:root{color-scheme:light;--ink:#152439;--muted:#52647a;--navy:#102d4e;--blue:#186fba;--pale:#f2f7fb;--line:#d9e4ed;--white:#fff;--focus:#e5a400}
*{box-sizing:border-box}
html{font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;scroll-behavior:smooth}
body{margin:0;color:var(--ink);background:var(--white);line-height:1.55}
button,input,select{font:inherit}
a{color:#0a5f9e}
a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid var(--focus);outline-offset:3px}
[hidden]{display:none!important}
.container{width:min(100% - 36px,1080px);margin-inline:auto}
.skip-link{position:absolute;left:16px;top:-100px;background:var(--white);padding:12px;z-index:10}.skip-link:focus{top:12px}
.site-header{border-bottom:1px solid var(--line);background:#fff}.header-inner{min-height:68px;display:flex;align-items:center;justify-content:space-between;gap:16px}
.brand{display:inline-flex;gap:8px;align-items:center;color:var(--navy);font-weight:800;font-size:1.3rem;text-decoration:none;white-space:nowrap;letter-spacing:-.04em}
.brand img{display:block;width:clamp(145px,37vw,218px);height:auto}
.brand-mark{display:grid;place-items:center;background:var(--navy);color:#fff;border-radius:12px;width:34px;height:34px;font-size:1.1rem}
.site-menu { position: relative; z-index: 20; }
.site-menu summary { display: flex; align-items: center; gap: 8px; min-height: 44px; padding: 8px 10px; border: 1px solid var(--line); border-radius: 9px; color: var(--navy); font-size: .9rem; font-weight: 700; cursor: pointer; list-style: none; user-select: none; }
.site-menu summary::-webkit-details-marker { display: none; }
.site-menu summary::before { content: "☰"; font-size: 1.2rem; line-height: 1; }
.site-menu[open] summary { background: var(--pale); }
.site-menu summary:focus-visible { outline: 3px solid var(--focus); outline-offset: 3px; }
.menu-links { position: absolute; right: 0; top: calc(100% + 8px); width: min(360px, calc(100vw - 36px)); max-height: calc(100vh - 100px); max-height: calc(100dvh - 100px); overflow-y: auto; overscroll-behavior: contain; display: grid; gap: 10px; padding: 10px; background: #fff; border: 1px solid var(--line); border-radius: 14px; box-shadow: 0 14px 36px #183c6026; }
.menu-group { --menu-accent: #186fba; --menu-ink: #125d99; --menu-tint: #edf5fc; --menu-line: #c9ddeb; border: 1px solid var(--menu-line); border-left: 4px solid var(--menu-accent); border-radius: 10px; padding: 4px 6px 6px; }
.menu-group-speed { --menu-accent: #d6a12f; --menu-ink: #855000; --menu-tint: #fff5dc; --menu-line: #e9d6a7; }
.menu-group-area { --menu-accent: #326645; --menu-ink: #305b41; --menu-tint: #edf8ee; --menu-line: #bbd6c2; }
.menu-group h2 { margin: 0; font-size: 1rem; line-height: 1.3; letter-spacing: 0; }
.menu-links a { display: flex; align-items: center; min-height: 44px; padding: 9px 12px; border-radius: 7px; color: var(--navy); font-size: .92rem; font-weight: 550; line-height: 1.3; text-decoration: none; white-space: normal; }
.menu-links .menu-category { justify-content: space-between; gap: 12px; color: var(--menu-ink); font-size: 1rem; font-weight: 800; }
.menu-category span { font-size: 1.1rem; }
.menu-children { list-style: none; margin: 2px 0 2px 14px; padding: 0 0 0 8px; border-left: 1px solid var(--menu-line); }
.menu-children li { margin: 0; padding: 0; }
.menu-group a:hover, .menu-group a[aria-current="page"] { background: var(--menu-tint); color: var(--menu-ink); }
.menu-group a[aria-current="page"] { font-weight: 800; box-shadow: inset 3px 0 var(--menu-accent); }
.menu-group-active .menu-category { background: var(--menu-tint); }
.menu-site-links { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 6px; padding-top: 4px; border-top: 1px solid var(--line); }
.menu-site-links a:hover, .menu-site-links a[aria-current="page"] { background: var(--pale); color: #0a5f9e; }
@media (max-width: 380px) { .menu-links { padding: 8px; } .menu-links a { padding-inline: 9px; } }

.hero{padding:30px 0 46px;background:linear-gradient(150deg,#f6faff,#eaf3f9)}.hero-grid{display:grid;gap:28px}.intro{align-self:center}
.eyebrow{text-transform:uppercase;letter-spacing:.12em;color:#176aa9;font-size:.76rem;font-weight:800;margin:0 0 12px}
h1,h2,h3{line-height:1.16;letter-spacing:-.035em;color:var(--navy)}h1{font-size:clamp(2.15rem,7vw,4.4rem);margin:0 0 17px}h2{font-size:clamp(1.45rem,4vw,2.1rem);margin:0 0 16px}h3{font-size:1.2rem;margin:0 0 10px}
.lede{font-size:1.08rem;max-width:56ch;color:var(--muted);margin:0}.breadcrumbs{font-size:.88rem;margin-bottom:27px;color:var(--muted)}.breadcrumbs a{color:inherit}
.tool-panel{background:var(--white);border:1px solid var(--line);box-shadow:0 14px 36px #183c6012;border-radius:20px;padding:22px}.tool-panel>p{margin:-7px 0 16px;color:var(--muted)}
.field{margin-bottom:16px}.field label{display:block;font-weight:700;margin-bottom:5px;font-size:.94rem}.field input,.field select{display:block;width:100%;min-height:48px;padding:10px 12px;border-radius:9px;border:1px solid #9dafc0;background:#fff;color:var(--ink)}.field input:disabled{background:#f2f2f2}.field-hint{font-size:.81rem;color:var(--muted);margin:5px 0 0}
.field-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0 12px}.unit-field{max-width:100%}.button{width:100%;min-height:51px;border:0;border-radius:10px;background:var(--blue);color:#fff;font-weight:750;cursor:pointer;padding:11px 16px}.button:hover{background:#0f588f}
.result{margin-top:20px;border-radius:12px;padding:16px;background:#eaf6f0;border:1px solid #aad6bd;overflow-wrap:anywhere}.result-label{margin:0;color:#245f3d;font-weight:700}.result-main{font-size:clamp(1.7rem,6vw,2.4rem);font-weight:800;line-height:1.15;margin:4px 0 8px}.result-extra{font-size:.9rem;margin:0;color:#264a39}.form-error{color:#ad2424;font-weight:700;margin:14px 0 0}
.shape-guide{margin-top:23px}.shape-guide img{display:block;width:min(100%,280px);height:auto}.section{padding:44px 0 60px}.link-card{display:flex;justify-content:space-between;align-items:center;gap:16px;text-decoration:none;border:1px solid var(--line);border-radius:16px;padding:20px;max-width:650px}.link-card:hover{border-color:var(--blue)}.link-card strong,.link-card small{display:block}.link-card strong{font-size:1.12rem}.link-card small{color:var(--muted);margin-top:3px}
.shape-links{padding:26px 0 30px;border-bottom:1px solid var(--line)}
.shape-links h2{font-size:1.16rem;letter-spacing:0;margin:0 0 14px}
.shape-links-scroll{display:flex;gap:10px;overflow-x:auto;overscroll-behavior-inline:contain;scroll-snap-type:x proximity;padding:2px 2px 12px}
.shape-links-scroll:focus-visible{outline:3px solid var(--focus);outline-offset:2px}
.shape-link{flex:0 0 122px;min-height:112px;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:4px;padding:8px 6px;border:1px solid var(--line);border-radius:12px;color:var(--navy);font-size:.84rem;font-weight:700;line-height:1.2;text-align:center;text-decoration:none;scroll-snap-align:start}
.shape-link img{display:block;width:82px;height:60px;object-fit:contain}
.shape-link:hover,.shape-link[aria-current="page"]{border-color:var(--blue);background:var(--pale)}
.content-block{padding:48px 0}.content-block-tinted{background:var(--pale)}
.content-block p{max-width:65ch}.content-block h2{max-width:22ch}.content-block p:last-child{margin-bottom:0}
.content-split{display:grid;gap:26px;align-items:center}.text-link{display:inline-block;font-weight:700;margin-top:8px}
.formula-panel{padding:28px;border:1px solid var(--line);border-radius:18px;background:#fff;box-shadow:0 10px 28px #183c600c;display:grid;gap:12px}
.formula-panel-label{color:var(--muted);font-weight:700;font-size:.85rem}.formula-panel strong{color:var(--navy);font-size:clamp(1.6rem,6vw,2.25rem);letter-spacing:-.04em}.formula-panel span:last-child{color:var(--muted)}
.info-grid{display:grid;gap:14px;margin-top:24px}.info-card{display:flex;flex-direction:column;align-items:flex-start;gap:10px;padding:22px;border:1px solid var(--line);border-radius:16px;background:#fff;color:var(--ink);text-decoration:none}
.info-card:hover{border-color:var(--blue)}.info-card h3{margin:0}.info-card p{margin:0;color:var(--muted)}.info-card>span{margin-top:auto;color:#0a5f9e;font-weight:700}
.tips-grid{display:grid;gap:18px;margin-top:24px}.tips-grid>div{border-left:3px solid var(--blue);padding-left:16px}.tips-grid strong{color:var(--navy)}.tips-grid p{margin:6px 0 0;color:var(--muted)}
.article{max-width:850px}.article>p{max-width:75ch}.formula-grid{display:grid;gap:15px;margin-top:24px}.formula-grid section{border:1px solid var(--line);border-radius:14px;padding:20px}.formula-grid p{margin:8px 0 0}.note{color:var(--muted);font-size:.91rem;margin-top:24px}
.site-footer{border-top:1px solid var(--line);padding:24px 0;color:var(--muted);font-size:.87rem}.footer-inner{display:flex;justify-content:space-between;align-items:center;gap:15px;flex-wrap:wrap}.footer-inner p{margin:0}
.ad-region{margin:24px auto 8px;text-align:center}.ad-label{color:var(--muted);font-size:.72rem;margin:0 0 8px}.ad-unit{display:block;min-height:120px}
@media(min-width:700px){.hero{padding:65px 0 75px}.hero-grid{grid-template-columns:minmax(0,1fr) minmax(350px,460px);gap:45px}.tool-panel{padding:30px}.field-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.formula-grid{grid-template-columns:repeat(3,minmax(0,1fr))}.section{padding:65px 0 85px}.shape-links{padding:30px 0 34px}.shape-links-scroll{display:grid;grid-template-columns:repeat(7,minmax(0,1fr));overflow:visible;padding-bottom:0}.shape-link{min-width:0}.shape-link img{width:90px;height:66px}}
@media(min-width:700px){.content-block{padding:68px 0}.content-split{grid-template-columns:minmax(0,1.3fr) minmax(300px,1fr);gap:65px}.info-grid,.tips-grid{grid-template-columns:repeat(3,minmax(0,1fr))}}
.theme-speed .hero{background:linear-gradient(150deg,#fffcf3,#fff1ce)}
.theme-speed .eyebrow{color:#895000}
.theme-speed .button{background:#855000}.theme-speed .button:hover{background:#6c4000}
.theme-speed .result{background:#fff5dc;border-color:#e4c983}.theme-speed .result-label{color:#704400}.theme-speed .result-extra{color:#5f4a2e}
.theme-speed .speed-time-hint{margin:2px 0 8px;font-weight:700}
.theme-speed .speed-distance-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
.theme-speed .speed-time-grid{grid-template-columns:repeat(3,minmax(0,1fr))}
.speed-links{padding:26px 0 30px;border-bottom:1px solid var(--line)}
.speed-links h2{font-size:1.16rem;letter-spacing:0;margin:0 0 14px}
.speed-links-grid{display:flex;gap:10px;overflow-x:auto;overscroll-behavior-inline:contain;padding:3px 3px 12px}
.speed-link{flex:0 0 146px;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:6px;padding:12px 8px;border:1px solid #e9d6a7;border-radius:12px;color:var(--navy);text-decoration:none;text-align:center;font-weight:700;font-size:.86rem;line-height:1.2}
.speed-link img{display:block;width:90px;height:66px;object-fit:contain}.speed-link-arrow{color:#895000}
.speed-link:hover,.speed-link[aria-current="page"]{border-color:#a76400;background:#fff6df}
.conversion-list{margin:16px 0 0;font-size:.9rem;color:#5f4a2e}.conversion-list>div{display:flex;justify-content:space-between;gap:16px;border-top:1px solid #e4c983;padding:7px 0}.conversion-list dt{font-weight:700}.conversion-list dd{margin:0;text-align:right;overflow-wrap:anywhere}
@media(min-width:700px){.speed-links{padding:30px 0 34px}.speed-links-grid{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));overflow:visible;padding-bottom:0}.speed-link{min-width:0;padding:14px}}

/* Area calculators: shared green theme and components. */
.theme-area .hero{background:linear-gradient(150deg,#f5fbf5,#e3f2e7)}
.theme-area .eyebrow{color:#326645}.theme-area a{color:#285e40}
.theme-area .button{background:#326645}.theme-area .button:hover{background:#244d33}
.theme-area .result{background:#edf8ee;border-color:#a9cdb2}.theme-area .result-label,.theme-area .result-extra{color:#305b41}
.theme-area .conversion-list{color:#305b41}.theme-area .conversion-list>div{border-color:#c7dfcd}
.area-shape-fields{border:0;padding:0;margin:0;min-width:0}
.area-shape-fields legend{font-size:.88rem;color:var(--muted);margin-bottom:12px;padding:0}
.area-square-option{display:flex;gap:10px;align-items:center;min-height:44px;margin-bottom:12px;font-size:.94rem;font-weight:650;cursor:pointer}
.area-square-option input{width:20px;height:20px;accent-color:#326645;flex-shrink:0}
.area-links{padding:26px 0 30px;border-bottom:1px solid var(--line)}
.area-links h2{font-size:1.16rem;letter-spacing:0;margin:0 0 14px}
.area-links-grid{display:flex;gap:10px;overflow-x:auto;overscroll-behavior-inline:contain;padding:3px 3px 12px}
.area-link{flex:0 0 146px;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:6px;padding:12px 8px;border:1px solid #bbd6c2;border-radius:12px;color:#305b41;text-decoration:none;text-align:center;font-weight:700;font-size:.86rem;line-height:1.2}
.area-link img{display:block;width:108px;height:70px;object-fit:contain}
.area-link:hover,.area-link[aria-current="page"]{border-color:#326645;background:#edf8ee}
.area-content-heading{margin-top:34px}.area-home-image{display:block;width:min(100%,280px);height:auto;margin-inline:auto}
@media(min-width:700px){.area-links{padding:30px 0 34px}.area-links-grid{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));overflow:visible;padding-bottom:0}.area-link{min-width:0;padding:14px}}