:root{color-scheme:light}
.theme-toggle{flex-shrink:0;display:grid;place-items:center;width:40px;height:40px;padding:0;border:1px solid var(--line);border-radius:9px;background:var(--white);color:var(--ink);font-size:24px;line-height:1}
.theme-toggle:hover{border-color:var(--blue);color:var(--blue)}
@media screen{
  :root[data-theme=dark]{color-scheme:dark;--ink:#e3ecf7;--muted:#a8b8ca;--blue:#83b6ff;--teal:#66d6be;--line:#33465b;--paper:#101923;--white:#192635}
  [data-theme=dark] .site-header{background:rgba(16,25,35,.97)}
  [data-theme=dark] :is(.skip,.menu-toggle,.sidebar-toggle,.hero-visual,.route-item,.lesson-card,.footer,.progress-box,.article,.lesson-navigation a,.search-input,.search-result,.generator-controls,.generator-output,.generator-notes,.generator-fields input,.generator-presets button){background:var(--white);color:var(--ink)}
  [data-theme=dark] .button{background:#235eae;border-color:#83b6ff;color:#fff}
  [data-theme=dark] .button:hover{background:#2c70cb}
  [data-theme=dark] .button.secondary{background:var(--white);border-color:var(--line);color:var(--ink)}
  [data-theme=dark] .button.secondary:hover{background:#253b53}
  [data-theme=dark] .brand-mark{background:#235eae}
  [data-theme=dark] :is(.feature-band,th,.article :not(pre)>code){background:#223348}
  [data-theme=dark] :is(td,.toc a){color:#bccde0}
  [data-theme=dark] .sidebar a.active{background:#213953}
  [data-theme=dark] .article .formula{background:#1c324b;color:#c1dcff}
  [data-theme=dark] :is(.learning-goals,.article details,#model-status,.live-label){background:#173630;border-color:#34594f}
  [data-theme=dark] :is(.learning-goals strong,.article summary){color:#83dfc5}
  [data-theme=dark] :is(.search-input,.generator-fields input){border-color:#526b85}
  [data-theme=dark] .generator-output svg{background:#121e2b}
  [data-theme=dark] .generator-output svg text{fill:#bccde0}
  [data-theme=dark] .generator-output svg line[stroke="#dce4ed"]{stroke:#33465b}
  [data-theme=dark] .generator-output svg line[stroke="#a35b00"]{stroke:#efb763}
  [data-theme=dark] .generator-output svg path[stroke="#155fce"]{stroke:#83b6ff}
  [data-theme=dark] .generator-output svg path[stroke="#13897c"]{stroke:#66d6be}
  [data-theme=dark] .generator-output svg path[stroke="#9857aa"]{stroke:#d79bea}
  /* Static scientific figures retain their original backgrounds and colour keys. */
  [data-theme=dark] :is(.article figure img,.hero-visual img){background:#fff;border-radius:6px}
}
@media(max-width:1100px) and (min-width:761px){.header-inner{gap:12px}.nav{gap:12px}.nav a{font-size:13px}.brand{font-size:14px}}
@media(min-width:761px) and (max-width:1000px){[data-theme] .header-inner{flex-wrap:wrap;padding:12px 0}[data-theme] .theme-toggle{margin-left:auto}[data-theme] .menu-toggle{display:block;margin-left:0}[data-theme] .nav{display:none;flex-basis:100%;margin-left:0;padding:8px 0;flex-wrap:wrap}[data-theme] .nav.open{display:flex}}
@media(max-width:760px){.header-inner{gap:8px}.theme-toggle{margin-left:auto}.menu-toggle{margin-left:0}.nav{margin-left:0}}
@media(max-width:420px){.header-inner>.brand{font-size:12px;gap:7px;letter-spacing:1px}.header-inner .brand-mark{width:28px;height:28px}.header-inner .brand small{display:none}.theme-toggle{width:34px;height:36px}.menu-toggle{padding:6px 8px;font-size:13px}}
@media print{.theme-toggle{display:none}:root{color-scheme:light}}