/* Chemistry Lab v1.2: the Element Atlas wears the same header and phone navigation as the rest of the lab. */
.lab-header{position:sticky;top:0;z-index:20;background:var(--bg);height:78px;gap:24px}
.lab-header .brand{font-size:15px;letter-spacing:.15em}
.lab-header .brand-mark{font-size:40px}
.lab-header .brand small{font-size:13px;letter-spacing:.02em;margin-top:4px}
.lab-nav{display:flex;gap:3px;padding:4px;margin:0 auto;border:1px solid var(--line);border-radius:30px;background:var(--surface)}
.lab-nav a{display:flex;align-items:center;min-height:40px;padding:8px 19px;border-radius:24px;font-size:15px;color:var(--muted);transition:background .18s,color .18s}
.lab-nav a:hover{color:var(--accent)}
.lab-nav a[aria-current]{background:var(--raised);color:var(--accent);font-weight:700}
.lab-header .header-tools{margin-left:0}
.lab-header .icon-button{width:44px;height:44px}
.lab-mobile-nav{display:none}
.shell-lesson-link{display:inline-flex;align-items:center;gap:8px;min-height:44px;margin-top:8px;font-size:14px;color:var(--accent)}
.deeper-link{min-height:48px}
@media(max-width:1050px){.lab-nav a{padding-inline:12px}.lab-header .brand small{display:none}}
@media(max-width:850px){.lab-nav{display:none}.lab-header{height:68px;justify-content:space-between}}
@media(max-width:680px){
 body{padding-bottom:calc(78px + env(safe-area-inset-bottom,0px))}
 .lab-header .brand{font-size:12px;letter-spacing:.1em}.lab-header .brand-mark{font-size:29px}
 .lab-header .brand small{display:block;font-size:12px;letter-spacing:0}
 .lab-mobile-nav{position:fixed;bottom:0;left:0;right:0;z-index:30;display:grid;grid-template-columns:repeat(5,1fr);padding:7px 4px calc(7px + env(safe-area-inset-bottom,0px));background:var(--surface);border-top:1px solid var(--line)}
 .lab-mobile-nav a{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:4px;min-height:56px;font-size:12.5px;color:var(--muted);border-radius:12px}
 .lab-mobile-nav svg{width:21px;height:21px;stroke-width:1.5;fill:none;stroke:currentColor;stroke-linecap:round;stroke-linejoin:round}
 .lab-mobile-nav a[aria-current]{background:var(--raised);color:var(--accent);font-weight:700}
}