/* Single CSS file */
:root{
  --bg:#f7f4ea; --text:#333; --header:#2d5aa3; --footer:#2d5aa3; --on-header:#fff;
  --card:#fff; --border:#ddd; --accent:#1a73e8; --focus:#ff9800; --radius:10px; --container:1100px; --font-scale:1;
}
@media (prefers-color-scheme: dark){
  body[data-theme="auto"]{ --bg:#000; --text:#fff; --header:#0c2a54; --footer:#0c2a54; --on-header:#fff;
    --card:#121212; --border:#303030; --accent:#82aaff; --focus:#ffb74d; }
}
body[data-theme="dark"]{ --bg:#000; --text:#fff; --header:#0c2a54; --footer:#0c2a54; --on-header:#fff;
  --card:#121212; --border:#303030; --accent:#82aaff; --focus:#ffb74d; }
body[data-theme="light"]{ --bg:#f7f4ea; --text:#333; --header:#2d5aa3; --footer:#2d5aa3; --on-header:#fff;
  --card:#fff; --border:#ddd; --accent:#1a73e8; --focus:#ff9800; }
*{box-sizing:border-box}
html{font-size:calc(16px*var(--font-scale))}
body{margin:0;font-family:system-ui,-apple-system,Segoe UI,Roboto,Nunito,Helvetica,Arial,sans-serif;background:var(--bg);color:var(--text);line-height:1.6}
a{color:var(--accent);text-decoration:underline}
a:focus,button:focus,input:focus,textarea:focus{outline:3px solid var(--focus);outline-offset:2px}
.visually-hidden{position:absolute!important;left:-9999px!important;width:1px;height:1px;overflow:hidden}
.hidden{display:none!important}
.container{max-width:var(--container);padding:1rem;margin:0 auto}
.skip-link{position:absolute;left:-9999px;top:-9999px;background:var(--accent);color:#fff;padding:.5rem 1rem;z-index:10000}
.skip-link:focus{left:0;top:0}
.site-header{background:var(--header);color:var(--on-header);position:sticky;top:0;z-index:9999;border-bottom:1px solid rgba(255,255,255,.1)}
.header-inner{display:flex;align-items:center;justify-content:space-between}
.brand{display:flex;align-items:center;gap:.5rem}
.brand-name{font-weight:800;letter-spacing:.5px}
.logo{display:block}
.header-controls{display:flex;align-items:center;gap:.5rem}
.btn{font:inherit;padding:.6rem .9rem;border-radius:8px;border:1px solid rgba(255,255,255,.3);background:transparent;color:var(--on-header);cursor:pointer}
.btn.secondary{background:transparent;border:1px solid var(--border);color:var(--text)}
.btn.icon{padding:.4rem .6rem}
.menu-overlay{position:fixed;inset:0;background:var(--header);color:var(--on-header);display:none}
.menu-overlay[aria-hidden="false"]{display:block}
.menu-header{display:flex;justify-content:flex-end}
.menu-list{list-style:none;padding:0;margin:0}
.menu-link{display:block;font-weight:800;font-size:1.5rem;padding:1rem 0;background:none;border:none;color:var(--on-header);text-align:left;cursor:pointer}
.submenu{margin-left:1rem;margin-bottom:1rem}
.submenu-list{list-style:none;padding-left:0}
.submenu-link{display:inline-block;margin-right:.5rem;padding:.4rem .7rem;border-radius:8px;border:1px solid rgba(255,255,255,.3);background:rgba(255,255,255,.08);color:var(--on-header)}
.card{background:var(--card);border:1px solid var(--border);border-radius:var(--radius);padding:1rem;margin-top:1rem}
.study-title{margin:.2rem 0 .8rem}
.chapter-list{list-style:none;padding-left:0}
.chapter-list li{margin-bottom:.5rem}
.chapter-link{display:inline-block;padding:.5rem .8rem;border-radius:8px;border:1px solid var(--border);background:var(--card);color:var(--text)}
.answer{width:100%;min-height:140px;resize:vertical;padding:.75rem;border-radius:8px;border:1px solid var(--border);background:var(--card);color:var(--text)}
.answer.notes{min-height:180px}
.study-footer{margin-top:1rem;display:flex;gap:.6rem;flex-wrap:wrap}
.chapter-picker{position:sticky;bottom:0;background:var(--bg);border-top:1px solid var(--border);padding:.8rem;display:flex;gap:.6rem;justify-content:space-between}
.btn.picker{border:1px solid var(--border);background:var(--card);color:var(--text)}
.site-footer{background:var(--footer);color:var(--on-header);margin-top:2rem;padding:.8rem 0;border-top:1px solid rgba(255,255,255,.1)}
.site-footer a{color:var(--accent)}