main.collab { max-width: 980px; margin: 0 auto; padding: 150px clamp(24px,4vw,68px) 80px; }
  .collab h1 { font-family: var(--display); font-size: clamp(36px,5vw,62px); font-weight: 500; line-height: 1.05; margin: 12px 0 22px; }
  .collab h1 span { color: var(--cyan); }
  .collab h2 { font-family: var(--display); font-weight: 500; font-size: 26px; margin: 64px 0 18px; padding-top: 22px; border-top: 1px solid var(--line); }
  .collab p, .collab li { color: #cad3dd; font-size: 16px; line-height: 1.7; }
  .lede { font-size: 19px !important; max-width: 760px; }
  .grid { display: grid; grid-template-columns: repeat(auto-fit,minmax(260px,1fr)); gap: 18px; }
  .card { border: 1px solid var(--line); border-radius: 14px; padding: 22px 24px; background: rgba(255,255,255,.02); }
  .card h3 { margin: 0 0 8px; font-family: var(--display); font-weight: 600; font-size: 17px; color: var(--paper); }
  .card .tag { color: var(--gold); font-size: 11px; letter-spacing: .14em; text-transform: uppercase; }
  ol.steps { counter-reset: s; list-style: none; padding: 0; }
  ol.steps li { counter-increment: s; position: relative; padding: 0 0 18px 52px; }
  ol.steps li::before { content: counter(s,decimal-leading-zero); position: absolute; left: 0; top: 0; color: var(--cyan); font-family: var(--display); font-weight: 600; }
  ol.steps strong, .collab li strong { color: var(--paper); }
  .note { border-left: 2px solid var(--gold); padding: 4px 0 4px 18px; }

.collab.zh p, .collab.zh li { font-family: "PingFang SC","Hiragino Sans GB",var(--sans); }

/* fixed full-page background; content scrolls over it */
html, body { background: transparent; }
html { background: var(--ink); }
body::before { content: ""; position: fixed; inset: 0; z-index: -2; background: url("/assets/scene-collaboration.webp") center / cover no-repeat; }
body::after { content: ""; position: fixed; inset: 0; z-index: -1; background: linear-gradient(180deg, rgba(7,17,31,.45) 0%, rgba(7,17,31,.75) 45%, rgba(7,17,31,.88) 100%); }
.card { background: rgba(7,17,31,.55); backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px); }
footer { position: relative; background: transparent; }

.card-link { display: block; text-decoration: none; transition: border-color .2s; }
.card-link:hover, .card-link:focus-visible { border-color: rgba(134,225,209,.6); }

.site-header { gap: 24px; }
.site-header nav { margin-left: auto; }
.lang-switch { display: inline-flex; flex: none; border: 1px solid var(--line); border-radius: 999px; overflow: hidden; font-size: 12px; letter-spacing: .08em; }
.lang-switch a { padding: 6px 12px; color: var(--muted); text-decoration: none; }
.lang-switch a[aria-current="true"] { background: rgba(134,225,209,.16); color: var(--cyan); }
.lang-switch a:hover:not([aria-current]) { color: var(--paper); }
@media (max-width: 820px) { .site-header nav { display: none; } }
.collab h2[id] { scroll-margin-top: 110px; }