:root{font:100%/1.6 -apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color-scheme:light dark;--bg:#f5f5f7;--surface:#fff;--ink:#202522;--muted:#65706b;--line:#dfe4e1;--accent:#087d64;--accent-soft:#e9f4ef;--result:#f1f7f4;--header:rgba(245,245,247,.86);--danger:#b3261e;--radius:22px;--shadow:0 12px 40px #21352c06;--button-text:#fff;--button-hover:#06634f}*{box-sizing:border-box}html{-webkit-tap-highlight-color:transparent;-webkit-text-size-adjust:100%;scroll-padding-top:7rem}body{margin:0;background:var(--bg);color:var(--ink)}[hidden]{display:none!important}a{color:inherit;text-underline-offset:4px}button,input,select,textarea{font:inherit}button,a,summary{touch-action:manipulation}button,.mode-picker label{-webkit-user-select:none;user-select:none;-webkit-touch-callout:none}button{cursor:pointer}button:disabled{opacity:.45;cursor:not-allowed}a:active,summary:active{opacity:.7}button:active:not(:disabled),.button:active{transform:scale(.97)}:focus-visible{outline:3px solid var(--accent);outline-offset:4px}.wrap{width:min(1120px,100% - 64px);margin-inline:auto}.site-header{position:sticky;top:0;z-index:10;background:var(--header);backdrop-filter:blur(20px) saturate(150%);padding-top:env(safe-area-inset-top,0px)}.nav{height:78px;display:flex;align-items:center;justify-content:space-between;gap:24px}.brand{display:inline-flex;align-items:center;gap:10px;text-decoration:none;font-size:20px;font-weight:650;letter-spacing:-.7px;white-space:nowrap}.brand svg{width:26px;height:26px;color:var(--accent);fill:currentColor}.brand-light{font-weight:400}.nav-links{display:flex;gap:30px;font-size:14px}.nav-links a{text-decoration:none;color:var(--muted);padding-block:12px}.nav-links a[aria-current]{color:var(--ink);font-weight:600}.skip-link{position:fixed;top:-100px;left:20px;z-index:50;background:var(--surface);padding:12px}.skip-link:focus{top:10px}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}h1,h2,h3,p{margin-top:0}h1{font-size:clamp(2.25rem,4.5vw,3.6rem);line-height:1.08;letter-spacing:-.045em;font-weight:650;margin-bottom:20px}h2{font-size:26px;line-height:1.22;letter-spacing:-.025em;font-weight:600}h3{font-weight:600;letter-spacing:-.02em}p{color:var(--muted)}.home-hero{padding:92px 0 84px}.home-hero h1{font-size:clamp(2.8rem,5.8vw,4.5rem);max-width:850px}.home-hero h1 span{color:var(--muted)}.home-hero p{font-size:19px;margin:28px 0}.button{display:inline-flex;justify-content:center;align-items:center;gap:24px;min-height:48px;padding:12px 23px;border-radius:12px;font-size:14px;font-weight:600;text-decoration:none;border:1px solid transparent;transition:transform .12s ease-out,background-color .16s ease}.primary{background:var(--accent);color:var(--button-text)}.secondary{background:var(--surface);border-color:var(--line);color:var(--ink)}.section-heading{display:flex;align-items:end;justify-content:space-between;gap:24px;margin-bottom:28px}.section-heading h2{margin-bottom:8px}.section-heading p{margin:0}.text-link,.text-button{color:var(--accent);font-weight:600;font-size:14px}.text-link{text-decoration:none}.text-button{border:0;padding:10px 0;background:none;min-height:44px}.featured-tool{display:grid;grid-template-columns:1fr 1fr;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);text-decoration:none;overflow:hidden;box-shadow:var(--shadow)}.feature-copy{padding:48px}.category-label{font-size:11px;letter-spacing:.14em;font-weight:650;color:var(--accent)}.feature-copy h3{font-size:34px;line-height:1.15;margin:20px 0 16px;letter-spacing:-.035em}.feature-copy p{max-width:330px;font-size:16px}.feature-art{display:flex;align-items:center;background:var(--accent-soft);color:var(--accent);padding:30px}.feature-art svg{width:100%;height:auto}.principles{display:grid;grid-template-columns:repeat(3,1fr);gap:54px;padding:76px 0}.principles h3{font-size:18px;margin-bottom:10px}.principles p{font-size:14px;line-height:1.8}.site-footer{display:flex;align-items:center;gap:36px;padding-block:30px calc(30px + env(safe-area-inset-bottom,0px));border-top:1px solid var(--line);font-size:13px}.site-footer .brand{font-size:17px}.site-footer .brand svg{width:22px}.site-footer p{margin:0}.site-footer>a:last-child{margin-left:auto;color:var(--muted)}.breadcrumbs{display:flex;align-items:center;gap:12px;font-size:12px;color:var(--muted);padding:28px 0 32px;flex-wrap:wrap}.breadcrumbs a{text-decoration:none}.page-heading{padding-bottom:34px}.page-heading p{font-size:17px;margin-bottom:0}.mobile-break{display:none}.calculator-shell{display:grid;grid-template-columns:1fr 1fr;border:1px solid var(--line);background:var(--surface);border-radius:var(--radius);overflow:hidden;box-shadow:var(--shadow)}.input-panel,.result-panel{padding:32px}.result-panel{background:var(--result);border-left:1px solid var(--line)}.panel-heading{display:flex;justify-content:space-between;align-items:center;gap:14px;margin-bottom:26px}.panel-heading h2{font-size:18px;letter-spacing:-.02em;margin:0}.live-label,.result-status{font-size:11px;color:var(--muted);white-space:nowrap}.result-status{color:var(--accent)}.mode-picker{display:flex;border:0;border-radius:10px;padding:4px;background:var(--bg);margin:0 0 30px;gap:3px;min-width:0}.mode-picker label{flex:1;position:relative;text-align:center;cursor:pointer;min-width:0}.mode-picker input{position:absolute;opacity:0;width:1px;height:1px}.mode-picker span{display:block;padding:11px 4px;font-size:13px;font-weight:550;border-radius:7px;transition:background-color .16s,color .16s;white-space:nowrap}.mode-picker input:checked+span{background:var(--surface);box-shadow:0 2px 6px #0000000c}.mode-picker input:focus-visible+span{outline:3px solid var(--accent);outline-offset:2px}.unit-row{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:24px}.unit-row label{font-size:13px;color:var(--muted)}select{border:1px solid var(--line);background:var(--surface);color:var(--ink);padding:9px;border-radius:8px;max-width:58%;min-height:44px;font-size:16px}.dimension-fields{display:grid;grid-template-columns:1fr 1fr;gap:18px}.field label{display:block;font-size:14px;font-weight:600;margin-bottom:9px}.field label>span{display:block;font-size:11px;font-weight:400;color:var(--muted);margin-top:1px}.input-wrap{display:flex;align-items:center;background:var(--surface);border:1px solid var(--line);border-radius:11px;overflow:hidden;min-width:0}.input-wrap:focus-within{border-color:var(--accent);box-shadow:0 0 0 3px color-mix(in srgb,var(--accent) 13%,transparent)}.input-wrap input{border:0;outline:none;padding:13px 14px;font-size:25px;font-weight:500;color:var(--ink);width:100%;min-width:0;background:transparent;font-variant-numeric:tabular-nums}.input-wrap>span{padding-right:14px;color:var(--muted);font-size:14px}.input-wrap:has([aria-invalid=true]){border-color:var(--danger)}.error{color:var(--danger);font-size:12px;margin:7px 0 0;overflow-wrap:anywhere}.error:empty{display:none}.field-help{font-size:12px;line-height:1.8;margin:20px 0 0}.field-help a{color:var(--accent);white-space:nowrap}.form-bottom{display:flex;flex-wrap:wrap;gap:8px;margin-top:28px}.quiet-button{border:1px solid var(--line);color:var(--ink);background:transparent;border-radius:8px;padding:9px 15px;font-size:12px;min-height:44px;transition:transform .12s ease-out}.form-bottom p{font-size:11px;width:100%;margin:9px 0 0}.main-result{font-size:68px;line-height:1;letter-spacing:-.055em;font-weight:600;font-variant-numeric:tabular-nums;overflow-wrap:anywhere}.result-denominator{font-size:42px;color:var(--muted);font-weight:400;margin-left:5px}.result-caption{font-size:12px;margin:12px 0 24px}.secondary-results{display:grid;grid-template-columns:1fr 1fr;gap:24px}.secondary-results>div{display:flex;flex-direction:column}.secondary-results span{font-size:12px;color:var(--muted)}.secondary-results strong{font-size:25px;font-weight:550;letter-spacing:-.02em;overflow-wrap:anywhere}.diagram{margin:18px -4px 22px;text-align:center;color:var(--accent)}.diagram svg{display:block;width:100%;height:auto;max-height:235px}.diagram text{font-family:inherit;font-size:12px;fill:currentColor}.diagram>span{font-size:10px;color:var(--muted)}.result-actions{display:flex;gap:10px}.result-actions .primary{flex:1}.result-actions .secondary{min-width:100px}.empty-result{padding:20px 0;min-height:160px}.safety-note{font-size:11px;text-align:center;margin:18px 0 42px}.section-nav{display:flex;gap:30px;flex-wrap:wrap;border-block:1px solid var(--line);padding:18px 0;font-size:13px}.section-nav a{text-decoration:none}.guide-layout{display:grid;grid-template-columns:minmax(0,1fr) 310px;gap:90px;padding:60px 0}.guide-content section{margin-bottom:52px;scroll-margin-top:7rem}.guide-content p,.guide-content dd{font-size:14px;line-height:1.9}.definitions{margin-top:26px}.definitions>div{display:grid;grid-template-columns:65px 1fr;gap:20px;border-top:1px solid var(--line);padding:15px 0}.definitions dt{font-size:14px;font-weight:600}.definitions dd{margin:0;color:var(--muted)}#pitch-chart{align-self:start;padding:26px;background:var(--surface);border-radius:16px;border:1px solid var(--line)}#pitch-chart h2{font-size:21px}#pitch-chart p{font-size:12px}table{width:100%;border-collapse:collapse;font-size:13px;font-variant-numeric:tabular-nums;text-align:right}th:first-child,td:first-child{text-align:left}thead{color:var(--muted);font-size:11px}td,th{padding:13px 3px;border-bottom:1px solid var(--line)}th{font-weight:500}#pitch-chart .muted{margin:18px 0 0;font-size:11px}.example-block{display:flex;gap:22px;margin-top:25px}.example-number{font-size:12px;color:var(--accent);font-weight:650;padding-top:3px}.example-block h3{font-size:16px;margin-bottom:8px}.example-block p{margin-bottom:2px}.formula-list{padding:7px 22px;background:var(--surface);border:1px solid var(--line);border-radius:12px;margin:22px 0}.formula-list p{display:flex;justify-content:space-between;gap:12px;padding:13px 0;margin:0;border-bottom:1px solid var(--line);font-size:12px}.formula-list p:last-child{border:0}code{font-size:12px;color:var(--ink)}details{border-bottom:1px solid var(--line);padding:17px 0}summary{font-size:14px;font-weight:550;cursor:pointer;min-height:30px}details p{padding-top:14px;margin:0}.method-note h2{font-size:18px}.method-note p{font-size:12px}.muted{color:var(--muted)}.directory-page .page-heading{padding:20px 0 70px}.tool-row{display:flex;align-items:center;gap:28px;padding:28px;background:var(--surface);border:1px solid var(--line);border-radius:16px;text-decoration:none}.tool-symbol{display:grid;place-items:center;width:72px;height:72px;border-radius:16px;background:var(--accent-soft);color:var(--accent);font-size:40px;flex-shrink:0}.tool-row h3{margin:0 0 5px}.tool-row p{font-size:14px;margin:0 0 8px}.tool-row .muted{font-size:11px}.row-arrow{margin-left:auto;font-size:24px}.directory-note{padding:80px 0;max-width:600px}.directory-note h2{font-size:23px}.directory-note p{font-size:15px}#copy-status{font-size:12px;margin:10px 0 0}#copy-status:empty{display:none}#copy-fallback{margin-top:16px}#copy-fallback label{font-size:12px}textarea{width:100%;border:1px solid var(--line);background:var(--surface);color:var(--ink);border-radius:8px;padding:10px;font-size:16px}.print-input{display:none}.notice{padding:20px;border:1px solid var(--danger)}
@media(hover:hover) and (pointer:fine){.nav-links a:hover,.text-link:hover,.section-nav a:hover{color:var(--accent)}.primary:hover{background:var(--button-hover)}.secondary:hover,.quiet-button:hover{background:var(--accent-soft)}.tool-row:hover,.featured-tool:hover{border-color:var(--accent)}summary:hover{color:var(--accent)}}
:root[data-theme="dark"]{--bg:#141416;--surface:#202324;--ink:#f0f3f1;--muted:#a4b0aa;--line:#39413d;--accent:#55c9a5;--accent-soft:#1e3830;--result:#1b2b25;--header:rgba(20,20,22,.9);--danger:#ffb4a9;--button-text:#10251c;--button-hover:#7adbbc}
@media(prefers-color-scheme:dark){:root:not([data-theme]){--bg:#141416;--surface:#202324;--ink:#f0f3f1;--muted:#a4b0aa;--line:#39413d;--accent:#55c9a5;--accent-soft:#1e3830;--result:#1b2b25;--header:rgba(20,20,22,.9);--danger:#ffb4a9;--button-text:#10251c;--button-hover:#7adbbc}}
@media(max-width:850px){.guide-layout{grid-template-columns:minmax(0,1fr) 270px;gap:36px}.input-panel,.result-panel{padding:24px}.live-label{display:none}.feature-copy{padding:32px}.principles{gap:28px}.feature-art{padding:10px}}
@media(max-width:650px){.wrap{width:auto;margin-left:max(20px,env(safe-area-inset-left,0px));margin-right:max(20px,env(safe-area-inset-right,0px))}.nav{height:68px;gap:14px}.brand{font-size:18px;gap:7px}.brand svg{width:23px}.nav-links{gap:16px;font-size:12px}.nav-links a:first-child{display:none}.home-hero{padding:64px 0 54px}.home-hero h1{font-size:clamp(2.5rem,9vw,3.3rem)}.home-hero p{font-size:16px}.desktop-break{display:none}.section-heading{align-items:start;flex-direction:column;gap:12px}.section-heading h2{font-size:24px}.featured-tool{grid-template-columns:1fr}.feature-copy{padding:30px}.feature-copy h3{font-size:32px}.feature-art{padding:0 20px}.feature-art svg{max-height:240px}.principles{grid-template-columns:1fr;gap:22px;padding:45px 0}.principles p{margin-bottom:0}.site-footer{flex-wrap:wrap;gap:16px;font-size:11px}.site-footer p{order:3;width:100%}.site-footer>a:last-child{margin-left:auto}.breadcrumbs{padding:20px 0 24px;font-size:11px;gap:8px}.page-heading{padding-bottom:26px}.page-heading h1{font-size:34px}.page-heading p{font-size:14px}.mobile-break{display:initial}.calculator-shell{grid-template-columns:1fr;border-radius:18px}.input-panel,.result-panel{padding:24px 20px}.result-panel{border-left:0;border-top:1px solid var(--line)}.panel-heading{margin-bottom:20px}.panel-heading h2{font-size:17px}.mode-picker{margin-bottom:24px}.mode-picker span{font-size:12px}.dimension-fields{gap:12px}.input-wrap input{font-size:24px;padding:12px}.unit-row{margin-bottom:20px}.unit-row label{font-size:12px}.main-result{font-size:60px}.result-denominator{font-size:38px}.diagram svg{max-height:215px}.safety-note{text-align:left;font-size:11px;margin:16px 0 28px}.section-nav{gap:12px 24px;font-size:12px}.guide-layout{display:flex;flex-direction:column;gap:0;padding:36px 0}.guide-content{display:contents}.guide-content section{margin-bottom:38px}.guide-content h2{font-size:24px}#pitch-chart{order:0;width:100%;margin-bottom:38px}#rise-run{order:-2}#examples{order:-1}#formulas{order:1}#faq{order:2}#method{order:3}.formula-list{padding:5px 14px}.formula-list p{font-size:11px}.formula-list code{font-size:11px}.directory-page .page-heading{padding:10px 0 40px}.tool-row{padding:22px;gap:16px;align-items:start}.tool-symbol{width:45px;height:45px;font-size:28px;border-radius:10px}.tool-row h3{font-size:17px}.tool-row p{font-size:13px}.row-arrow{display:none}.directory-note{padding:50px 0}}
@media(prefers-reduced-motion:no-preference){.page-heading,.home-hero{animation:arrive .45s ease-out both}.calculator-shell,.featured-tool{animation:arrive .55s .06s ease-out both}@keyframes arrive{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important;scroll-behavior:auto!important}button:active,.button:active{transform:none}}
@media(prefers-reduced-transparency:reduce){.site-header{background:var(--bg);backdrop-filter:none}}
@media(prefers-contrast:more){:root,:root[data-theme]{--muted:var(--ink)}.site-header{background:var(--bg);backdrop-filter:none;border-bottom:1px solid var(--ink)}}
@media print{body{background:white;color:black}.site-header,.site-footer,.breadcrumbs,.page-heading p,.input-panel,.section-nav,.guide-layout,.result-actions,.safety-note,#copy-status,#copy-fallback{display:none!important}.wrap{width:100%;margin:0}.page-heading{padding:0}h1{font-size:25pt}.calculator-shell{display:block;border:1px solid #aaa;box-shadow:none}.result-panel{background:white;color:black;border:0}.result-panel p,.result-panel span{color:black}.result-panel .diagram{color:#111}.print-input{display:block}.main-result{font-size:45pt}body[data-valid=false] .calculator-shell{display:none!important}}
.input-panel,.result-panel{min-width:0}
@media(max-width:360px){.input-wrap input{font-size:20px;padding:12px 9px}.input-wrap>span{padding-right:9px;font-size:12px}.unit-row{display:grid;gap:8px}.unit-row select{max-width:100%;width:100%}.mode-picker span{font-size:11px}.result-actions{gap:8px}.result-actions .button{padding-inline:13px}.result-actions .secondary{min-width:72px}}

/* Appearance control: anchored, keyboard accessible, 44px touch target. */
.nav-links{align-items:center}
.theme-picker{position:relative;flex-shrink:0}
.theme-toggle{width:44px;height:44px;display:grid;place-items:center;padding:10px;border:1px solid var(--line);border-radius:50%;color:var(--ink);background:var(--surface);transition:transform .12s ease-out}
.theme-toggle svg{width:20px;height:20px;fill:none;stroke:currentColor;stroke-width:1.5}
.theme-panel{position:absolute;right:0;top:calc(100% + 10px);width:180px;padding:8px;background:var(--surface);border:1px solid var(--line);border-radius:14px;box-shadow:0 8px 30px #0002}
.theme-heading{display:block;color:var(--muted);font-size:11px;font-weight:600;letter-spacing:.04em;padding:8px 12px}
.theme-panel button{display:flex;align-items:center;justify-content:space-between;width:100%;min-height:44px;border:0;border-radius:8px;padding:10px 12px;background:transparent;color:var(--ink);font-size:14px;text-align:left}
.theme-panel button[aria-pressed="true"]{background:var(--accent-soft);color:var(--accent);font-weight:600}
.theme-panel button[aria-pressed="true"]::after{content:'✓'}
@media(hover:hover) and (pointer:fine){.theme-toggle:hover,.theme-panel button:hover{background:var(--accent-soft)}}
@media(max-width:650px){.nav-links{gap:10px}}
@media(max-width:360px){.nav{gap:8px}.nav-links{gap:6px}.brand{font-size:16px}.brand svg{width:20px}}
@media(prefers-reduced-motion:no-preference){.theme-panel{animation:theme-arrive .14s ease-out;transform-origin:top right}@keyframes theme-arrive{from{opacity:0;transform:translateY(-3px) scale(.98)}to{opacity:1;transform:none}}}

.tool-directory .featured-tool + .featured-tool{margin-top:24px}

.home-actions{display:flex;flex-wrap:wrap;gap:12px}.nav-links{align-items:center}
@media(max-width:700px){.nav-links{gap:12px}.nav-links>a[href="/calculators/"]{display:none}}
/* Tool-level language switch must remain available at narrow widths. */
.nav-links .language-link{white-space:nowrap;font-size:12px;min-height:44px;display:inline-flex;align-items:center}
@media(max-width:650px){.nav-links:has(.language-link)>a:not(.language-link){display:none}.nav-links:has(.language-link){gap:10px}}
:lang(zh-CN) h1,:lang(zh-CN) h2,:lang(zh-CN) h3{letter-spacing:0;line-height:1.3}