/* Compatibility layer: preserves lesson markup, IDs, scripts and storage keys. */
:root[data-ph-article]{
  color-scheme:light;
  --bg:#f3f7fc;--bg2:#edf3fa;--bg3:#e5edf7;--bg4:#dce7f4;--bg-2:#edf3fa;--bg-alt:#edf3fa;--bg-deep:#f1f5fb;
  --bg-primary:#f3f7fc;--bg-secondary:#edf3fa;--bg-tertiary:#e4edf8;--bg-elevated:#eaf1fa;
  --bg-card:#ffffffd9;--bg-card-hover:#fff;--bg-section:#ffffffb3;
  --surface:#ffffffdf;--surface-2:#edf3fb;--surface-alt:#edf3fa;--panel:#ffffffde;--panel-2:#ecf3fc;--paper:#f7faff;
  --text:#172335;--text-primary:#172335;--text-bright:#172335;--text-secondary:#4c5d74;--text-tertiary:#53667d;
  --text-muted:#53667d;--text-dim:#52647a;--text-faint:#53667d;--text2:#4c5d74;--text3:#53667d;
  --ink:#172335;--ink-soft:#435872;--ink-dim:#52647a;--ink-faint:#52647a;
  --line:#ccd9e8;--line-soft:#e0e8f2;--border:#ccd9e8;--border-color:#ccd9e8;--border-light:#e0e8f2;--border-bright:#9eafc5;--border-accent:#9eafc5;--border-hover:#9eafc5;--grid:#e4edf8;--rule:#ccd9e8;
  --accent:#075fd4;--accent-hover:#064caf;--accent-dim:#075fd422;--accent-glow:#075fd419;--accent-green:#18734c;--accent-cyan:#08748c;--accent-blue:#075fd4;--accent-purple:#7442b0;--accent-yellow:#856200;--accent-orange:#a85406;--accent-red:#b82c3f;
  --green:#18734c;--green2:#12623f;--green3:#12623f;--green-dim:#18734c;--green-glow:#18734c18;--cyan:#08748c;--cyan-deep:#075c70;--purple:#7442b0;--violet:#7442b0;--amber:#925906;--amber-deep:#774900;--yellow:#856200;--orange:#a85406;--red:#b82c3f;--rose:#b33361;--sky:#086d9e;--emerald:#18734c;
  --night-deep:#f3f5fc;--night-mid:#eaf0fa;--night-soft:#e0e8f5;--moon-glow:#555086;--lavender:#6b57a1;--lavender-soft:#6b57a1;--warm-gold:#856200;--sleep-blue:#396595;--dream-teal:#247376;
  --symp-primary:#b82c3f;--para-primary:#08748c;--accent-gold:#856200;
  --font:var(--ph-system);--font-body:var(--ph-system);--font-heading:var(--ph-system);--font-display:var(--ph-system);--font-sans:var(--ph-system);--sans:var(--ph-system);--disp:var(--ph-system);
  --mono:ui-monospace,SFMono-Regular,Consolas,monospace;--font-mono:ui-monospace,SFMono-Regular,Consolas,monospace;
  --radius:22px;--shadow-sm:0 2px 12px #2c578610;--shadow-md:0 10px 30px -20px #2c57863b;
}
body.ph-article{background:linear-gradient(145deg,#f7fbff,#eef4fc 45%,#f5f3fc);color:#172335;font-family:var(--ph-system);min-width:280px;margin:0}
body.ph-article::before,body.ph-article::after{display:none!important}
.ph-article :is(.grain,.noise,.bg-grid,.stars-container,.moon){display:none!important}
.ph-article :is(.hero,header:not(.ph-header),.sidebar){background-image:none}
.ph-article :is(.card,.panel,.topic-card,.device-card,.lesson-card,.task,.exercise,.exercise-card,.section-card){border-color:#ccd9e8;box-shadow:0 10px 30px -24px #376b9e55;border-radius:20px}
.ph-article :is(.card,.panel,.topic-card,.device-card,.lesson-card,.exercise-card,.section-card){background-color:#ffffffd9}
.ph-article :is(.topbar,.top,.tab-bar,.statusbar,.header,.controls,.sidebar){background:#f6faffed;color:#172335;border-color:#ccd9e8}
.ph-article>nav,.ph-article .topnav,.ph-article .status-bar{position:sticky;top:0;background:#f6faffed;color:#172335;border-color:#ccd9e8;backdrop-filter:blur(14px)}
.ph-article>nav a,.ph-article .topnav a{color:#345171}
.ph-article :is(.hero-sub,.hero-desc,.subtitle,.logo-sub){color:#4c5d74}
.ph-article :is(.hero h1,.hero-title,.logo-text){text-shadow:none}
.ph-article :is(pre,.code-block,.terminal,.terminal-body,.term-body,.code-body){background:#172335;color:#e9f1fc;--text:#e9f1fc;--text-primary:#e9f1fc;--text-secondary:#b2c4db;--text-dim:#b2c4db;--text-muted:#b2c4db;--ink:#e9f1fc;--ink-soft:#b2c4db;--green:#78e2a6;--cyan:#7fdded;--accent:#8dbfff;--border:#3c506b;--line:#3c506b}
.ph-article pre{max-width:100%;overflow:auto}
.ph-article pre code{color:inherit;background:transparent}
.ph-article img{max-width:100%;height:auto}
.ph-article :is(input,textarea,select):focus-visible,.ph-article :is(a,button,summary):focus-visible{outline:3px solid #075fd4;outline-offset:3px}
.ph-article :is(h1,h2,h3,section,[id]){scroll-margin-top:85px}
.ph-article .ph-notice{margin:24px auto;max-width:1050px;border-radius:14px}
.document-hidden body.ph-article *{animation-play-state:paused!important}
@media(max-width:640px){.ph-article .ph-breadcrumb{font-size:12px}.ph-article>nav{padding-inline:16px;flex-wrap:wrap;gap:12px}.ph-article :is(h1,.hero h1){overflow-wrap:anywhere}}
@media(prefers-reduced-motion:reduce){.ph-article *,.ph-article *::before,.ph-article *::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important;scroll-behavior:auto!important}}
@media print{body.ph-article{background:white;color:black}.ph-article::before,.ph-article::after{display:none}.ph-article :is(.card,.panel,.task,.exercise){box-shadow:none;backdrop-filter:none}.ph-notice{display:none}}