/* One persistent navigation frame for every full-screen learning section. */
.app-header{position:relative;flex:none;min-height:68px;padding:10px 24px;gap:12px;z-index:25}
.app-header .app-navigation-button,.app-header .app-course-button{display:inline-flex;align-items:center;justify-content:center;flex:none;min-height:44px;height:auto;width:auto;gap:7px;margin:0;padding:8px 13px;border:1px solid var(--line);border-radius:8px;font-size:13px;font-weight:700;line-height:1.35;white-space:nowrap;background:#fff;color:var(--blue-dark)}
.app-header .app-navigation-button:hover,.app-header .app-course-button:hover{background:var(--sky-soft)}
.app-header .app-navigation-button .app-back-arrow{font-size:21px;line-height:1}
.app-header .app-course-button{margin-left:auto;background:var(--sky-faint)}
.app-header .teacher-identity{margin-right:0;min-width:0;gap:9px}
.app-header .teacher-identity>div{min-width:0}
.app-header #app-subtitle{max-width:360px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.app-navigation{flex:none;min-width:0;max-width:100%;background:#f6fbff;border-bottom:1px solid var(--line);overflow-x:auto;overflow-y:hidden;overscroll-behavior-x:contain;scrollbar-width:thin;scrollbar-color:#c1d8ee transparent;padding:0 24px}
.app-navigation ol{display:flex;align-items:center;gap:0;min-width:max-content;list-style:none;margin:0;padding:0}
.app-navigation li{display:flex;align-items:center;flex:none;min-width:0}
.app-navigation li+li::before{content:'›';flex:none;color:#83a0bc;margin:0 9px;font-size:18px}
.app-navigation button,.app-breadcrumb-current{display:inline-flex;align-items:center;min-height:40px;padding:5px 1px;font-size:12px;line-height:1.4;white-space:nowrap}
.app-navigation button{border:0;border-radius:4px;background:transparent;color:#315f8f;text-align:left;font-weight:600}
.app-navigation button:hover{color:var(--blue-dark);text-decoration:underline;text-underline-offset:3px}
.app-breadcrumb-current{color:#526a80;font-weight:500}
.app-navigation button:focus-visible{outline-offset:-2px}
.app-progress{position:relative;top:auto;flex:none}
@media(max-width:680px){
 .app-header{min-height:56px;padding:7px 10px;gap:6px}
 .app-header .app-navigation-button,.app-header .app-course-button{min-height:40px;padding:7px 9px;gap:5px;font-size:12px}
 .app-header .teacher-identity{gap:6px}
 .app-header .teacher-identity img{width:32px;height:32px;flex:none}
 .app-header .teacher-identity strong{font-size:12px;white-space:nowrap}
 .app-header #app-subtitle{display:none}
 .app-header .ai-badge{font-size:8px;padding:1px 3px;margin-left:1px}
 .app-navigation{padding-inline:12px}
 .app-navigation button,.app-breadcrumb-current{font-size:11px}
 .app-navigation li+li::before{margin-inline:7px}
}
@media(max-width:430px){
 .app-header .teacher-identity>div{display:none}
 .app-header .teacher-identity{margin-left:0}
}
.keyboard-open .app-header{min-height:50px;padding-block:5px}
.keyboard-open .app-navigation{display:none}
@media(prefers-reduced-motion:reduce){.app-navigation{scroll-behavior:auto}}