/* Static landing pages (experiments, simulations, guide): fast, crawlable, same navy look as the app. */
:root { --strong: #fff; --head: #080d18; --tint: rgba(255, 255, 255, .07); --bg: #0e1626; --bg-2: #0a111f; --panel: #121b2e; --line: rgba(140, 175, 255, .1); --text: #eef3fc; --text-2: #c9d4ea; --muted: #8b9abb; --accent: #3b82f6; --accent-2: #60a5fa; --mint: #34d399; }
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text-2); font: 16px/1.7 "Segoe UI", "Microsoft YaHei", Helvetica, Arial, sans-serif; }
a { color: var(--accent-2); text-decoration: none; }
a:hover { text-decoration: underline; }
.top { height: 60px; display: flex; align-items: center; gap: 18px; padding: 0 22px; background: var(--head); border-bottom: 1px solid var(--line); }
.top .brand { display: flex; align-items: center; gap: 10px; color: var(--strong); font-weight: 700; font-size: 19px; }
.top .brand b { color: var(--accent-2); font-weight: 700; }
.top .brand img { width: 32px; height: 32px; }
.top nav { display: flex; gap: 16px; margin-left: auto; font-size: 14.5px; flex-wrap: wrap; }
.top nav a { color: var(--text-2); }
main { max-width: 860px; margin: 0 auto; padding: 26px 20px 60px; }
.crumbs { font-size: 13px; color: var(--muted); margin-bottom: 14px; }
.crumbs a { color: var(--muted); }
h1 { color: var(--strong); font-size: clamp(28px, 5vw, 40px); line-height: 1.15; margin: 6px 0 12px; }
h2 { color: var(--strong); font-size: 21px; margin: 34px 0 10px; }
h3 { color: var(--strong); font-size: 16px; margin: 0 0 4px; }
.lead { font-size: 18px; color: var(--text-2); }
.tag { display: inline-block; font-size: 12.5px; color: var(--mint); background: rgba(52, 211, 153, .1); border: 1px solid rgba(52, 211, 153, .3); padding: 1px 10px; border-radius: 12px; margin-right: 6px; }
.cta { display: inline-flex; align-items: center; gap: 8px; margin: 18px 0 6px; padding: 13px 24px; border-radius: 10px; background: var(--accent); color: #fff !important; font-weight: 600; font-size: 16px; box-shadow: 0 8px 22px rgba(59, 130, 246, .35); text-decoration: none !important; }
.cta:hover { background: var(--accent-2); }
.sub { font-size: 13px; color: var(--muted); }
ol.steps { counter-reset: s; list-style: none; padding: 0; display: grid; gap: 8px; }
ol.steps li { counter-increment: s; position: relative; padding: 10px 14px 10px 50px; background: var(--panel); border: 1px solid var(--line); border-radius: 10px; }
ol.steps li::before { content: counter(s); position: absolute; left: 12px; top: 10px; width: 26px; height: 26px; border-radius: 50%; background: var(--accent); color: #fff; font-size: 13px; font-weight: 700; display: grid; place-items: center; }
.box { background: var(--panel); border: 1px solid var(--line); border-left: 3px solid var(--mint); border-radius: 10px; padding: 14px 18px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 12px; }
.card { display: block; background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 14px 16px; color: var(--text-2); }
.card:hover { border-color: var(--accent); text-decoration: none; }
.card p { margin: 0; font-size: 14px; color: var(--muted); }
details { background: var(--panel); border: 1px solid var(--line); border-radius: 10px; margin-bottom: 8px; padding: 10px 14px; }
summary { cursor: pointer; color: var(--strong); }
table { width: 100%; border-collapse: collapse; background: var(--panel); border-radius: 10px; overflow: hidden; font-size: 15px; }
th, td { text-align: left; padding: 8px 12px; border-top: 1px solid var(--line); }
th { color: var(--strong); background: rgba(140, 175, 255, .06); }
.kbd { font-family: Consolas, monospace; font-size: 13px; padding: 0 5px; border: 1px solid var(--line); border-radius: 4px; }
.g-ui { color: var(--strong); background: var(--tint); border-radius: 4px; padding: 0 6px; }
.g-tip { margin: 12px 0; padding: 12px 14px; border-radius: 10px; background: rgba(59, 130, 246, .1); border-left: 3px solid var(--accent); }
.g-tip b:first-child { display: block; color: var(--accent-2); font-size: 12px; text-transform: uppercase; }
.g-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 10px; }
.g-card { display: block; background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 14px; color: var(--text-2); }
.g-num, .g-mock, .m-n { display: none; }
footer { border-top: 1px solid var(--line); background: var(--bg-2); padding: 26px 22px; text-align: center; font-size: 14px; color: var(--muted); }
footer a { color: var(--accent-2); }
@media (max-width: 640px) { .top { padding: 0 14px; gap: 10px; } .top nav { gap: 12px; font-size: 13.5px; flex-wrap: nowrap; } .top nav .wide { display: none; } main { padding: 18px 16px 50px; } }


/* element + molar mass reference pages */
.answer { font-size: 21px; color: var(--strong); background: rgba(52, 211, 153, .1); border: 1px solid rgba(52, 211, 153, .35); border-radius: 10px; padding: 14px 18px; margin: 12px 0; }
.answer b { color: var(--mint); }
.eq { font-family: Consolas, "SF Mono", monospace; color: var(--strong); background: rgba(59, 130, 246, .1); border-radius: 8px; padding: 10px 14px; overflow-x: auto; }
.fact { background: rgba(59, 130, 246, .1); border-radius: 10px; padding: 10px 14px; color: var(--text); }
.el-hero { display: grid; grid-template-columns: 1fr auto; gap: 22px; align-items: center; }
.bohr { width: 240px; height: 240px; background: radial-gradient(circle, rgba(59, 130, 246, .12), transparent 70%); border-radius: 50%; }
.props th { width: 42%; font-weight: 500; color: var(--muted); background: transparent; }
.props td { color: var(--strong); }
.props thead th { color: var(--strong); background: rgba(140, 175, 255, .06); width: auto; }
.props.mm td, .props.mm th { white-space: nowrap; }
.props .tot td { background: rgba(52, 211, 153, .08); }
.table-wrap { overflow-x: auto; border-radius: 10px; margin: 10px 0; }
.pc { display: inline-block; width: 60px; height: 7px; border-radius: 4px; background: var(--tint); margin-right: 8px; vertical-align: middle; overflow: hidden; }
.pc i { display: block; height: 100%; background: var(--mint); }
.sw { display: inline-block; width: 12px; height: 12px; border-radius: 50%; margin-right: 6px; vertical-align: -1px; }
.el-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.el-nav a:last-child { text-align: right; }
.faq details[open] summary { margin-bottom: 4px; }
.faq p { margin: 0; }
footer .explore { font-size: 15px; }
@media (max-width: 640px) { .el-hero { grid-template-columns: 1fr; justify-items: center; } .bohr { width: 220px; height: 220px; } .answer { font-size: 18px; } .props th { width: auto; } }

footer .updated { font-size: 12.5px; color: #5c6b8c; margin-top: 10px; }
.props tr th:only-child, .props th { vertical-align: top; }
.box p:last-child { margin-bottom: 0; }

:root[data-theme="light"] { --bg: #f4f6fb; --bg-2: #e9eef6; --panel: #ffffff; --line: rgba(15, 23, 42, .1); --text: #0f172a; --text-2: #334155; --muted: #5a6a84; --accent: #2563eb; --accent-2: #1d4ed8; --mint: #047857; --strong: #0b1220; --head: #ffffff; --tint: rgba(15, 23, 42, .05); color-scheme: light; }
:root[data-theme="light"] .top { box-shadow: 0 1px 0 var(--line); }
:root[data-theme="light"] .tag { background: rgba(5, 150, 105, .1); border-color: rgba(5, 150, 105, .35); }
:root[data-theme="light"] .answer { background: rgba(5, 150, 105, .08); }
:root[data-theme="light"] .bohr { background: radial-gradient(circle, #16233b, #0b1322 70%); }
.theme-toggle { margin-left: 4px; width: 34px; height: 34px; display: grid; place-items: center; border-radius: 17px; border: 1px solid var(--line); background: none; color: var(--text-2); cursor: pointer; }
.theme-toggle svg { width: 18px; height: 18px; }
.top nav { min-width: 0; }
.top .theme-toggle { flex: none; }
@media (max-width: 640px) { .top nav { overflow-x: auto; scrollbar-width: none; } .top nav::-webkit-scrollbar { display: none; } }