.site-header{position:sticky;top:0;z-index:50;min-height:80px;display:flex;align-items:center;justify-content:space-between;gap:24px;padding:16px max(28px,calc((100vw - 1280px)/2));background:rgba(11,16,21,.98);border-bottom:1px solid #26343e}.site-header .brand{display:flex;align-items:center;gap:9px;color:#edf2f6;font-size:24px;font-weight:600;white-space:nowrap}.site-header .site-ai-logo{width:34px;height:29px;object-fit:contain}.main-nav{display:flex;align-items:center;gap:18px}.main-nav a,.main-nav button{font:500 13px/1.5 Geist,sans-serif;color:#b9c6cf;white-space:nowrap;background:none;border:0;padding:0;cursor:pointer}.main-nav a:hover,.main-nav button:hover{color:#8fd0d3}.header-actions{display:flex;align-items:center;gap:18px}.participate-nav{font-size:14px}.participate-nav summary{padding:10px 14px;border:1px solid #344650;border-radius:8px}.participate-icon{display:none}.participate-menu a{display:block;padding:9px 12px;font-size:14px}.nav-toggle{display:none;background:none;border:0;width:30px;height:34px;padding:5px;cursor:pointer}.nav-toggle span{display:block;background:#b9c6cf;height:2px;margin:5px 0}.topic-back{display:inline-block;font-size:13px;margin-bottom:28px}.reader{padding-top:36px}@media(max-width:1199px){.nav-toggle{display:block}.site-header{padding:14px 24px}.main-nav{display:none;position:absolute;top:100%;left:0;right:0;background:#101820;padding:22px 28px;border-bottom:1px solid #344650;max-height:calc(100dvh - 80px);overflow:auto}.main-nav.is-open{display:flex;align-items:stretch;flex-direction:column;gap:0}.main-nav a,.main-nav button{text-align:left;padding:12px 0;font-size:15px}.site-header .brand{font-size:21px}}@media(max-width:450px){.site-header{gap:12px;padding:12px 20px}.header-actions{gap:12px}.participate-nav summary{padding:8px 10px}.site-header .site-ai-logo{width:28px;height:24px}}