/* Modo oscuro (sólo páginas de la app) + tamaño de letra + botón flotante de ajustes */
html{font-size:calc(100% * var(--user-zoom,1))}
html[data-theme="dark"] body.study-page,
html[data-theme="dark"] body.test-page,
html[data-theme="dark"] body.app-page{
  --bg:#0d1a1d; --surface:#142a2f; --surface-2:#18343a; --line:#244249; --line-soft:#1d363c;
  --text:#d5e6e9; --muted:#93b0b5; --brand-ink:#e8f4f6; --ink-2:#cfe4e8;
  --brand-deep:#6cc3cf; --accent-soft:#3a2420; --amber-soft:#3a3020; --green-soft:#17352a;
  --shadow:0 10px 30px -12px rgba(0,0,0,.6); --shadow-lift:0 24px 50px -18px rgba(0,0,0,.7);
  color-scheme:dark;
}
html[data-theme="dark"] body.study-page .study-topbar,
html[data-theme="dark"] body.test-page .test-topbar{background:var(--surface);border-color:var(--line)}
html[data-theme="dark"] body.study-page .btn-primary,
html[data-theme="dark"] body.test-page .btn-primary,
html[data-theme="dark"] body.app-page .btn-primary{color:#fff}
html[data-theme="dark"] body.study-page .sec-link[data-lvl="6"]{color:#8fb0b6}
html[data-theme="dark"] .pdf-frame,html[data-theme="dark"] .page-img{filter:invert(.92) hue-rotate(180deg)}

.rtc-fab{position:fixed;left:14px;bottom:14px;z-index:60;display:flex;gap:4px;padding:4px;border-radius:999px;
  background:var(--surface,#fff);border:1px solid var(--line,#d7e7e9);box-shadow:0 8px 22px -8px rgba(12,34,38,.35)}
.rtc-fab button{border:0;background:transparent;color:var(--text,#1e3c42);font:700 .85rem var(--font-body,system-ui);
  min-width:34px;height:34px;border-radius:999px;cursor:pointer}
.rtc-fab button:hover{background:var(--surface-2,#eefafb)}
@media print{.rtc-fab{display:none}}