/* Ground Reaction Force / Movement Science */
.grf-page{--grf-ink:#080b10;--grf-paper:#f4f4f1;--grf-white:#fff;--grf-blue:#1748ec;--grf-muted:#5d646e;--grf-line:rgba(8,11,16,.14);background:var(--grf-paper);color:var(--grf-ink);font-family:Inter,"Noto Sans JP",system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;overflow:hidden}
.grf-page *{box-sizing:border-box}.grf-page a{text-decoration:none}.grf-wrap{width:min(1180px,calc(100% - 48px));margin:0 auto}.grf-hero{position:relative;min-height:720px;display:flex;align-items:flex-end;padding:170px 0 80px;background:linear-gradient(120deg,rgba(2,5,10,.98),rgba(2,5,10,.82) 58%,rgba(23,72,236,.42)),url('/media/ground-reaction-force/propulse-running-sequence.webp') center/cover no-repeat;color:#fff}.grf-hero:after{position:absolute;inset:0;background:linear-gradient(90deg,rgba(255,255,255,.045) 1px,transparent 1px),linear-gradient(rgba(255,255,255,.04) 1px,transparent 1px);background-size:52px 52px;content:"";pointer-events:none}.grf-hero .grf-wrap{position:relative;z-index:1}.grf-eyebrow{margin:0 0 18px;color:#8fa8ff;font-size:11px;font-weight:900;letter-spacing:.2em}.grf-hero h1{max-width:980px;margin:0;font-size:clamp(52px,7.6vw,104px);font-weight:900;line-height:.94;letter-spacing:-.065em}.grf-hero h1 span{display:block;margin-top:18px;color:#fff;font-size:clamp(24px,3.4vw,46px);font-weight:700;line-height:1.14;letter-spacing:-.035em}.grf-hero-lead{max-width:780px;margin:30px 0 0;padding-left:22px;border-left:3px solid var(--grf-blue);font-size:clamp(16px,1.65vw,20px);font-weight:500;line-height:1.95;color:rgba(255,255,255,.86)}.grf-tags{display:flex;flex-wrap:wrap;gap:8px;margin-top:30px}.grf-tags span{padding:8px 12px;border:1px solid rgba(255,255,255,.24);border-radius:999px;background:rgba(255,255,255,.07);font-size:10px;font-weight:800;letter-spacing:.08em}.grf-toc{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));margin-top:42px;border:1px solid rgba(255,255,255,.17);background:rgba(255,255,255,.1);gap:1px}.grf-toc a{display:flex;min-height:70px;align-items:center;padding:14px 16px;background:rgba(7,10,16,.86);color:#fff;font-size:11px;font-weight:800;line-height:1.45}.grf-toc a:hover{background:var(--grf-blue)}
.grf-section{padding:92px 0;border-bottom:1px solid var(--grf-line)}.grf-grid{display:grid;grid-template-columns:minmax(250px,.72fr) minmax(0,1.28fr);gap:72px;align-items:start}.grf-label{display:block;margin-bottom:15px;color:var(--grf-blue);font-size:10px;font-weight:900;letter-spacing:.19em}.grf-section h2{margin:0;font-size:clamp(35px,4.8vw,66px);font-weight:900;line-height:1.06;letter-spacing:-.055em}.grf-copy{min-width:0}.grf-copy>p{max-width:820px;margin:0 0 20px;color:#353b43;font-size:15px;line-height:2}.grf-copy>.grf-definition{color:var(--grf-ink);font-size:clamp(21px,2.3vw,31px);font-weight:800;line-height:1.55;letter-spacing:-.025em}.grf-note{max-width:840px;margin:30px 0;padding:22px 24px;border-left:4px solid var(--grf-blue);background:#e9edff;color:#252c36;font-size:14px;font-weight:650;line-height:1.85}.grf-card-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin-top:30px}.grf-card{min-height:205px;padding:24px;background:#fff;border:1px solid var(--grf-line)}.grf-card small{display:block;color:var(--grf-blue);font-size:9px;font-weight:900;letter-spacing:.14em}.grf-card h3{margin:14px 0 10px;font-size:21px;font-weight:850;line-height:1.25;letter-spacing:-.03em}.grf-card p{margin:0;color:var(--grf-muted);font-size:13px;line-height:1.8}.grf-table-wrap{margin-top:28px;overflow:auto}.grf-table{width:100%;min-width:720px;border-collapse:collapse;background:#fff}.grf-table th,.grf-table td{padding:16px 17px;border:1px solid var(--grf-line);text-align:left;vertical-align:top;line-height:1.65}.grf-table th{background:#eceeea;font-size:10px;font-weight:900;letter-spacing:.08em}.grf-table td{font-size:13px;color:#343a42}.grf-sequence{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));margin-top:30px;border:1px solid var(--grf-line);gap:1px;background:var(--grf-line)}.grf-sequence div{min-height:118px;padding:18px 16px;background:#fff;display:flex;flex-direction:column;justify-content:flex-end}.grf-sequence b{color:var(--grf-blue);font-size:10px;letter-spacing:.1em}.grf-sequence span{margin-top:7px;font-size:14px;font-weight:800}.grf-figure{margin:30px 0 0;background:#fff;border:1px solid var(--grf-line);overflow:hidden}.grf-figure img{display:block;width:100%;height:auto}.grf-figure figcaption{padding:16px 18px;color:#555e68;font-size:11px;line-height:1.8}.grf-figure figcaption strong{display:block;margin-bottom:4px;color:#0b1017;font-size:12px;letter-spacing:.06em}.grf-figure.is-dark{background:#0b1017;border-color:#242d38}.grf-figure.is-dark figcaption{color:#b8c1cc}.grf-figure.is-dark figcaption strong{color:#fff}.grf-visual-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-top:30px}.grf-dark{background:#090d13;color:#fff;border-bottom:0}.grf-dark .grf-label{color:#8fa8ff}.grf-dark .grf-copy>p,.grf-dark .grf-copy>.grf-definition{color:#d0d6df}.grf-dark .grf-card{background:#111722;border-color:#283140}.grf-dark .grf-card h3{color:#fff}.grf-dark .grf-card p{color:#aeb8c5}.grf-dark .grf-sequence{border-color:#2b3542;background:#2b3542}.grf-dark .grf-sequence div{background:#111722}.grf-dark .grf-sequence span{color:#fff}.grf-links{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px;margin-top:30px}.grf-links a{display:flex;min-height:112px;flex-direction:column;justify-content:space-between;padding:18px;border:1px solid #303a48;color:#fff;transition:background .2s ease,border-color .2s ease}.grf-links a:hover{background:#121a26;border-color:#5276ff}.grf-links small{color:#8fa8ff;font-size:9px;font-weight:900;letter-spacing:.12em}.grf-links strong{font-size:13px}.grf-manual{display:grid;grid-template-columns:minmax(0,1fr) minmax(300px,.72fr);gap:34px;align-items:center;margin-top:30px}.grf-manual-copy{padding:28px;background:#fff;border:1px solid var(--grf-line)}.grf-manual-copy h3{margin:0 0 14px;font-size:25px;font-weight:900;line-height:1.2;letter-spacing:-.035em}.grf-manual-copy p{margin:0 0 14px;color:#4a525c;font-size:13px;line-height:1.9}.grf-manual-copy ul{display:grid;gap:9px;margin:20px 0 0;padding:0;list-style:none}.grf-manual-copy li{padding-left:18px;position:relative;color:#2b323b;font-size:13px;line-height:1.7}.grf-manual-copy li:before{position:absolute;left:0;top:.72em;width:6px;height:6px;border-radius:50%;background:var(--grf-blue);content:""}.grf-video{position:relative;aspect-ratio:16/9;margin-top:30px;background:#000;overflow:hidden}.grf-video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}.grf-actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:18px}.grf-button{display:inline-flex;min-height:48px;align-items:center;justify-content:center;padding:12px 17px;border:1px solid var(--grf-ink);background:#fff;color:var(--grf-ink);font-size:11px;font-weight:850}.grf-button.primary{background:var(--grf-blue);border-color:var(--grf-blue);color:#fff}.grf-faq details{padding:22px 2px;border-top:1px solid var(--grf-line);background:transparent}.grf-faq details:last-child{border-bottom:1px solid var(--grf-line)}.grf-faq summary{cursor:pointer;font-size:14px;font-weight:850;line-height:1.6}.grf-faq details p{max-width:850px;margin:13px 0 0;color:#4a525c;font-size:13px;line-height:1.9}.grf-refs{padding-left:20px}.grf-refs li{margin-bottom:13px;color:#4a525c;font-size:12px;line-height:1.8}.grf-refs a{color:#1748ec;text-decoration:underline;text-underline-offset:3px}.grf-disclaimer{margin-top:25px;color:#69717b!important;font-size:11px!important}.grf-closing{padding:76px 0;background:#1748ec;color:#fff}.grf-closing-grid{display:grid;grid-template-columns:1fr auto;gap:30px;align-items:end}.grf-closing h2{margin:0;font-size:clamp(38px,5.4vw,72px);font-weight:900;line-height:1;letter-spacing:-.055em}.grf-closing p{max-width:650px;margin:18px 0 0;color:rgba(255,255,255,.86);font-size:14px;line-height:1.8}.grf-closing .grf-button{border-color:#fff}
@media(max-width:1024px){.grf-hero{min-height:680px;padding-top:150px}.grf-grid{grid-template-columns:1fr;gap:30px}.grf-card-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.grf-toc{grid-template-columns:repeat(2,minmax(0,1fr))}.grf-links{grid-template-columns:repeat(2,minmax(0,1fr))}.grf-manual{grid-template-columns:1fr 1fr}.grf-closing-grid{grid-template-columns:1fr}.grf-sequence{grid-template-columns:repeat(5,minmax(125px,1fr));overflow-x:auto}}
@media(max-width:760px){.grf-wrap{width:min(100% - 34px,1180px)}.grf-hero{min-height:620px;padding:135px 0 52px;background-position:68% center}.grf-hero h1{font-size:clamp(47px,13vw,72px)}.grf-hero h1 span{font-size:clamp(23px,7vw,34px)}.grf-hero-lead{font-size:14px;line-height:1.85}.grf-toc{grid-template-columns:1fr 1fr}.grf-toc a{min-height:58px;padding:11px 12px;font-size:10px}.grf-section{padding:64px 0}.grf-section h2{font-size:clamp(34px,10vw,50px)}.grf-card-grid,.grf-visual-grid,.grf-manual,.grf-links{grid-template-columns:1fr}.grf-card{min-height:0}.grf-table th,.grf-table td{padding:13px}.grf-manual-copy{padding:22px}.grf-closing{padding:58px 0}}
@media(max-width:520px){.grf-wrap{width:min(100% - 28px,1180px)}.grf-hero{min-height:600px}.grf-toc{grid-template-columns:1fr}.grf-tags{gap:6px}.grf-tags span{padding:7px 9px}.grf-sequence{grid-template-columns:1fr;overflow:visible}.grf-sequence div{min-height:78px}.grf-actions{display:grid}.grf-button{width:100%}.grf-copy>p{font-size:14px}}


/* 2026-08-30 hero alignment with /spinal-engine */
.grf-page .grf-hero{min-height:720px;position:relative;background:#05080c;color:#fff;display:flex;align-items:flex-end;overflow:hidden;padding:0}
.grf-page .grf-hero-media{position:absolute;inset:0;background:linear-gradient(90deg,rgba(3,6,10,.96) 0%,rgba(3,6,10,.72) 43%,rgba(3,6,10,.30) 100%),url('/media/ground-reaction-force/ground-reaction-force-hero.webp') center center/cover no-repeat;transform:scale(1.01);filter:grayscale(12%)}
.grf-page .grf-hero-grid{position:absolute;inset:0;background-image:linear-gradient(rgba(255,255,255,.04) 1px,transparent 1px),linear-gradient(90deg,rgba(255,255,255,.04) 1px,transparent 1px);background-size:80px 80px;mask-image:linear-gradient(to right,#000,transparent 72%);-webkit-mask-image:linear-gradient(to right,#000,transparent 72%)}
.grf-page .grf-hero-copy{position:relative;z-index:2;width:min(1420px,calc(100% - 84px));margin:0 auto;padding:170px 0 86px}
.grf-page .grf-kicker{display:flex;align-items:center;gap:18px;color:#c8ced6;font-size:13px;line-height:1.3;letter-spacing:.22em;font-weight:800;text-transform:uppercase;margin:0}
.grf-page .grf-kicker span{width:58px;height:3px;background:#1684ff;display:block;flex:0 0 auto}
.grf-page .grf-hero h1{font-size:clamp(68px,8.7vw,142px);line-height:.80;letter-spacing:-.075em;font-weight:900;margin:40px 0 42px;max-width:1180px;color:#fff}
.grf-page .grf-hero h1 em{font-style:normal;color:#1684ff;-webkit-text-stroke:1px #fff}
.grf-page .grf-hero-lead{font-size:clamp(18px,1.55vw,25px);line-height:1.9;max-width:980px;border-left:4px solid #1684ff;padding-left:34px;color:#e2e6eb;margin:0}
.grf-page .grf-tags,.grf-page .grf-toc{display:none!important}
@media(max-width:1050px){.grf-page .grf-hero{min-height:650px}.grf-page .grf-hero-media{background-position:58% center}}
@media(max-width:680px){.grf-page .grf-hero{min-height:610px}.grf-page .grf-hero-copy{width:calc(100% - 40px);padding:145px 0 58px}.grf-page .grf-kicker{font-size:10px;gap:12px;letter-spacing:.16em}.grf-page .grf-kicker span{width:34px}.grf-page .grf-hero h1{font-size:clamp(50px,16.5vw,72px);line-height:.84;letter-spacing:-.065em;margin:30px 0 32px;max-width:100%}.grf-page .grf-hero-lead{font-size:16px;line-height:1.85;padding-left:20px}.grf-page .grf-hero-media{background-position:60% center}}