relative;display:inline-block}
.nav-dd-btn{font:inherit;color:inherit;background:none;border:0;cursor:pointer;padding:0;display:inline-flex;align-items:center;gap:4px;white-space:nowrap}
.nav-dd-btn.active,.nav-dd.open .nav-dd-btn{color:#1b6f8a}
.nav-dd-caret{font-style:normal;font-size:11px;opacity:.7}
.nav-dd-menu{display:none;position:absolute;top:calc(100% + 10px);left:50%;transform:translateX(-50%);background:#fff;border:1px solid #e3e8e6;border-radius:12px;box-shadow:0 12px 32px rgba(19,52,63,.12);padding:8px 10px;z-index:60;text-align:left;
  width:max-content;max-width:min(560px,calc(100vw - 32px));max-height:calc(100vh - 96px);overflow-y:auto;column-count:2;column-gap:12px}
.nav-dd.open .nav-dd-menu{display:block}
.nav-dd-menu a{display:block;padding:6px 12px;border-radius:8px;white-space:nowrap;font-size:14px;break-inside:avoid;line-height:1.35}
.nav-dd-menu a:hover,.nav-dd-menu a.active{background:#eef6f3;color:#1b6f8a}
.nav-dd-group{font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:#8a8f93;padding:8px 12px 2px;break-after:avoid;break-inside:avoid}
.nav-dd-soon{color:#b5bcc0;text-transform:none;letter-spacing:0;padding-top:10px;border-top:1px dashed #eef3f1;margin-top:6px;column-span:all}
@media (max-width:900px){.nav-dd{display:block}.nav-dd-menu{position:static;transform:none;display:block;box-shadow:none;border:0;padding:0 0 0 12px;min-width:0;width:auto;max-height:none;overflow:visible;column-count:1}.nav-dd-btn{pointer-events:none}}