:root{--brand: #7c3aed;--brand-dark: #6d28d9;--brand-light: #f5f3ff;--brand-pale: #ede9fe;--brand-border: #c4b5fd;--navy: #1e1b4b;--color-bg: #f8fafc;--color-surface: #ffffff;--color-surface-hover: #f5f3ff;--color-border: #e5e7eb;--color-text: #111827;--color-text-muted: #6b7280;--color-text-subtle: #9ca3af;--color-success: #16a34a;--color-error: #dc2626;--color-warning-bg: #fefce8;--color-warning-border: #fbbf24;--color-warning-text: #92400e;--shadow-sm: 0 1px 2px 0 rgb(0 0 0 / .05);--shadow-md: 0 4px 6px -1px rgb(0 0 0 / .07), 0 2px 4px -2px rgb(0 0 0 / .05);--radius-sm: 6px;--radius-md: 10px;--radius-lg: 14px;--header-height: 56px}*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}html{-webkit-font-smoothing:antialiased}body{background:var(--color-bg);color:var(--color-text);font-family:Inter,system-ui,-apple-system,sans-serif;font-size:15px;line-height:1.6;min-height:100dvh}a{color:var(--brand);text-decoration:none}a:hover{text-decoration:underline}button{cursor:pointer;font:inherit;border:none;background:none}h1,h2,h3{line-height:1.3;color:var(--navy)}@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}}.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}.skip-link{position:absolute;left:8px;top:8px;z-index:999;padding:8px 16px;background:var(--brand);color:#fff;border-radius:var(--radius-sm);font-weight:600;font-size:14px;transform:translateY(-200%);transition:transform .2s;text-decoration:none}.skip-link:focus{transform:translateY(0)}.site-header{position:sticky;top:0;z-index:100;background:var(--color-surface);border-bottom:1px solid var(--color-border);box-shadow:var(--shadow-sm)}.site-header-inner{max-width:1120px;margin:0 auto;padding:0 20px;height:var(--header-height);display:flex;align-items:center;gap:16px}.header-lockup{display:flex;align-items:center;flex-shrink:0}.logo-useful-link{display:flex;align-items:center;gap:10px;text-decoration:none;color:inherit}.logo-useful-link:hover{text-decoration:none}.logo-useful-link:focus-visible{outline:2px solid var(--brand);outline-offset:2px;border-radius:2px}.logo-mark{display:block;flex-shrink:0}.logo-useful{font-weight:800;font-size:16px;letter-spacing:-.3px;color:#111827}.logo-sep{font-size:15px;font-weight:300;color:#9ca3af;margin:0 3px;pointer-events:none;-webkit-user-select:none;user-select:none}.logo-dates-link{display:flex;align-items:center;text-decoration:none;color:inherit}.logo-dates-link:hover{text-decoration:none}.logo-dates-link:focus-visible{outline:2px solid var(--brand);outline-offset:2px;border-radius:2px}.logo-product{font-weight:500;font-size:15px;letter-spacing:-.1px;color:#6b7280}.logo-dates-link--active .logo-product{color:var(--brand)}.header-nav{display:flex;align-items:center;gap:2px;flex:1}.nav-link{padding:6px 12px;border-radius:var(--radius-sm);font-size:14px;font-weight:500;color:var(--color-text-muted);text-decoration:none;transition:color .15s,background .15s;white-space:nowrap}.nav-link:hover{color:var(--brand);background:var(--brand-pale);text-decoration:none}.nav-link--active{color:var(--brand)!important;background:var(--brand-pale);font-weight:600}.nav-link:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.hamburger-btn{display:none;padding:8px;min-width:44px;min-height:44px;align-items:center;justify-content:center;border-radius:var(--radius-sm);color:var(--color-text-muted);margin-left:auto;font-size:20px;line-height:1}.hamburger-btn:hover{background:var(--brand-pale);color:var(--brand)}.hamburger-btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.mobile-menu{border-top:1px solid var(--color-border);background:var(--color-surface);padding:8px 16px 16px;display:flex;flex-direction:column;gap:2px}.mobile-nav-link{padding:12px 16px;border-radius:var(--radius-sm);font-size:15px;font-weight:500;color:var(--color-text);text-decoration:none;display:block;min-height:44px;display:flex;align-items:center}.mobile-nav-link:hover{background:var(--brand-pale);color:var(--brand);text-decoration:none}.mobile-nav-link--active{color:var(--brand);font-weight:600}.mobile-nav-link:focus-visible{outline:2px solid var(--brand);outline-offset:2px}@media(max-width:767px){.header-nav{display:none}.hamburger-btn{display:flex}}@media(max-width:320px){.site-header-inner{padding:0 12px}}.page-wrapper{min-height:100dvh;display:flex;flex-direction:column}main{flex:1;max-width:1120px;width:100%;margin:0 auto;padding:32px 20px 64px}@media(max-width:480px){main{padding:20px 16px 48px}}.page-title{font-size:clamp(22px,4vw,30px);font-weight:800;color:var(--navy);margin-bottom:8px}.page-subtitle{font-size:16px;color:var(--color-text-muted);margin-bottom:32px;max-width:540px;line-height:1.6}.calc-page-title{font-size:clamp(18px,3vw,24px);font-weight:800;color:var(--navy);margin-bottom:4px}.calc-page-subtitle{font-size:14px;color:var(--color-text-muted);margin-bottom:24px}.card{background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);box-shadow:var(--shadow-sm)}.card-body{padding:24px}@media(max-width:480px){.card-body{padding:16px}}.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;padding:9px 18px;border-radius:var(--radius-sm);font-weight:600;font-size:14px;min-height:44px;transition:background .15s,border-color .15s,color .15s;border:1px solid transparent;white-space:nowrap;cursor:pointer;text-decoration:none}.btn:hover{text-decoration:none}.btn:disabled{opacity:.5;cursor:default}.btn--primary{background:var(--brand);color:#fff;border-color:var(--brand)}.btn--primary:hover:not(:disabled){background:var(--brand-dark);border-color:var(--brand-dark)}.btn--ghost{background:var(--color-surface);color:var(--color-text);border-color:var(--color-border)}.btn--ghost:hover:not(:disabled){background:var(--brand-pale);border-color:var(--brand-border);color:var(--brand)}.btn--sm{min-height:36px;padding:5px 12px;font-size:13px}.btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.copy-btn{display:inline-flex;align-items:center;gap:6px;padding:8px 16px;border-radius:var(--radius-sm);font-weight:600;font-size:14px;min-height:44px;border:1px solid var(--color-border);background:var(--color-surface);color:var(--color-text);cursor:pointer;transition:all .15s;white-space:nowrap}.copy-btn:hover{background:var(--brand-pale);border-color:var(--brand-border);color:var(--brand)}.copy-btn--success{background:#f0fdf4;border-color:#86efac;color:var(--color-success)}.copy-btn--error{background:#fef2f2;border-color:#fca5a5;color:var(--color-error)}.copy-btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.today-btn{padding:0 12px;min-height:44px;height:44px;border-radius:var(--radius-sm);border:1.5px solid var(--color-border);background:var(--color-surface);color:var(--brand);font-weight:600;font-size:13px;cursor:pointer;white-space:nowrap;transition:all .15s;flex-shrink:0}.today-btn:hover{background:var(--brand-pale);border-color:var(--brand-border)}.today-btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.date-field{display:flex;flex-direction:column;gap:6px}.field-label{font-weight:600;font-size:14px;color:var(--color-text)}.date-input-row{display:flex;gap:8px;align-items:stretch}.date-input{flex:1;min-width:0;padding:9px 12px;border-radius:var(--radius-sm);border:1.5px solid var(--color-border);background:var(--color-surface);font:inherit;font-size:15px;color:var(--color-text);min-height:44px;transition:border-color .15s,box-shadow .15s}.date-input:focus{outline:none;border-color:var(--brand);box-shadow:0 0 0 3px #7c3aed1f}.date-input--error{border-color:var(--color-error)!important}.field-error{font-size:13px;color:var(--color-error);margin-top:2px}.adj-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}@media(max-width:480px){.adj-grid{grid-template-columns:repeat(2,1fr)}}.adj-field{display:flex;flex-direction:column;gap:4px}.adj-label{font-size:12px;font-weight:700;color:var(--color-text-muted);text-transform:uppercase;letter-spacing:.04em}.adj-input{padding:8px 10px;border:1.5px solid var(--color-border);border-radius:var(--radius-sm);font:inherit;font-size:18px;font-weight:600;color:var(--color-text);background:var(--color-surface);min-height:52px;width:100%;text-align:center;transition:border-color .15s,box-shadow .15s;-moz-appearance:textfield}.adj-input::-webkit-inner-spin-button,.adj-input::-webkit-outer-spin-button{-webkit-appearance:none}.adj-input:focus{outline:none;border-color:var(--brand);box-shadow:0 0 0 3px #7c3aed1f}.adj-input--error{border-color:var(--color-error)!important}.adj-error{font-size:11px;color:var(--color-error);min-height:16px}.seg-fieldset{border:none;padding:0;margin:0}.seg-legend{font-weight:600;font-size:14px;color:var(--color-text);display:block;margin-bottom:8px}.seg-ctrl{display:inline-flex;border:1.5px solid var(--color-border);border-radius:var(--radius-md);overflow:hidden;background:var(--color-bg)}.seg-opt{display:flex;align-items:center;justify-content:center;padding:10px 24px;font-size:14px;font-weight:600;color:var(--color-text-muted);min-height:44px;-webkit-user-select:none;user-select:none;transition:background .15s,color .15s;cursor:pointer;position:relative}.seg-opt+.seg-opt{border-left:1.5px solid var(--color-border)}.seg-opt input[type=radio]{position:absolute;opacity:0;width:0;height:0;margin:0}.seg-opt--active{background:var(--brand);color:#fff}.seg-opt:not(.seg-opt--active):hover{background:var(--brand-pale);color:var(--brand)}.seg-opt input[type=radio]:focus-visible~.seg-opt-label-text,.seg-opt:has(input[type=radio]:focus-visible){outline:2px solid var(--brand);outline-offset:2px}.toggle-label{display:flex;align-items:center;gap:10px;cursor:pointer;font-size:14px;font-weight:500;padding:4px 0;-webkit-user-select:none;user-select:none}.toggle-label input[type=checkbox]{width:18px;height:18px;border-radius:4px;accent-color:var(--brand);cursor:pointer;flex-shrink:0}.toggle-label input[type=checkbox]:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.swap-row{display:flex;align-items:center;gap:12px}.swap-divider{flex:1;height:1px;background:var(--color-border)}.calc-layout{display:flex;flex-direction:column;gap:20px;max-width:620px;margin:0 auto}.form-section{display:flex;flex-direction:column;gap:16px}.form-row{display:flex;flex-direction:column;gap:6px}.result-panel{background:var(--color-surface);border:1.5px solid var(--brand-border);border-radius:var(--radius-lg);padding:24px;box-shadow:var(--shadow-md)}@media(max-width:480px){.result-panel{padding:16px}}.result-primary{font-size:clamp(28px,6vw,42px);font-weight:800;color:var(--brand);display:block;margin-bottom:6px;line-height:1.1}.result-date-range{font-size:15px;color:var(--color-text);margin-bottom:8px;line-height:1.7}.result-inclusion{font-size:13px;color:var(--color-text-muted);margin-bottom:12px}.result-divider{border:none;border-top:1px solid var(--color-border);margin:16px 0}.result-breakdown{display:flex;flex-direction:column;gap:10px;margin-bottom:16px}.breakdown-row{display:flex;justify-content:space-between;align-items:baseline;gap:8px}.breakdown-label{font-size:12px;font-weight:700;color:var(--color-text-muted);text-transform:uppercase;letter-spacing:.04em;flex-shrink:0}.breakdown-value{font-size:15px;color:var(--color-text);text-align:right}.result-date-full{font-size:clamp(18px,4vw,24px);font-weight:800;color:var(--navy);margin-bottom:4px;line-height:1.2}.result-weekday-label{font-size:14px;color:var(--brand);font-weight:600;margin-bottom:16px}.result-explanation{font-size:14px;color:var(--color-text-muted);line-height:1.6;margin-bottom:8px}.result-actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:16px;padding-top:16px;border-top:1px solid var(--color-border)}.warning-box{background:var(--color-warning-bg);border:1px solid var(--color-warning-border);border-radius:var(--radius-md);padding:12px 16px;font-size:14px;color:var(--color-warning-text);line-height:1.5;margin-bottom:12px}.warning-icon{margin-right:4px}.reversed-notice{background:var(--brand-pale);border:1px solid var(--brand-border);border-radius:var(--radius-md);padding:12px 16px;font-size:14px;color:var(--navy);line-height:1.5;margin-bottom:12px}.instructional{text-align:center;padding:28px 16px;color:var(--color-text-muted);font-size:15px}.more-container{position:relative;display:none}.more-btn{display:flex;align-items:center;gap:4px;padding:6px 12px;border-radius:var(--radius-sm);font-size:14px;font-weight:500;color:var(--color-text-muted);white-space:nowrap;border:none;background:none;cursor:pointer;min-height:36px;transition:color .15s,background .15s}.more-btn:hover{color:var(--brand);background:var(--brand-pale)}.more-btn--active{color:var(--brand)!important;font-weight:600}.more-btn:focus-visible{outline:2px solid var(--brand);outline-offset:2px}.more-dropdown{position:absolute;top:calc(100% + 4px);right:0;z-index:200;background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-md);box-shadow:var(--shadow-md);min-width:160px;padding:4px;display:flex;flex-direction:column;gap:2px}.more-link{display:block;padding:10px 14px;border-radius:var(--radius-sm);font-size:14px;font-weight:500;color:var(--color-text);text-decoration:none;transition:background .15s,color .15s;white-space:nowrap}.more-link:hover{background:var(--brand-pale);color:var(--brand);text-decoration:none}.more-link--active{color:var(--brand);font-weight:600}.more-link:focus-visible{outline:2px solid var(--brand);outline-offset:2px}@media(min-width:768px)and (max-width:1023px){.nav-overflow{display:none!important}.more-container{display:block}}@media(min-width:1024px){.nav-overflow{display:inline-flex}.more-container{display:none}}.dt-pair{display:grid;grid-template-columns:1fr 1fr;gap:12px;align-items:start}@media(max-width:480px){.dt-pair{grid-template-columns:1fr}}.policy-fieldset{border:1px solid var(--color-border);border-radius:var(--radius-md);padding:14px 16px;margin:0}.policy-legend{font-size:13px;font-weight:600;color:var(--color-text-muted);padding:0 4px;line-height:1.4}.policy-options{display:flex;gap:24px;margin-top:10px;flex-wrap:wrap}.policy-option{display:flex;align-items:center;gap:8px;font-size:14px;font-weight:500;cursor:pointer}.policy-option input[type=radio]{accent-color:var(--brand);width:16px;height:16px}.disclosure-note{font-size:12px;color:var(--color-text-muted);line-height:1.5;margin-top:12px;margin-bottom:0}.age-disclaimer{border-top:1px solid var(--color-border);padding-top:12px;margin-top:12px}.birthday-notice{background:var(--brand-pale);border:1px solid var(--brand-border);border-radius:var(--radius-md);padding:10px 14px;font-size:14px;font-weight:600;color:var(--navy);margin-bottom:12px}.breakdown-sub{font-size:13px;color:var(--color-text-muted)}.biz-count-input{max-width:160px}.hub-layout{max-width:960px}.hub-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin-top:24px}@media(max-width:767px){.hub-grid{grid-template-columns:repeat(2,1fr)}}@media(max-width:479px){.hub-grid{grid-template-columns:1fr}}.hub-card{display:block;padding:24px;background:var(--color-surface);border:1.5px solid var(--color-border);border-radius:var(--radius-lg);text-decoration:none;transition:border-color .15s,box-shadow .15s,transform .15s;box-shadow:var(--shadow-sm)}.hub-card:hover{border-color:var(--brand-border);box-shadow:var(--shadow-md);text-decoration:none;transform:translateY(-2px)}.hub-card:focus-visible{outline:2px solid var(--brand);outline-offset:3px}.hub-card-icon{width:40px;height:40px;background:var(--brand-pale);border-radius:var(--radius-md);display:flex;align-items:center;justify-content:center;margin-bottom:14px;color:var(--brand)}.hub-card-title{font-size:16px;font-weight:700;color:var(--color-text);margin-bottom:6px}.hub-card-desc{font-size:14px;color:var(--color-text-muted);line-height:1.5}.hub-card-arrow{margin-top:16px;font-size:13px;font-weight:600;color:var(--brand)}.not-found{max-width:480px;margin:64px auto;text-align:center;padding:0 20px}.not-found-code{font-size:72px;font-weight:900;color:var(--brand-pale);line-height:1;margin-bottom:16px}.not-found-title{font-size:22px;font-weight:700;color:var(--navy);margin-bottom:8px}.not-found-desc{color:var(--color-text-muted);margin-bottom:24px}.hub-how-it-works-link{margin-top:28px;font-size:14px;color:var(--color-text-muted);text-align:center}.hub-how-it-works-link a{color:var(--brand);font-weight:600}.site-footer{border-top:1px solid var(--color-border);background:var(--color-surface);padding:24px 20px 32px;margin-top:auto}.site-footer-inner{max-width:1120px;margin:0 auto;display:flex;flex-direction:column;gap:12px;align-items:center}.footer-nav{display:flex;flex-wrap:wrap;gap:6px 20px;justify-content:center;list-style:none}.footer-link{font-size:13px;color:var(--color-text-muted);text-decoration:none;font-weight:500;transition:color .15s}.footer-link:hover,.footer-link:focus-visible{color:var(--brand);text-decoration:none}.footer-copy{font-size:12px;color:var(--color-text-subtle)}.page-wrapper{display:flex;flex-direction:column;min-height:100dvh}.page-wrapper>main{flex:1}.hiw-layout{max-width:760px;margin:0 auto;padding:32px 20px 48px}.hiw-toc{background:var(--brand-light);border:1px solid var(--brand-border);border-radius:var(--radius-md);padding:16px 20px;margin:24px 0 36px}.hiw-toc-label{font-size:12px;font-weight:700;color:var(--brand);text-transform:uppercase;letter-spacing:.06em;margin-bottom:8px}.hiw-toc-list{margin:0;padding-left:20px;display:grid;grid-template-columns:1fr 1fr;gap:4px 16px}.hiw-toc-list li{font-size:13px}.hiw-toc-list a{color:var(--brand);text-decoration:none}.hiw-toc-list a:hover{text-decoration:underline}@media(max-width:520px){.hiw-toc-list{grid-template-columns:1fr}}.hiw-article{display:flex;flex-direction:column;gap:48px}.hiw-section h2{font-size:20px;font-weight:700;color:var(--navy);margin-bottom:12px;padding-bottom:8px;border-bottom:2px solid var(--brand-pale)}.hiw-section p{margin-bottom:12px;color:var(--color-text);line-height:1.7}.hiw-section p:last-child{margin-bottom:0}.hiw-rules,.hiw-list{margin:12px 0;padding-left:24px;display:flex;flex-direction:column;gap:6px}.hiw-rules li,.hiw-list li{line-height:1.6;color:var(--color-text)}.hiw-example{background:var(--color-bg);border-left:3px solid var(--brand);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:14px 16px;margin:14px 0;font-family:Inter,system-ui,sans-serif}.hiw-example p{font-size:14px;margin-bottom:6px;line-height:1.5;color:var(--color-text)}.hiw-example p:last-child{margin-bottom:0}.hiw-example-step{padding-left:16px;color:var(--color-text-muted)!important}.hiw-calc-links{margin-top:48px;padding:20px 24px;background:var(--brand-light);border:1px solid var(--brand-border);border-radius:var(--radius-md)}.hiw-calc-links h2{font-size:16px;font-weight:700;color:var(--navy);margin-bottom:12px}.hiw-calc-links ul{list-style:none;padding:0;margin:0;display:flex;flex-wrap:wrap;gap:8px 24px}.hiw-calc-links a{font-size:14px;font-weight:600;color:var(--brand);text-decoration:none}.hiw-calc-links a:hover{text-decoration:underline}