:root{--text:#172033;--muted:#647084;--line:#dce4ee;--accent:#2563eb;--accent2:#0f766e;--soft:#eef6ff;--warn:#fff7ed;--shadow:0 10px 28px rgba(15,23,42,.08);--max:1520px}*,*::before,*::after{box-sizing:border-box}html{width:100%;max-width:100%;overflow-x:hidden;overflow-x:clip;scroll-behavior:smooth;-webkit-text-size-adjust:100%;text-size-adjust:100%}body{margin:0;width:100%;max-width:100%;min-width:0;overflow-x:hidden;overflow-x:clip;background:linear-gradient(180deg,#f8fbff,#f7f8fb 45%,#fff);color:var(--text);font-family:Inter,system-ui,-apple-system,"Segoe UI",sans-serif;line-height:1.67}main,section,article,aside,header,footer,nav,div,form,ul,ol,li,.wrap,.lay,.card,.content,.side{min-width:0;max-width:100%}img,svg,video,canvas,iframe,embed,object{display:block;max-width:100%;height:auto}h1,h2,h3,h4,h5,h6,p,a,span,strong,b,em,small,li,button,label,input,select,textarea,td,th{overflow-wrap:anywhere;word-break:normal}a{color:#1d4ed8;text-decoration:none}a:hover{text-decoration:underline}button,input,select,textarea{font:inherit}pre,code{direction:ltr!important;text-align:left!important;unicode-bidi:isolate}pre{max-width:100%;overflow-x:auto;-webkit-overflow-scrolling:touch;white-space:pre}#readingProgress{position:fixed;inset-block-start:0;inset-inline-start:0;width:0;height:4px;background:var(--accent);z-index:9999}.wrap{width:min(calc(100% - 20px),var(--max));margin-inline:auto;padding-block:10px 40px}.topbar,.site-header,.translate-row{background:#fff;border:1px solid var(--line);border-radius:1rem}.topbar{display:flex;align-items:center;justify-content:space-between;gap:.75rem;flex-wrap:wrap;padding:.5rem .75rem}.topbar p{margin:0}.top-pill{font-weight:800}.site-header{display:flex;align-items:center;justify-content:space-between;gap:1rem;margin-block-start:.6rem;padding:.65rem .9rem;box-shadow:var(--shadow)}.site-logo img{max-height:58px;width:auto}.main-nav ul{display:flex;gap:.4rem;flex-wrap:wrap;list-style:none;padding:0;margin:0}.main-nav a{display:block;padding:.5rem .65rem;border-radius:.6rem;font-weight:700}.main-nav a:hover{background:var(--soft)}.site-menu-button{display:none;border:1px solid var(--line);background:#fff;border-radius:.6rem;padding:.5rem .7rem}.site-overlay{position:fixed;inset:0;background:rgba(15,23,42,.45);z-index:89;display:none}.site-drawer{position:fixed;inset-block:0;inset-inline-start:0;width:min(330px,88vw);height:100dvh;background:#fff;z-index:90;padding:1rem;transform:translateX(-105%);transition:transform .2s;overflow:auto}.site-drawer.open{transform:none!important}.site-drawer ul{list-style:none;padding:0}.site-drawer a{display:block;padding:.6rem}.translate-row{display:flex;align-items:center;gap:.6rem;flex-wrap:wrap;margin-block:.75rem;padding:.65rem .75rem}.translate-help{color:var(--muted);font-size:.92rem}#google_translate_element,.goog-te-gadget,.goog-te-gadget-simple,.goog-te-combo{max-width:100%!important;min-width:0!important}.goog-te-gadget{white-space:normal!important}.goog-te-combo{width:auto!important}.goog-te-gadget span,.goog-te-gadget a{white-space:normal!important;overflow-wrap:anywhere}.hero{background:linear-gradient(135deg,#eef6ff,#ecfdf5);border:1px solid #d7e5f5;border-radius:1rem;padding:1.4rem;margin-block-end:1rem}.hero h1{font-size:clamp(2rem,4vw,3.4rem);line-height:1.08;margin:.2em 0}.sub{font-weight:800;color:#0f766e}.meta,.tools,.tool-actions,.jumps,.chapter-nav{display:flex;gap:.5rem;flex-wrap:wrap;min-width:0;max-width:100%}.pill{background:#fff;border:1px solid #dbe4ee;border-radius:999px;padding:.4rem .65rem;font-weight:700}.tools{justify-content:space-between;align-items:center;margin-block:.75rem}.tool-btn{border:1px solid var(--line);background:#fff;border-radius:.6rem;padding:.5rem .7rem;font-weight:700;cursor:pointer}.course-menu-btn{display:none;width:100%;align-items:center;justify-content:center;gap:.5rem;border:1px solid #bfdbfe;background:#eff6ff;border-radius:.75rem;padding:.7rem .9rem;font-weight:800;color:#1d4ed8;margin:.75rem 0}.course-overlay{position:fixed;inset:0;background:rgba(15,23,42,.45);z-index:94;display:none}.lay{display:grid;grid-template-columns:minmax(260px,330px) minmax(0,1fr);gap:1rem;align-items:start;width:100%}.card{background:#fff;border:1px solid var(--line);border-radius:1rem;box-shadow:var(--shadow)}.side{position:sticky;inset-block-start:.6rem;max-height:calc(100dvh - 20px);overflow:auto}.side-head{display:flex;align-items:center;justify-content:space-between;padding:.9rem 1rem;border-block-end:1px solid var(--line)}.course-close{display:none}.side-body{padding:1rem}.chapter-search{display:grid;gap:.4rem}.chapter-search input{width:100%;min-width:0;padding:.55rem .65rem;border:1px solid var(--line);border-radius:.6rem}.course-list{list-style:none;padding:0;margin:.75rem 0;display:grid;gap:.35rem}.chapter-group>a{display:grid;grid-template-columns:minmax(44px,54px) minmax(0,1fr);gap:.45rem;padding:.55rem;border-radius:.65rem}.chapter-group>a.active,.chapter-group>a:hover{background:var(--soft)}.num{font-weight:900;color:#1d4ed8}.txt b,.txt em{display:block}.txt em{font-style:normal;color:var(--muted);font-size:.88rem}.subchapter-list{display:none;list-style:none;padding:.25rem 0 .35rem 1rem;margin:0}.chapter-group.open>.subchapter-list{display:block}.subchapter-list a{display:block;padding:.28rem .45rem;border-radius:.45rem;font-size:.9rem}.subchapter-list a:hover{background:#f6f9ff}.content{min-width:0}.content-body{padding:1rem}.topic-nav{background:#fbfdff;border:1px solid var(--line);border-radius:.85rem;padding:.85rem;margin-block-end:1rem}.jumps a{background:#edf4ff;padding:.45rem .65rem;border-radius:999px;font-weight:700;white-space:normal}.topic{border:1px solid var(--line);border-radius:1rem;padding:1.1rem;margin:1rem 0;background:#fff;min-width:0}.topic h2{font-size:clamp(1.4rem,3vw,2rem);scroll-margin-top:16px}.panel,.practice,.mistake{border:1px solid var(--line);border-radius:.8rem;padding:.9rem;margin:.9rem 0;background:#fbfdff}.panel.note{border-inline-start:5px solid #2563eb}.panel.examples{border-inline-start:5px solid #0f766e}.practice{border-inline-start:5px solid #d97706;background:#fffaf0}.mistake{border-inline-start:5px solid #dc2626;background:#fff7f7}.code-panel{position:relative;background:#0b1220;color:#e5e7eb}.code-panel h3{color:#fff}.code-panel pre{background:#050b15;color:#dbeafe;border-radius:.65rem;padding:.9rem}.copy-code{position:absolute;inset-block-start:.6rem;inset-inline-end:.6rem;border:1px solid #64748b;background:#111827;color:#fff;border-radius:.5rem;padding:.35rem .55rem}.examples-list{padding-inline-start:1.4rem}.examples-list li{margin:.65rem 0}.qa details{border-block-start:1px solid var(--line);padding:.65rem 0}.qa summary{cursor:pointer;font-weight:800}.expected{background:#eefbf4;border-radius:.65rem;padding:.65rem}.chapter-nav{justify-content:space-between;margin-block:1.4rem}.chapter-nav a{padding:.55rem .75rem;border:1px solid var(--line);border-radius:.6rem;background:#fff;font-weight:700}.footer{margin-block-start:1.5rem;padding:1.25rem;background:#111827;color:#e5e7eb;border-radius:1rem}.footer-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:1rem}.footer a{color:#bfdbfe}[dir="rtl"] body,.rtl-language{direction:rtl;text-align:right}[dir="rtl"] pre,[dir="rtl"] code,.rtl-language pre,.rtl-language code{direction:ltr!important;text-align:left!important;unicode-bidi:isolate}[dir="rtl"] .site-drawer,.rtl-language .site-drawer{transform:translateX(105%)}@media(max-width:1050px){.lay{grid-template-columns:minmax(0,1fr)}.main-nav{display:none}.site-menu-button{display:block}.course-menu-btn{display:flex;position:sticky;top:6px;z-index:92}.side{position:fixed;inset-block:0;inset-inline-start:0;z-index:95;width:min(390px,92vw);height:100dvh;max-height:none;transform:translateX(-105%);transition:transform .2s;background:#fff}.side.open{transform:none!important}.course-close{display:inline-block}[dir="rtl"] .side,.rtl-language .side{transform:translateX(105%)}}@media(max-width:700px){.wrap{width:calc(100% - 10px)}.content-body,.topic{padding:.75rem}.hero{padding:1rem}.translate-row{align-items:flex-start;flex-direction:column}.translate-row>*{max-width:100%!important;min-width:0!important}.tools,.tool-actions{width:100%}.tool-btn{flex:1 1 auto}.footer-grid{grid-template-columns:1fr}.chapter-nav a{flex:1 1 100%;text-align:center}}@media(max-width:420px){.wrap{width:calc(100% - 6px)}.content-body,.topic{padding:.6rem}.chapter-group>a{grid-template-columns:minmax(40px,48px) minmax(0,1fr)}}@media print{.side,.course-menu-btn,.course-overlay,.site-drawer,.site-overlay,.site-menu-button,.translate-row,.tools,#readingProgress{display:none!important}.lay{display:block}.wrap{width:100%}.card,.topic{box-shadow:none;border-color:#bbb}}

/* ===== 2026-09-23 mobile chapter / translate / social repair ===== */
.translate-row{
  min-height:36px!important;
  margin-block:.45rem!important;
  padding:.3rem .5rem!important;
  gap:.4rem!important;
  flex-direction:row!important;
  align-items:center!important;
  line-height:1.1!important;
  font-size:.82rem!important;
}
.translate-row>span:first-child{font-weight:800;white-space:nowrap}
.translate-help{display:none!important}
#google_translate_element{min-height:28px!important;display:flex!important;align-items:center!important;max-width:100%!important}
.goog-te-gadget{font-size:11px!important;line-height:1!important;margin:0!important}
.goog-te-gadget-simple{
  min-height:28px!important;height:28px!important;
  padding:1px 5px!important;margin:0!important;
  display:inline-flex!important;align-items:center!important;
  border-radius:7px!important;max-width:100%!important
}
.goog-te-combo{
  height:28px!important;min-height:28px!important;
  padding:1px 5px!important;margin:0!important;
  font-size:12px!important;line-height:1!important;
  border-radius:6px!important;max-width:100%!important
}
.footer-social{
  display:flex;justify-content:center;align-items:center;
  gap:8px;flex-wrap:wrap;margin:14px 0 8px
}
.footer-social a{
  width:34px!important;height:34px!important;min-width:34px!important;min-height:34px!important;
  max-width:34px!important;max-height:34px!important;padding:0!important;
  display:inline-flex!important;align-items:center!important;justify-content:center!important;
  border-radius:50%;background:#fff;text-decoration:none;
  box-shadow:0 4px 12px rgba(0,0,0,.18)
}
.footer-social svg{width:17px!important;height:17px!important;max-width:17px!important;max-height:17px!important;display:block;fill:currentColor}
.footer-social a:nth-child(1){color:#1877f2}.footer-social a:nth-child(2){color:#e4405f}.footer-social a:nth-child(3){color:#111}.footer-social a:nth-child(4){color:#ff0000}.footer-social a:nth-child(5){color:#111}.footer-social a:nth-child(6){color:#0088cc}
.index-course-side{display:none}
@media(max-width:1050px){
  .course-menu-btn{
    display:flex!important;visibility:visible!important;opacity:1!important;
    position:sticky!important;top:4px!important;z-index:993!important;
    min-height:42px!important;margin:.45rem 0!important;padding:.55rem .75rem!important
  }
  .side.open{
    display:block!important;visibility:visible!important;opacity:1!important;
    transform:none!important;z-index:995!important
  }
  .index-course-side{display:block}
  .course-overlay{z-index:994!important}
}
@media(max-width:700px){
  .translate-row{
    display:flex!important;visibility:visible!important;opacity:1!important;
    min-height:34px!important;padding:.25rem .4rem!important;margin-block:.35rem!important;
    flex-direction:row!important;align-items:center!important;flex-wrap:wrap!important
  }
  .translate-row>span:first-child{font-size:.76rem}
  .goog-te-gadget-simple,.goog-te-combo{height:27px!important;min-height:27px!important}
}
@media(max-width:420px){
  .course-menu-btn{
    display:flex!important;visibility:visible!important;opacity:1!important;
    width:100%!important;min-height:40px!important
  }
  .translate-row{
    display:flex!important;visibility:visible!important;opacity:1!important;
    min-height:32px!important;margin-block:.25rem!important;padding:.2rem .35rem!important;gap:.3rem!important
  }
  .translate-row>span:first-child{font-size:.72rem}
  .footer-social{gap:7px}
  .footer-social a{width:32px!important;height:32px!important;min-width:32px!important;min-height:32px!important}
  .footer-social svg{width:16px!important;height:16px!important}
}



/* ===== UIUX visible mobile top menu + translator ===== */

/* Base: keep both visible */
.site-header,.main-nav,.translate-row,#google_translate_element{
  visibility:visible!important;
  opacity:1!important;
}
.site-header{
  width:100%!important;
  max-width:100%!important;
  min-width:0!important;
}
.site-logo img{
  display:block!important;
  width:150px!important;
  max-width:150px!important;
  height:auto!important;
  object-fit:contain!important;
}
.main-nav{
  display:block!important;
  min-width:0!important;
}
.main-nav ul{
  display:flex!important;
  align-items:center!important;
  justify-content:flex-end!important;
  flex-wrap:wrap!important;
  gap:5px!important;
  margin:0!important;
  padding:0!important;
  list-style:none!important;
}
.main-nav a{
  display:block!important;
  white-space:nowrap!important;
}

/* Google Translate: always visible and compact */
.translate-row{
  display:flex!important;
  visibility:visible!important;
  opacity:1!important;
  align-items:center!important;
  flex-wrap:wrap!important;
  gap:5px!important;
  min-height:33px!important;
  padding:3px 6px!important;
  margin:4px 0 7px!important;
  font-size:.78rem!important;
  line-height:1.1!important;
}
.translate-help{display:none!important}
#google_translate_element{
  display:flex!important;
  visibility:visible!important;
  opacity:1!important;
  align-items:center!important;
  min-height:27px!important;
  max-width:100%!important;
}
.goog-te-gadget{
  font-size:11px!important;
  line-height:1!important;
  margin:0!important;
}
.goog-te-gadget-simple{
  display:inline-flex!important;
  align-items:center!important;
  min-height:27px!important;
  height:27px!important;
  max-width:100%!important;
  padding:1px 5px!important;
  margin:0!important;
  border-radius:7px!important;
}
.goog-te-combo{
  display:inline-block!important;
  visibility:visible!important;
  opacity:1!important;
  min-height:27px!important;
  height:27px!important;
  max-width:100%!important;
  padding:1px 5px!important;
  margin:0!important;
  font-size:11px!important;
  line-height:1!important;
  border-radius:6px!important;
}

/* Tablet / phone: do NOT hide top menu. Move it to its own row. */
@media(max-width:1050px){
  .site-header{
    display:grid!important;
    grid-template-columns:minmax(0,1fr)!important;
    gap:6px!important;
    align-items:center!important;
    justify-items:center!important;
    padding:7px 8px!important;
  }
  .site-logo{
    display:flex!important;
    justify-content:center!important;
    width:100%!important;
    min-width:0!important;
  }
  .site-logo img{
    width:135px!important;
    max-width:135px!important;
    height:auto!important;
  }
  .main-nav{
    display:block!important;
    visibility:visible!important;
    opacity:1!important;
    width:100%!important;
  }
  .main-nav ul{
    display:grid!important;
    grid-template-columns:repeat(4,minmax(0,1fr))!important;
    gap:4px!important;
    width:100%!important;
  }
  .main-nav li{min-width:0!important}
  .main-nav a{
    display:flex!important;
    align-items:center!important;
    justify-content:center!important;
    min-height:34px!important;
    padding:6px 5px!important;
    font-size:.82rem!important;
    white-space:normal!important;
    text-align:center!important;
    border-radius:8px!important;
  }
  .translate-row{
    display:flex!important;
    visibility:visible!important;
    opacity:1!important;
  }
}

@media(max-width:640px){
  .site-header{padding:6px!important;gap:5px!important}
  .site-logo img{width:118px!important;max-width:118px!important}
  .main-nav ul{
    grid-template-columns:repeat(2,minmax(0,1fr))!important;
    gap:4px!important;
  }
  .main-nav a{
    min-height:32px!important;
    padding:5px 4px!important;
    font-size:.8rem!important;
  }
  .translate-row{
    display:flex!important;
    visibility:visible!important;
    opacity:1!important;
    min-height:30px!important;
    padding:2px 4px!important;
    margin:3px 0 6px!important;
    gap:4px!important;
  }
  .translate-row>span:first-child{
    font-size:.7rem!important;
    white-space:nowrap!important;
  }
  #google_translate_element{
    display:flex!important;
    min-height:25px!important;
  }
  .goog-te-gadget-simple,.goog-te-combo{
    min-height:25px!important;
    height:25px!important;
    font-size:10px!important;
  }
}

@media(max-width:360px){
  .site-logo img{width:105px!important;max-width:105px!important}
  .main-nav a{font-size:.76rem!important}
  .translate-row>span:first-child{display:none!important}
  #google_translate_element{width:100%!important;justify-content:center!important}
}

/* RTL-safe menu */
[dir="rtl"] .main-nav ul{direction:rtl!important}