*{box-sizing:border-box;margin:0;padding:0}
:root{color-scheme:dark;--bg:#101820;--panel:#17242e;--panel-soft:rgba(23,36,46,.88);--text:#f4f1e8;--muted:#b8c2c8;--accent:#ffd166;--sea:#4cc9f0;--ink:#0b1116;--line:rgba(255,255,255,.1);--line-strong:rgba(255,255,255,.18)}
body{font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;background:linear-gradient(180deg,#0d2735 0,#101820 42%,#171717 100%);color:var(--text);line-height:1.6;text-rendering:optimizeLegibility}
img{max-width:100%;height:auto}
header.hd,nav.mn,main.ct,footer.ft{width:min(960px,92%);margin:auto}
header.hd{padding:4rem 0 2rem;text-align:center}
header.hd span{display:inline-block;margin-bottom:1rem;padding:.35rem .8rem;border:1px solid var(--sea);border-radius:999px;color:var(--sea);font-size:.85rem;letter-spacing:.08em;text-transform:uppercase}
h1{font-size:clamp(2.3rem,7vw,5.8rem);line-height:.95;letter-spacing:-.06em}
header.hd p{max-width:720px;margin:1.5rem auto 0;color:var(--muted);font-size:1.15rem}
nav.mn{position:sticky;top:0;z-index:10;padding:.8rem 0;background:rgba(16,24,32,.9);backdrop-filter:blur(12px)}
nav.mn ol{display:flex;flex-wrap:wrap;justify-content:center;gap:.5rem;list-style:none}
nav.mn a{display:block;padding:.55rem .85rem;border-radius:.4rem;color:var(--text);text-decoration:none;transition:background .2s ease,color .2s ease}
nav.mn a:hover,nav.mn a:focus{background:var(--panel);color:var(--accent)}
main.ct{display:block;padding:2rem 0 4rem}
section{margin:1.2rem 0;padding:clamp(1.4rem,4vw,3rem);border:1px solid var(--line);border-radius:1rem;background:var(--panel-soft);box-shadow:0 20px 60px rgba(0,0,0,.2)}
h2{margin-bottom:1rem;font-size:clamp(1.6rem,4vw,2.6rem);line-height:1.1}
p+p{margin-top:1rem}
strong{color:var(--accent)}
code{padding:.15rem .35rem;border-radius:.25rem;background:var(--ink);color:#a7f3d0}
dl{display:grid;gap:1rem;margin-top:1.2rem}
dt{font-weight:800;color:var(--sea)}
dd{color:var(--muted)}
blockquote{margin-top:1.3rem;padding:1rem 1.2rem;border-left:.3rem solid var(--accent);background:#111a21;font-size:1.08rem}
#equation p{font-size:clamp(1.15rem,3vw,1.55rem);text-align:center}
#oath{text-align:center}
#oath p{max-width:680px;margin:0 auto 1rem}
#oath img{display:inline-block;filter:drop-shadow(0 8px 22px rgba(0,0,0,.28))}
#oath a{display:inline-block;margin-top:.8rem;padding:.8rem 1.1rem;border-radius:.5rem;background:var(--accent);color:#171717;font-weight:800;text-decoration:none;transition:transform .2s ease,box-shadow .2s ease,filter .2s ease}
#oath a:hover,#oath a:focus{transform:translateY(-1px);box-shadow:0 14px 30px rgba(0,0,0,.22);filter:saturate(1.06)}
footer.ft{padding:2rem 0 3rem;text-align:center;color:var(--muted);font-size:.9rem}
small{display:block;margin-top:.5rem}
.lang-switch{display:flex;justify-content:center;gap:.75rem;margin-top:1.25rem;flex-wrap:wrap}
.lang-switch a{display:inline-flex;align-items:center;gap:.55rem;padding:.55rem .95rem;border:1px solid var(--line-strong);border-radius:999px;color:var(--text);text-decoration:none;font-size:.95rem;letter-spacing:.01em;background:rgba(255,255,255,.03);transition:border-color .2s ease,color .2s ease,background .2s ease,transform .2s ease}
.lang-switch a::before{display:inline-flex;align-items:center;justify-content:center;min-width:2.2rem;padding:.18rem .45rem;border-radius:999px;font-size:.72rem;font-weight:800;letter-spacing:.08em;text-transform:uppercase;background:rgba(255,255,255,.08);color:var(--muted);content:attr(lang)}
.lang-switch a:hover,.lang-switch a:focus{border-color:var(--sea);color:var(--sea);background:rgba(76,201,240,.08);transform:translateY(-1px)}
.lang-switch a[aria-current="true"]{background:var(--sea);border-color:var(--sea);color:var(--ink);font-weight:800}
.lang-switch a[aria-current="true"]::before{background:rgba(11,17,22,.14);color:var(--ink)}
.lang-switch a[lang="fr"]::before{content:"FR"}
.lang-switch a[lang="en"]::before{content:"EN"}
a:focus-visible{outline:2px solid var(--sea);outline-offset:3px}
@media (max-width:640px){
nav.mn{padding:.65rem 0}
section{margin:1rem 0}
.lang-switch a{width:100%;justify-content:center}
}