:root{--ink:#172f38;--muted:#587078;--paper:#f3f7f8;--white:#fff;--line:#d6e2e5;--marine:#12343d;--teal:#137974;--liquid:#75c8be;--soft:#e7f2f0;--focus:#006dcb;--error:#ffddd0;--radius:8px}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:20px}
body{margin:0;background:var(--paper);color:var(--ink);font-family:"Avenir Next",Avenir,"Segoe UI",Arial,sans-serif;font-size:16px;line-height:1.6}
button,input,select{font:inherit;color:inherit}
button,a,input,select,summary{-webkit-tap-highlight-color:transparent}
button{cursor:pointer}a{color:var(--teal);text-underline-offset:5px}a:hover{text-decoration-thickness:2px}
button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid var(--focus);outline-offset:4px}
[hidden]{display:none!important}h1,h2,h3,p{margin:0}h2{font-size:25px;line-height:1.3;font-weight:650;letter-spacing:-.5px}h3{font-size:19px;line-height:1.4;font-weight:650}
.skip-link{position:absolute;left:20px;top:-80px;z-index:20;padding:10px 18px;background:#fff}.skip-link:focus{top:12px}
.site-header{max-width:1280px;margin:0 auto;padding:26px 40px;display:flex;gap:25px;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:center;gap:12px;font-size:25px;font-weight:700;letter-spacing:-.8px;color:var(--ink);text-decoration:none}.brand svg{width:27px;height:37px;fill:none;stroke:var(--teal);stroke-width:2;stroke-linejoin:round;stroke-linecap:round}
.site-header nav{display:flex;align-items:center;gap:26px}.site-header nav a{color:var(--ink);text-decoration:none}.site-header nav a:hover{text-decoration:underline}.nav-test{padding:9px 15px;border:1px solid #acbec3;border-radius:var(--radius)}
.page{max-width:1200px;margin:0 auto;padding:45px 40px 0}.intro{display:flex;align-items:center;justify-content:space-between;gap:40px;padding-bottom:35px}.byline{color:var(--teal);margin-bottom:12px}h1{font-size:clamp(32px,3.8vw,48px);line-height:1.13;font-weight:650;letter-spacing:-1.7px}.intro-copy{margin-top:18px;max-width:610px;font-size:18px;color:var(--muted);line-height:1.6}.intro-aside{padding-left:35px;border-left:1px solid var(--line);flex-shrink:0}.version{display:inline-block;color:var(--teal);background:var(--soft);border:1px solid #c8e4df;border-radius:30px;padding:4px 12px;font-size:16px}.intro-aside p{color:var(--muted);margin-top:12px}
.calculator{display:grid;grid-template-columns:1fr 1.05fr;background:var(--white);border:1px solid var(--line);border-radius:12px;overflow:hidden}.input-panel{padding:30px 32px;border-right:1px solid var(--line)}.input-panel h2{margin-bottom:19px}.solute-tabs{display:flex;border-bottom:1px solid var(--line);gap:20px;margin-bottom:24px}.solute-tabs button{border:0;border-bottom:3px solid transparent;background:none;font-weight:600;padding:6px 2px 12px;min-width:64px;color:var(--muted)}.solute-tabs button[aria-pressed="true"]{color:var(--teal);border-color:var(--teal)}
.field{margin-bottom:18px}.field label{display:block;margin-bottom:7px;font-weight:600;font-size:16px}.optional,.unit-note{font-weight:400;color:var(--muted)}.unit-note{float:right}.field input,.field select{width:100%;background:#fff;border:1px solid #b5c8ce;border-radius:var(--radius);min-height:46px;padding:9px 12px;line-height:1.5;font-size:18px}.field input[aria-invalid="true"]{border-color:#bd522b;background:#fff9f6}.field-hint{font-size:16px;color:var(--muted);line-height:1.5;margin-top:7px}.value-unit{display:flex}.value-unit input{flex:1;min-width:0;border-radius:var(--radius) 0 0 var(--radius)}.value-unit select{width:118px;border-left:0;border-radius:0 var(--radius) var(--radius) 0;background:#f5f9fa}
.mode-fieldset{border:0;padding:0;margin:0 0 22px}.mode-fieldset legend{font-weight:600;padding:0;margin-bottom:9px}.mode-options{display:flex;flex-wrap:wrap;gap:10px 18px}.mode-options label{display:flex;gap:8px;align-items:center;cursor:pointer}.mode-options input{width:18px;height:18px;accent-color:var(--teal);margin:0}
.concentration-presets{display:flex;flex-wrap:wrap;gap:6px;margin-top:8px}.concentration-presets button{background:#f4f8f9;border:1px solid var(--line);border-radius:5px;color:var(--muted);padding:4px 11px;min-height:35px;min-width:35px}.concentration-presets button:hover{border-color:var(--teal);color:var(--teal)}
details{border-top:1px solid var(--line)}summary{cursor:pointer;font-weight:600;padding:13px 0;list-style-position:outside;margin-left:19px}details[open] summary{margin-bottom:3px}.density-options .field-hint{margin:8px 0 14px}.check-label{display:flex;gap:10px;align-items:flex-start;margin-bottom:14px}.check-label input{width:18px;height:18px;accent-color:var(--teal);margin-top:5px;flex-shrink:0}.density-fields{display:grid;grid-template-columns:1fr 1fr;gap:14px}.density-fields .field{margin-bottom:0}.density-fields .unit-note{float:none;display:block;font-size:16px}
.form-footer{display:flex;justify-content:space-between;flex-wrap:wrap;align-items:center;gap:8px;margin-top:17px}.form-footer p{font-size:16px;color:var(--muted)}.subtle-button{background:none;border:0;border-bottom:1px solid currentColor;color:var(--teal);padding:3px 0;font-size:16px;line-height:1.5}
.output-panel{min-width:0}.result-surface{position:relative;background:var(--marine);color:#f3fbfc;padding:28px 32px 30px;min-height:357px;overflow:hidden}.result-topline{display:flex;justify-content:space-between;align-items:center;gap:15px;color:#b3d8d8;font-size:16px;min-height:30px}.result-topline>span:first-child{max-width:65%;overflow-wrap:anywhere}.formula{font-family:Georgia,"Times New Roman",serif;font-size:22px;white-space:nowrap}.result-surface h2{font-weight:500;font-size:19px;letter-spacing:0;margin-top:21px;max-width:75%;position:relative;z-index:1}.primary{font-size:clamp(39px,4.8vw,62px);line-height:1.13;letter-spacing:-1.5px;font-weight:600;margin-top:12px;position:relative;z-index:1;overflow-wrap:anywhere}.secondary{font-size:19px;color:#9fcaca;position:relative;z-index:1;margin-top:4px}.volume-principle{margin-top:25px;position:relative;z-index:1;color:#d2e6e8;font-size:16px;line-height:1.5;max-width:65%}.volume-visual{position:absolute;right:12px;bottom:26px;width:170px;text-align:center;color:#a3cccc;opacity:.88}.volume-visual p{font-size:16px;max-width:160px;line-height:1.4;margin:0 auto}.flask{width:170px;height:140px;overflow:visible}.glass,.glass-detail{fill:none;stroke:#bedce0;stroke-width:2;stroke-linecap:round;stroke-linejoin:round}.glass-detail{opacity:.6}.liquid{fill:#5dbeb5;opacity:.28}.liquid-surface{stroke:#70c4ba;stroke-width:2;fill:none}.volume-mark{stroke:#bce9e4;stroke-width:2}.volume-guide{stroke:#90b8be;stroke-width:1;stroke-dasharray:3 3;fill:none}.flask text{font:italic 18px Georgia,serif;fill:#c7e7e6}.bubble{fill:#96d5ce;opacity:.65}.result-surface.updated .liquid{animation:liquid-arrive .5s ease-out}@keyframes liquid-arrive{from{transform:translateY(16px);opacity:.1}to{transform:translateY(0);opacity:.28}}.result-error{font-size:18px;margin-top:22px;max-width:95%;color:var(--error)}.result-surface.invalid .volume-visual{opacity:.18}
.recipe-panel{padding:28px 32px}.section-heading{display:flex;justify-content:space-between;align-items:center;gap:15px}.section-heading>span{color:var(--muted);font-size:16px;white-space:nowrap}.recipe-panel ol{margin:19px 0 22px;padding-left:23px}.recipe-panel li{padding-left:7px;margin-bottom:10px;color:#3c555f}.recipe-panel li::marker{color:var(--teal);font-weight:600}.recipe-actions{display:flex;flex-wrap:wrap;gap:10px}.primary-button,.secondary-button{border-radius:var(--radius);font-weight:600;padding:10px 15px;min-height:46px;font-size:16px}.primary-button{border:1px solid var(--teal);background:var(--teal);color:#fff}.primary-button:hover{background:#0e635f}.secondary-button{border:1px solid #b5c8ce;background:#fff;color:var(--ink)}.secondary-button:hover{background:var(--paper)}button:disabled{opacity:.45;cursor:not-allowed}.action-status{min-height:25px;font-size:16px;color:var(--teal);margin:10px 0 14px}.calculation-details dl{margin:4px 0 17px}.calculation-details dl>div{display:grid;grid-template-columns:1.25fr 1fr;gap:15px;padding:8px 0;border-bottom:1px solid #e9eff1;font-size:16px}.calculation-details dt{color:var(--muted)}.calculation-details dd{margin:0;text-align:right;overflow-wrap:anywhere}.calculation-details h3{margin:14px 0 7px}
.history-section{margin:33px 0;padding:25px 0;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}.history-section .section-heading{align-items:flex-start}.history-section .section-heading p{color:var(--muted);margin-top:7px}.history-empty{margin-top:19px;color:var(--muted)}.history-list{list-style:none;margin:15px 0 0;padding:0;max-height:330px;overflow:auto;scrollbar-width:thin;scrollbar-color:#a5bbc1 transparent}.history-list li{padding:15px 0;border-top:1px solid var(--line);display:flex;gap:25px;justify-content:space-between;align-items:center}.history-list h3{font-size:18px;overflow-wrap:anywhere}.history-list p{font-size:16px;color:var(--muted);margin-top:3px}.history-item-actions{display:flex;gap:18px;flex-shrink:0}.clear-confirmation{background:#e6eff1;display:flex;flex-wrap:wrap;gap:15px;align-items:center;padding:15px;margin-top:16px;border-radius:var(--radius)}
.how-it-works{display:grid;grid-template-columns:1fr 1.1fr;gap:75px;padding:17px 0 40px}.how-it-works h2{font-size:32px;letter-spacing:-1px;line-height:1.25}.how-it-works p{color:var(--muted);margin-top:14px;max-width:520px}.how-it-works strong{font-weight:600;color:var(--ink)}.method-notes h3:not(:first-child){margin-top:24px}
.access-section{border-top:1px solid var(--line);padding:31px 0 40px}.access-options{display:grid;grid-template-columns:repeat(3,1fr);gap:35px;margin-top:22px}.access-options>div:not(:last-child){padding-right:25px;border-right:1px solid var(--line)}.access-options p{color:var(--muted);margin:10px 0 13px;font-size:16px}.access-options a{font-weight:600}
.site-footer{display:flex;gap:20px;justify-content:space-between;align-items:center;flex-wrap:wrap;max-width:1280px;padding:23px 40px;margin:0 auto;border-top:1px solid var(--line);color:var(--muted);font-size:16px}.noscript{max-width:1120px;margin:20px auto;padding:20px}
@media(min-width:1250px){.primary{font-size:62px}}
@media(max-width:1000px){.site-header{padding:22px 25px}.site-header nav{gap:18px}.page{padding:34px 25px 0}.input-panel,.recipe-panel,.result-surface{padding-left:24px;padding-right:24px}.volume-visual{width:135px;right:5px;bottom:24px}.flask{width:135px;height:116px}.volume-visual p{max-width:120px}.volume-principle{max-width:64%}.how-it-works{gap:35px}.site-footer{padding:23px 25px}.intro-aside{padding-left:20px}.access-options{gap:23px}}
@media(max-width:790px){.site-header{flex-wrap:wrap;gap:17px}.site-header nav{gap:20px;flex-wrap:wrap;font-size:16px}.nav-test{padding:0!important;border:0}.intro-aside{display:none}.calculator{grid-template-columns:1fr}.input-panel{border-right:0;border-bottom:1px solid var(--line)}.intro-copy{max-width:550px}.intro{padding-bottom:27px}.result-surface{min-height:325px;padding-top:25px}.volume-visual{width:175px;right:15px;bottom:25px}.flask{width:175px;height:140px}.volume-visual p{max-width:160px}.primary{font-size:59px;max-width:75%}.result-surface h2{max-width:75%}.volume-principle{max-width:60%}.how-it-works{grid-template-columns:1fr;gap:28px;padding-bottom:28px}.how-it-works p{max-width:none}.how-it-works h2 br{display:none}.access-options{grid-template-columns:1fr;gap:24px}.access-options>div:not(:last-child){border-right:0;border-bottom:1px solid var(--line);padding:0 0 21px}.history-section .section-heading{flex-wrap:wrap}}
@media(max-width:450px){.site-header{padding:18px 20px}.brand{font-size:24px}.site-header nav{gap:11px 17px;line-height:1.5}.page{padding:26px 16px 0}.intro{padding-left:4px;padding-right:4px}h1{font-size:36px;letter-spacing:-1.1px}.intro-copy{font-size:17px}.input-panel,.recipe-panel,.result-surface{padding-left:20px;padding-right:20px}.value-unit select{width:112px}.solute-tabs{gap:19px}.mode-options{gap:10px 16px}.mode-options label{font-size:16px}.result-topline{gap:8px}.formula{font-size:21px}.primary{font-size:48px;max-width:100%}.volume-visual{width:112px;right:2px;bottom:28px}.flask{width:112px;height:101px}.volume-visual p{display:none}.result-surface{min-height:311px}.volume-principle{max-width:72%}.result-surface h2{max-width:100%}.history-list li{align-items:flex-start;flex-wrap:wrap;gap:9px}.history-item-actions{width:100%}.site-footer{padding:22px 20px;gap:9px}.site-footer p{width:100%}.section-heading{align-items:flex-start}.density-fields{grid-template-columns:1fr}.recipe-actions{gap:9px}.recipe-actions button{flex-grow:1}.history-section{margin-top:27px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{animation:none!important;transition:none!important}}