:root{--primary: hsl(177, 85%, 22%);--on-primary: hsl(0, 0%, 100%);--surface: hsl(0, 0%, 100%);--on-surface: hsl(0, 0%, 11%);--surface-variant: hsl(210, 22%, 96%);--on-surface-variant: hsl(210, 11%, 19%);--outline: hsl(210, 14%, 78%);--success: hsl(122, 61%, 23%);--on-success: hsl(0, 0%, 100%);--error: hsl(4, 68%, 42%);--on-error: hsl(0, 0%, 100%);--spacing-unit: 8px;--border-radius: 12px;--border-radius-sm: 8px;--content-width: 880px;--card-shadow: 0 1px 3px rgba(0,0,0,.1);--type-result: 2.2rem;--type-h1: 1.6rem;--type-h2: 1.3rem;--type-body: 1rem;--type-small: .9rem;--font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;--font-family-mono: ui-monospace, "SF Mono", Monaco, "Cascadia Code", "Roboto Mono", Consolas, "Courier New", monospace}[data-theme=dark]{--primary: hsl(176, 65%, 58%);--on-primary: hsl(177, 100%, 10%);--surface: hsl(217, 15%, 8%);--on-surface: hsl(210, 10%, 90%);--surface-variant: hsl(217, 13%, 12%);--on-surface-variant: hsl(210, 14%, 78%);--outline: hsl(210, 6%, 25%);--success: hsl(122, 39%, 49%);--on-success: hsl(217, 15%, 8%);--error: hsl(4, 100%, 64%);--on-error: hsl(217, 15%, 8%);--card-shadow: 0 1px 3px rgba(0,0,0,.3)}*{margin:0;padding:0;box-sizing:border-box}body{font-family:var(--font-family);font-size:var(--type-body);line-height:1.5;background-color:var(--surface);color:var(--on-surface);transition:background-color .3s ease,color .3s ease;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}.skip-link{position:absolute;top:-40px;left:6px;background:var(--primary);color:var(--on-primary);padding:8px;text-decoration:none;border-radius:var(--border-radius-sm);z-index:1000;font-weight:500}.skip-link:focus{top:6px}.app-bar{background:var(--surface);border-bottom:1px solid var(--outline);position:sticky;top:0;z-index:100;-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px)}.app-bar-content{width:100%;margin:0 auto;padding:0 calc(var(--spacing-unit) * 2);display:flex;align-items:center;justify-content:space-between;height:64px}.logo{font-size:var(--type-h2);font-weight:600;color:var(--primary);text-decoration:none;transition:opacity .2s ease;display:flex;align-items:center;gap:.5rem}.logo-icon{width:24px;height:24px;color:var(--primary)}.logo:hover{opacity:.8}.nav-menu{display:none;gap:calc(var(--spacing-unit) * 3);list-style:none}.nav-menu a{color:var(--on-surface-variant);text-decoration:none;padding:calc(var(--spacing-unit) * 1) calc(var(--spacing-unit) * 2);border-radius:var(--border-radius-sm);transition:background-color .2s ease;min-height:44px;display:flex;align-items:center}.nav-menu a:hover,.nav-menu a:focus{background-color:var(--surface-variant)}.header-actions{display:flex;align-items:center;gap:calc(var(--spacing-unit) * 2)}.search-box{position:relative;display:none}.search-input{background:var(--surface-variant);border:1px solid var(--outline);border-radius:calc(var(--border-radius) * 2);padding:calc(var(--spacing-unit) * 1.5) calc(var(--spacing-unit) * 2);color:var(--on-surface);width:240px;transition:border-color .2s ease;min-height:44px}.search-input:focus{outline:2px solid var(--primary);border-color:transparent}.search-results{position:absolute;top:100%;left:0;right:0;background:var(--surface);border:1px solid var(--outline);border-radius:var(--border-radius-sm);box-shadow:var(--card-shadow);z-index:1000;display:none}.search-result-item{padding:calc(var(--spacing-unit) * 2);border-bottom:1px solid var(--outline);cursor:pointer;transition:background-color .2s ease}.search-result-item:hover{background:var(--surface-variant)}.search-result-item:last-child{border-bottom:none}.theme-toggle{background:var(--surface-variant);border:1px solid var(--outline);color:var(--on-surface-variant);border-radius:50%;width:44px;height:44px;display:flex;align-items:center;justify-content:center;cursor:pointer;transition:all .2s ease;font-size:1.2rem}.theme-toggle:hover,.theme-toggle:focus{background:var(--primary);color:var(--on-primary);border-color:var(--primary)}.mobile-menu-toggle{display:block;background:none;border:none;color:var(--on-surface);cursor:pointer;padding:calc(var(--spacing-unit) * 1);border-radius:var(--border-radius-sm);min-height:44px;min-width:44px;font-size:1.2rem}.mobile-menu{display:none;position:fixed;top:64px;left:0;right:0;background:var(--surface);border-bottom:1px solid var(--outline);padding:calc(var(--spacing-unit) * 2);z-index:99}.mobile-menu.active{display:block}.mobile-menu-list{list-style:none}.mobile-menu-list li{margin-bottom:calc(var(--spacing-unit) * 1)}.mobile-menu-list a{display:block;padding:calc(var(--spacing-unit) * 2);text-decoration:none;color:var(--on-surface);border-radius:var(--border-radius-sm);transition:background-color .2s ease;min-height:44px}.mobile-menu-list a:hover,.mobile-menu-list a:focus{background:var(--surface-variant)}.main-content{max-width:var(--content-width);margin:0 auto;padding:calc(var(--spacing-unit) * 3) calc(var(--spacing-unit) * 2);min-height:calc(100vh - 64px)}.hero-section{text-align:center;margin-bottom:calc(var(--spacing-unit) * 6)}.hero-title{font-size:var(--type-h1);font-weight:600;margin-bottom:calc(var(--spacing-unit) * 2);color:var(--on-surface)}.hero-description{font-size:var(--type-body);color:var(--on-surface-variant);max-width:600px;margin:0 auto calc(var(--spacing-unit) * 3);line-height:1.6}.trust-badge{display:inline-flex;align-items:center;gap:calc(var(--spacing-unit) * 1);background:var(--surface-variant);border:1px solid var(--outline);border-radius:var(--border-radius);padding:calc(var(--spacing-unit) * 1.5) calc(var(--spacing-unit) * 2);font-size:var(--type-small);color:var(--on-surface-variant)}.categories-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:calc(var(--spacing-unit) * 3);margin-bottom:calc(var(--spacing-unit) * 6)}.category-card{background:var(--surface-variant);border:1px solid var(--outline);border-radius:var(--border-radius);padding:calc(var(--spacing-unit) * 3);transition:transform .2s ease,box-shadow .2s ease;text-decoration:none;color:inherit;display:block}.category-card:hover,.category-card:focus{transform:translateY(-2px);box-shadow:var(--card-shadow)}.category-icon{width:48px;height:48px;background:var(--primary);color:var(--on-primary);border-radius:var(--border-radius-sm);display:flex;align-items:center;justify-content:center;margin-bottom:calc(var(--spacing-unit) * 2);font-size:1.5rem}.category-title{font-size:var(--type-h2);font-weight:600;margin-bottom:calc(var(--spacing-unit) * 1);color:var(--on-surface)}.category-description{color:var(--on-surface-variant);font-size:var(--type-small);margin-bottom:calc(var(--spacing-unit) * 2);line-height:1.4}.category-tools{list-style:none}.category-tools li{padding:calc(var(--spacing-unit) * .5) 0;font-size:var(--type-small);color:var(--on-surface-variant)}.breadcrumbs{margin-bottom:calc(var(--spacing-unit) * 3);font-size:var(--type-small);color:var(--on-surface-variant)}.breadcrumbs a{color:var(--primary);text-decoration:none;transition:opacity .2s ease}.breadcrumbs a:hover{opacity:.8}.tool-header{margin-bottom:calc(var(--spacing-unit) * 4)}.tool-title{font-size:var(--type-h1);font-weight:600;margin-bottom:calc(var(--spacing-unit) * 2);color:var(--on-surface)}.tool-intro{color:var(--on-surface-variant);margin-bottom:calc(var(--spacing-unit) * 3);line-height:1.6;max-width:600px}.calculator-container{background:var(--surface-variant);border:1px solid var(--outline);border-radius:var(--border-radius);padding:calc(var(--spacing-unit) * 3);margin-bottom:calc(var(--spacing-unit) * 4)}.input-group{margin-bottom:calc(var(--spacing-unit) * 3)}.input-group:last-of-type{margin-bottom:calc(var(--spacing-unit) * 4)}.input-label{display:block;font-weight:500;margin-bottom:calc(var(--spacing-unit) * 1);color:var(--on-surface);font-size:var(--type-body)}.input-field{width:100%;background:var(--surface);border:2px solid var(--outline);border-radius:var(--border-radius-sm);padding:calc(var(--spacing-unit) * 2);font-size:var(--type-body);color:var(--on-surface);transition:border-color .2s ease,box-shadow .2s ease;min-height:44px;font-family:var(--font-family)}.input-field:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 2px var(--primary)}.input-field::-moz-placeholder{color:var(--on-surface-variant);opacity:.7}.input-field::placeholder{color:var(--on-surface-variant);opacity:.7}.result-section{background:var(--surface);border:2px solid var(--primary);border-radius:var(--border-radius);padding:calc(var(--spacing-unit) * 3);text-align:center;margin-bottom:calc(var(--spacing-unit) * 2)}.result-label{font-size:var(--type-small);color:var(--on-surface-variant);margin-bottom:calc(var(--spacing-unit) * 1);font-weight:500}.result-value{font-size:var(--type-result);font-weight:600;color:var(--primary);margin-bottom:calc(var(--spacing-unit) * 2);font-family:var(--font-family-mono);word-break:break-all}.copy-button{background:var(--primary);color:var(--on-primary);border:none;border-radius:var(--border-radius-sm);padding:calc(var(--spacing-unit) * 1.5) calc(var(--spacing-unit) * 3);font-size:var(--type-body);cursor:pointer;transition:opacity .2s ease,transform .1s ease;min-height:44px;font-weight:500}.copy-button:hover,.copy-button:focus{opacity:.9}.copy-button:active{transform:scale(.98)}.show-math{margin-top:calc(var(--spacing-unit) * 2)}.show-math-toggle{background:none;border:1px solid var(--outline);color:var(--on-surface-variant);border-radius:var(--border-radius-sm);padding:calc(var(--spacing-unit) * 1) calc(var(--spacing-unit) * 2);cursor:pointer;font-size:var(--type-small);min-height:44px;transition:background-color .2s ease;font-family:var(--font-family)}.show-math-toggle:hover,.show-math-toggle:focus{background:var(--surface-variant)}.math-explanation{background:var(--surface-variant);border-radius:var(--border-radius-sm);padding:calc(var(--spacing-unit) * 2);margin-top:calc(var(--spacing-unit) * 2);font-family:var(--font-family-mono);font-size:var(--type-small);color:var(--on-surface-variant);display:none;line-height:1.4}.math-explanation.visible{display:block;animation:fadeIn .2s ease}@keyframes fadeIn{0%{opacity:0;transform:translateY(-5px)}to{opacity:1;transform:translateY(0)}}.ad-placeholder{background:var(--surface-variant);border:1px solid var(--outline);border-radius:var(--border-radius-sm);padding:calc(var(--spacing-unit) * 2);text-align:center;color:var(--on-surface-variant);font-size:var(--type-small);margin:calc(var(--spacing-unit) * 4) 0;min-height:250px;display:flex;align-items:center;justify-content:center}.related-tools{margin:calc(var(--spacing-unit) * 4) 0}.related-tools h3{font-size:var(--type-h2);margin-bottom:calc(var(--spacing-unit) * 2);color:var(--on-surface)}.related-tools-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:calc(var(--spacing-unit) * 2)}.related-tool-link{background:var(--surface-variant);border:1px solid var(--outline);border-radius:var(--border-radius-sm);padding:calc(var(--spacing-unit) * 2);text-decoration:none;color:var(--on-surface);transition:background-color .2s ease,color .2s ease;display:block;min-height:44px;display:flex;align-items:center}.related-tool-link:hover,.related-tool-link:focus{background:var(--primary);color:var(--on-primary)}.faqs{margin:calc(var(--spacing-unit) * 4) 0}.faqs h3{font-size:var(--type-h2);margin-bottom:calc(var(--spacing-unit) * 3);color:var(--on-surface)}.faq-item{border-bottom:1px solid var(--outline);padding:calc(var(--spacing-unit) * 2) 0}.faq-question{font-weight:500;margin-bottom:calc(var(--spacing-unit) * 1);color:var(--on-surface);font-size:var(--type-body)}.faq-answer{color:var(--on-surface-variant);font-size:var(--type-small);line-height:1.5}.footer{background:var(--surface-variant);border-top:1px solid var(--outline);margin-top:calc(var(--spacing-unit) * 6);padding:calc(var(--spacing-unit) * 4) calc(var(--spacing-unit) * 2)}.footer-content{max-width:var(--content-width);margin:0 auto;display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:calc(var(--spacing-unit) * 4)}.footer-section h4{font-size:var(--type-body);font-weight:600;margin-bottom:calc(var(--spacing-unit) * 2);color:var(--on-surface)}.footer-links{list-style:none}.footer-links li{margin-bottom:calc(var(--spacing-unit) * 1)}.footer-links a{color:var(--on-surface-variant);text-decoration:none;font-size:var(--type-small);transition:color .2s ease;line-height:1.4}.footer-links a:hover,.footer-links a:focus{color:var(--primary)}.toast{position:fixed;bottom:calc(var(--spacing-unit) * 3);left:50%;transform:translate(-50%);background:var(--success);color:var(--on-success);padding:calc(var(--spacing-unit) * 2) calc(var(--spacing-unit) * 3);border-radius:var(--border-radius);z-index:1000;opacity:0;transition:opacity .3s ease;font-weight:500;box-shadow:var(--card-shadow)}.toast.visible{opacity:1}.hub-intro{text-align:center;margin-bottom:calc(var(--spacing-unit) * 4)}.hub-title{font-size:var(--type-h1);font-weight:600;margin-bottom:calc(var(--spacing-unit) * 2);color:var(--on-surface)}.hub-description{color:var(--on-surface-variant);max-width:600px;margin:0 auto;line-height:1.6}.tools-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:calc(var(--spacing-unit) * 3)}.tool-card{background:var(--surface-variant);border:1px solid var(--outline);border-radius:var(--border-radius);padding:calc(var(--spacing-unit) * 3);transition:transform .2s ease,box-shadow .2s ease;text-decoration:none;color:inherit;display:block}.tool-card:hover,.tool-card:focus{transform:translateY(-2px);box-shadow:var(--card-shadow)}.tool-card-title{font-size:var(--type-h2);font-weight:600;margin-bottom:calc(var(--spacing-unit) * 1);color:var(--on-surface)}.tool-card-description{color:var(--on-surface-variant);font-size:var(--type-small);line-height:1.4}.inputs-row{display:grid;grid-template-columns:1fr 1fr;gap:calc(var(--spacing-unit) * 2)}.inputs-row .input-group{margin-bottom:calc(var(--spacing-unit) * 2)}.epoch-inputs-row{display:grid;grid-template-columns:1fr auto 1fr;gap:calc(var(--spacing-unit) * 2);align-items:end}.conversion-arrow{display:flex;align-items:center;justify-content:center;padding-bottom:calc(var(--spacing-unit) * 3);color:var(--on-surface-variant);font-size:1.5rem;font-weight:700}.conversion-arrow svg{width:24px;height:24px}.date-input-right{text-align:right}@media (max-width: 768px){.epoch-inputs-row{grid-template-columns:1fr;gap:calc(var(--spacing-unit) * 2)}.epoch-inputs-row .input-group:first-child{order:1}.conversion-arrow{order:2;padding:calc(var(--spacing-unit) * 1) 0;font-size:2rem;font-weight:700}.epoch-inputs-row .input-group:last-child{order:3}.date-input-right{text-align:left}}.tool-title-container{display:flex;align-items:baseline;gap:calc(var(--spacing-unit) * 1.5)}.bookmark-button{background:var(--surface-variant);color:var(--on-surface);border:1px solid var(--outline);border-radius:var(--border-radius);padding:calc(var(--spacing-unit) * 1) calc(var(--spacing-unit) * 1.5);font-size:1.1rem;font-weight:500;cursor:pointer;transition:all .2s ease;flex-shrink:0;min-width:44px;height:44px;-webkit-user-select:none;-moz-user-select:none;user-select:none}.bookmark-button:hover{background:var(--primary);color:var(--on-primary);border-color:var(--primary)}.hero-section .bookmark-button{margin:calc(var(--spacing-unit) * 2) auto;display:block;text-align:center}@media (max-width: 768px){.tool-title-container{flex-direction:column;align-items:flex-start;gap:calc(var(--spacing-unit) * 1.5)}.bookmark-button{display:none}}@media (min-width: 768px){.nav-menu{display:flex}.search-box{display:block}.mobile-menu-toggle{display:none}.categories-grid{grid-template-columns:repeat(2,1fr)}.main-content{display:grid;grid-template-columns:1fr 160px;gap:calc(var(--spacing-unit) * 4)}.primary-content{grid-column:1}.sidebar{grid-column:2}.sidebar .ad-placeholder{margin:0;min-height:600px;position:sticky;top:calc(64px + var(--spacing-unit) * 2)}.inputs-row{grid-template-columns:1fr 1fr 1fr}}@media (min-width: 1024px){.categories-grid{grid-template-columns:repeat(3,1fr)}}@media (prefers-reduced-motion: reduce){*{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}}:focus{outline:2px solid var(--primary);outline-offset:2px}button:focus,input:focus,select:focus,textarea:focus{outline:2px solid var(--primary);outline-offset:2px}.error-message{color:var(--error);font-size:var(--type-small);margin-top:calc(var(--spacing-unit) * 1);display:none}.error-message.visible{display:block}.input-field.error{border-color:var(--error)}.loading{opacity:.6;pointer-events:none}.hidden{display:none}.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}.text-center{text-align:center}@media print{.app-bar,.footer,.ad-placeholder,.related-tools{display:none}.main-content{max-width:none;padding:0}.calculator-container{border:1px solid #000;background:#fff}}