/* Acids lesson. Shared navigation, typography variables and themes come from the site. */
.acids-page {
    --acids-acidic: #f28d87;
    --acids-neutral: #84d1aa;
    --acids-alkaline: #a7b1fa;
    --acids-hydroxide: #91c9f8;
    --acids-success: #84d1aa;
    --acids-error: #f28d87;
    line-height: 1.65;
    padding-top: 12px;
}
.acids-page [hidden] { display: none !important; }
.acids-page :is(button, input) { font: inherit; }
.acids-page :is(button, a, summary, input) { touch-action: manipulation; }
.acids-page :focus-visible { outline: 3px solid var(--color-accent); outline-offset: 5px; }
.acids-page :is(h1, h2, h3, h4) { color: var(--color-text); line-height: 1.2; }
.acids-page h2 { margin: 0; font-size: clamp(1.4rem, 2.7vw, 2rem); letter-spacing: -0.025em; }
.acids-page h3 { margin: 0 0 12px; }
.acids-page p { color: var(--color-text-muted); }
.acids-page a { color: var(--color-accent); text-underline-offset: 4px; }
.acids-page section[id], .acids-page details[id], #acidsMeasuring { scroll-margin-top: calc(var(--site-top-height, 64px) + 24px); }
.acids-eyebrow { margin: 0 0 12px; color: var(--color-accent) !important; font-size: 0.68rem; font-weight: 700; letter-spacing: 0.15em; }
.acids-small { font-size: 0.75rem; color: var(--color-text-muted); }
.acids-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 10px; }
.acids-button { display: inline-flex; align-items: center; justify-content: center; gap: 15px; min-height: 46px; padding: 10px 18px; border: 1px solid var(--color-border); border-radius: 9px; background: transparent; color: var(--color-text) !important; text-decoration: none; font-size: 0.85rem !important; font-weight: 700; cursor: pointer; }
.acids-button:hover { background: var(--color-bg-card); border-color: var(--color-accent); }
.acids-button-primary { background: var(--color-accent); border-color: var(--color-accent); color: #241507 !important; }
.acids-button-primary:hover { background: #f9bf7a; border-color: #f9bf7a; }
.acids-hero { display: grid; grid-template-columns: 1.4fr 1fr; align-items: center; gap: 40px; padding: 26px 0 48px; }
.acids-hero h1 { margin: 16px 0 20px; font-size: clamp(2.5rem, 4.6vw, 4rem); line-height: 1.04; letter-spacing: -0.055em; }
.acids-hero h1 > span { color: var(--color-accent); }
.acids-hero-copy > p:not(.acids-eyebrow) { max-width: 590px; margin-bottom: 26px; font-size: 0.95rem; }
.acids-hero-art { position: relative; display: flex; flex-direction: column; align-items: center; overflow: hidden; min-height: 290px; padding: 30px 24px 22px; border: 1px solid var(--color-border); border-radius: 20px; background: radial-gradient(ellipse at 50% 35%, rgba(70, 170, 131, 0.13), transparent 70%), var(--color-bg-panel); }
.acids-hero-kicker { position: relative; font-size: 0.6rem; letter-spacing: 0.17em; color: var(--color-text-muted); }
.acids-hero-number { position: relative; margin: 6px 0 0; color: var(--acids-neutral); font-size: 6.6rem; font-weight: 700; line-height: 1.2; letter-spacing: -0.08em; }
.acids-hero-number > span { margin-left: 12px; color: var(--color-text-muted); font-size: 1.15rem; letter-spacing: 0; }
.acids-hero-neutral { position: relative; font-size: 0.78rem; }
.acids-mini-scale { z-index: 1; display: flex; width: 100%; gap: 3px; margin-top: 26px; }
.acids-mini-scale > span { height: 22px; flex: 1; border-radius: 3px; background: var(--ph-colour); }
.acids-hero-endpoints { display: flex; justify-content: space-between; width: 100%; margin-top: 7px; font-size: 0.55rem; letter-spacing: 0.1em; color: var(--color-text-muted); }
.acids-panel { padding: clamp(20px, 3vw, 34px); border: 1px solid var(--color-border); border-radius: 18px; background: var(--color-bg-panel); box-shadow: var(--card-shadow); }
.acids-section-heading { display: flex; align-items: center; justify-content: space-between; gap: 20px; margin-bottom: 18px; }
.acids-section-heading .acids-eyebrow { margin-bottom: 9px; }
.acids-section-intro { max-width: 820px; margin: 0 0 26px; font-size: 0.9rem; }
.acids-explorer-layout { display: grid; grid-template-columns: minmax(0, 1.65fr) minmax(230px, 1fr); gap: 28px; }
.acids-scale-controls { min-width: 0; }
.acids-scale-zones { display: grid; grid-template-columns: repeat(15, minmax(0, 1fr)); align-items: start; gap: 3px; margin-bottom: 14px; font-size: 0.72rem; font-weight: 700; }
.acids-scale-direction { grid-column: span 7; color: var(--acids-kind-colour); }
.acids-scale-direction[data-kind="acidic"] { padding-right: 12px; }
.acids-scale-direction[data-kind="alkaline"] { padding-left: 12px; text-align: right; }
.acids-scale-neutral { display: flex; flex-direction: column; align-items: center; color: var(--acids-neutral); }
.acids-scale-neutral small { font-size: 0.65rem; font-weight: 400; white-space: nowrap; }
.acids-scale-arrow { position: relative; display: block; height: 12px; margin-top: 5px; }
.acids-scale-arrow::before { content: ""; position: absolute; inset: 50% 0 auto; height: 3px; border-radius: 2px; background: currentColor; transform: translateY(-50%); }
.acids-scale-arrow::after { content: ""; position: absolute; top: 50%; width: 0; height: 0; border-top: 6px solid transparent; border-bottom: 6px solid transparent; transform: translateY(-50%); }
.acids-scale-direction[data-kind="acidic"] .acids-scale-arrow::after { left: 0; border-right: 9px solid currentColor; }
.acids-scale-direction[data-kind="alkaline"] .acids-scale-arrow::after { right: 0; border-left: 9px solid currentColor; }
.acids-scale { display: grid; grid-template-columns: repeat(15, minmax(0, 1fr)); gap: 3px; padding: 5px 0 10px; }
.acids-scale-stop { min-width: 0; height: 64px; padding: 0; border: 2px solid transparent; border-radius: 5px; background: var(--ph-colour); color: #201a1a; font-size: 0.8rem !important; font-weight: 700 !important; cursor: pointer; transition: transform 150ms; }
.acids-scale-stop:hover { transform: translateY(-4px); }
.acids-scale-stop[aria-pressed="true"] { outline: 2px solid var(--color-text); outline-offset: 2px; transform: translateY(-4px); }
.acids-slider-label { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 6px; margin-top: 15px; font-weight: 700; font-size: 0.82rem; }
.acids-slider-label > span { font-weight: 400; font-size: 0.72rem; color: var(--color-text-muted); }
.acids-slider { width: 100%; min-height: 44px; margin: 3px 0 16px; accent-color: var(--color-accent); cursor: pointer; }
.acids-examples { display: flex; flex-wrap: wrap; gap: 8px; }
.acids-examples > button { display: flex; flex-direction: column; gap: 2px; min-height: 58px; flex: 1 1 95px; padding: 9px 12px; border: 1px solid var(--color-border); border-radius: 8px; background: transparent; color: var(--color-text); text-align: left; font-size: 0.76rem; cursor: pointer; }
.acids-examples small { color: var(--color-text-muted); font-size: 0.65rem; }
.acids-examples > button:hover, .acids-examples > button[aria-pressed="true"] { border-color: var(--color-accent); background: var(--color-bg-card); }
.acids-footnote { margin: 18px 0 0; font-size: 0.73rem; }
.acids-readout { display: flex; align-items: center; align-self: stretch; gap: 18px; min-width: 0; padding: 24px 18px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-card); }
.acids-readout-copy { flex: 1; min-width: 0; }
.acids-readout .acids-eyebrow { font-size: 0.6rem; }
.acids-reading { margin: 0 !important; color: var(--color-text) !important; font-size: 3.2rem; font-weight: 700; line-height: 1.25; letter-spacing: -0.05em; }
.acids-reading > span { color: var(--color-text-muted); font-size: 0.85rem; font-weight: 400; letter-spacing: 0; }
.acids-kind { display: inline-block; margin-top: 10px; color: var(--acids-kind-colour); font-size: 0.9rem; }
.acids-page [data-kind="acidic"] { --acids-kind-colour: var(--acids-acidic); }
.acids-page [data-kind="neutral"] { --acids-kind-colour: var(--acids-neutral); }
.acids-page [data-kind="alkaline"] { --acids-kind-colour: var(--acids-alkaline); }
#acidsPhDescription { margin-bottom: 0; font-size: 0.78rem; }
.acids-indicator-caption { margin-bottom: 0; font-size: 0.67rem; }
.acids-indicator { position: relative; align-self: center; flex-shrink: 0; width: 43px; height: 166px; border: 1px solid var(--color-border); border-top: 0; border-radius: 0 0 22px 22px; overflow: hidden; background: rgba(128, 128, 128, 0.04); }
.acids-indicator-liquid { position: absolute; inset: 62px 4px 4px; border-radius: 0 0 18px 18px; background: var(--indicator-colour); opacity: 0.6; }
.acids-indicator-paper { position: absolute; top: 8px; left: 14px; z-index: 1; width: 13px; height: 112px; border: 1px solid rgba(0, 0, 0, 0.16); border-radius: 2px; background: linear-gradient(to bottom, #eee5cd 48%, var(--indicator-colour) 48%); }
.acids-indicator-mark { position: absolute; top: 40px; right: 0; width: 10px; height: 80px; background: repeating-linear-gradient(to bottom, var(--color-border) 0 1px, transparent 1px 16px); }
.acids-lesson { margin: 46px 0; }
.acids-ion-legend { display: flex; flex-wrap: wrap; gap: 12px 28px; margin: -6px 0 24px; color: var(--color-text-muted); font-size: 0.8rem; }
.acids-ion-legend > span { display: inline-flex; align-items: center; gap: 9px; }
.acids-ion-key { display: inline-flex; align-items: center; justify-content: center; min-width: 34px; height: 34px; border: 1px solid currentColor; border-radius: 50%; font-size: 0.85rem; font-weight: 700; }
.acids-ion-key sup { align-self: flex-start; margin-top: 5px; font-size: 0.65em; }
.acids-ion-key-h { color: var(--acids-acidic); background: rgba(224, 91, 98, 0.1); }
.acids-ion-key-oh { color: var(--acids-hydroxide); background: rgba(72, 164, 201, 0.1); }
.acids-concept-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; }
.acids-concept { display: flex; flex-direction: column; min-width: 0; padding: 24px; border: 1px solid var(--color-border); border-top: 3px solid var(--acids-kind-colour); border-radius: 12px; background: var(--color-bg-panel); }
.acids-concept-heading { display: flex; align-items: baseline; justify-content: space-between; flex-wrap: wrap; gap: 8px; }
.acids-concept-range { color: var(--acids-kind-colour); font-size: 0.7rem; font-weight: 700; }
.acids-concept h3 { margin: 0; font-size: 1.35rem; }
.acids-concept p:not(.acids-ion-balance) { flex: 1; margin: 0 0 20px; font-size: 0.8rem; }
.acids-concept .acids-ion-balance { margin: 8px 0; color: var(--color-text); font-size: 1rem; font-weight: 700; }
.acids-concept strong { color: var(--acids-kind-colour); font-size: 0.75rem; }
.acids-beaker { display: block; width: 100%; max-width: 300px; height: auto; margin: 12px auto 0; overflow: visible; }
.acids-glass { fill: none; stroke: var(--color-text-muted); stroke-width: 2.5; stroke-linecap: round; stroke-linejoin: round; }
.acids-glass-shine { fill: none; stroke: var(--color-text-muted); stroke-width: 3; stroke-linecap: round; opacity: 0.15; }
.acids-glass-shadow { fill: var(--color-text-muted); opacity: 0.09; }
.acids-glass-ticks { fill: none; stroke: var(--color-text-muted); stroke-width: 1.5; opacity: 0.4; }
.acids-solution { fill: var(--acids-hydroxide); fill-opacity: 0.09; }
.acids-waterline { fill: none; stroke: var(--acids-hydroxide); stroke-width: 1.5; opacity: 0.4; }
.acids-particle-h { --particle-colour: var(--acids-acidic); }
.acids-particle-oh { --particle-colour: var(--acids-hydroxide); }
.acids-particle-a { --particle-colour: var(--acids-neutral); }
.acids-particle-ha { --particle-colour: var(--color-text-muted); }
.acids-particle :is(circle, rect) { fill: var(--particle-colour); fill-opacity: 0.12; stroke: var(--particle-colour); stroke-width: 1.5; }
.acids-particle text { fill: var(--particle-colour); text-anchor: middle; dominant-baseline: middle; font: 700 14px Arial, sans-serif; }
.acids-beaker { --beaker-glass: #d1c0af; --beaker-surface: #7ba6b3; --beaker-liquid-top: #203842; --beaker-liquid-bottom: #2b4d5b; }
.acids-beaker .acids-glass { stroke: var(--beaker-glass); stroke-width: 2.5; }
.acids-beaker .acids-waterline { stroke: var(--beaker-surface); stroke-width: 2; stroke-linecap: round; opacity: 1; }
.acids-beaker .acids-solution { fill-opacity: 1; }
.acids-beaker .acids-particle-h { --particle-colour: #a43e37; }
.acids-beaker .acids-particle-oh { --particle-colour: #2b638a; }
.acids-beaker .acids-particle-a { --particle-colour: #25684a; }
.acids-beaker .acids-particle-ha { --particle-colour: #65574b; }
.acids-beaker .acids-particle-oh text { font-size: 13px; }
.acids-ion-float { animation: acids-ion-drift var(--ion-duration) ease-in-out var(--ion-delay) infinite alternate; }
@keyframes acids-ion-drift { from { transform: translate(-1.5px, 1.5px); } to { transform: translate(1.5px, -1.5px); } }
.acids-litmus-result { display: flex; align-items: center; gap: 12px; padding-top: 16px; border-top: 1px solid var(--color-border); }
.acids-litmus-change { display: inline-flex; flex-shrink: 0; align-items: center; gap: 5px; color: var(--color-text-muted); }
.acids-litmus-change i { display: block; width: 13px; height: 25px; border: 1px solid rgba(128, 128, 128, 0.2); border-radius: 2px; }
.acids-litmus-blue { background: #6387d1; }
.acids-litmus-red { background: #d9616c; }
.acids-litmus-both { background: linear-gradient(to right, #6387d1 50%, #d9616c 50%); }
.acids-page .acids-model-note { margin: 12px 0 24px; font-size: 0.7rem; }
.acids-acid-origin { margin-top: 24px; padding: 28px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-panel); }
.acids-transfer-heading { display: flex; align-items: flex-start; justify-content: space-between; gap: 24px; }
.acids-acid-origin h3 { margin: 0; font-size: 1.4rem; }
.acids-page .acids-transfer-intro { margin: 10px 0 0; font-size: 0.82rem; }
.acids-transfer-views { display: flex; flex-shrink: 0; gap: 7px; }
.acids-transfer-view { min-height: 44px; padding: 9px 13px; border: 1px solid var(--color-border); border-radius: 7px; background: transparent; color: var(--color-text-muted); font-size: 0.75rem !important; font-weight: 700 !important; white-space: nowrap; cursor: pointer; }
.acids-transfer-view:hover { border-color: var(--color-accent); }
.acids-transfer-view[aria-pressed="true"] { background: var(--color-accent); border-color: var(--color-accent); color: #241507; }
.acids-transfer-steps { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; margin: 27px 0 0; padding: 0; list-style: none; }
.acids-transfer-steps li { display: flex; align-items: center; gap: 9px; padding: 0 0 11px; border-bottom: 2px solid var(--color-border); color: var(--color-text-muted); font-size: 0.72rem; }
.acids-transfer-steps li span { display: grid; place-items: center; width: 22px; height: 22px; flex-shrink: 0; border: 1px solid var(--color-border); border-radius: 50%; font-size: 0.65rem; }
.acids-transfer-steps li.is-active { border-color: var(--color-accent); color: var(--color-accent); font-weight: 700; }
.acids-transfer-steps li.is-active span { background: var(--color-accent); border-color: var(--color-accent); color: #241507; }
.acids-transfer-steps li.is-done { border-color: var(--color-text-muted); }
.acids-transfer-scene { display: block; width: 100%; height: auto; fill: var(--color-text); }
.acids-transfer-scene circle { stroke-width: 1.6; }
.acids-transfer-scene text { text-anchor: middle; dominant-baseline: middle; font-family: Arial, sans-serif; }
.acids-transfer-symbol { font-size: 20px; font-weight: 700; }
.acids-transfer-charge { font-size: 23px; font-weight: 700; }
.acids-transfer-formula { font-size: 27px; font-weight: 700; }
.acids-transfer-state { font-size: 13px; font-weight: 400; fill: var(--color-text-muted); }
.acids-transfer-name { font-size: 14px; fill: var(--color-text-muted); }
.acids-transfer-operator { font-size: 27px; fill: var(--color-text-muted); }
.acids-transfer-footer { display: flex; align-items: center; justify-content: space-between; gap: 20px; border-top: 1px solid var(--color-border); padding-top: 17px; }
.acids-page .acids-transfer-caption { min-height: 22px; margin: 0; font-size: 0.82rem; }
.acids-transfer-playback { display: flex; flex-shrink: 0; gap: 8px; }
.acids-transfer-playback button { min-width: 80px; min-height: 44px; padding: 7px 11px; border: 1px solid var(--color-border); border-radius: 7px; background: transparent; color: var(--color-text); font-size: 0.72rem !important; font-weight: 700 !important; cursor: pointer; }
.acids-transfer-playback button:hover { border-color: var(--color-accent); background: var(--color-bg-card); }
.acids-page .acids-transfer-static-intro { margin: 28px 0 20px; font-size: 0.76rem; }
.acids-page .acids-transfer-static-caption { margin: 16px 0 0; padding-top: 16px; border-top: 1px solid var(--color-border); text-align: center; font-size: 0.82rem; }
.acids-reaction-wrap { min-width: 0; }
.acids-reaction { display: grid; grid-template-columns: minmax(0, 1fr) 32px minmax(0, 1fr); align-items: center; gap: 6px; }
.acids-reaction-side { display: grid; grid-template-columns: minmax(0, 1fr) 16px minmax(0, 1fr); align-items: center; gap: 4px; }
.acids-reaction-term { display: flex; flex-direction: column; align-items: center; min-width: 0; gap: 5px; }
.acids-molecule { display: block; width: 100%; max-width: 100px; height: auto; }
.acids-molecule circle { stroke-width: 1.5; }
.acids-molecule text { text-anchor: middle; dominant-baseline: middle; font: 700 14px Arial, sans-serif; }
.acids-atom-bond { fill: none; stroke: var(--color-text-muted); stroke-width: 1.5; stroke-linecap: butt; }
.acids-atom-chlorine { fill: var(--acids-neutral); fill-opacity: 0.15; stroke: var(--acids-neutral); }
.acids-atom-chlorine-label { fill: var(--acids-neutral); }
.acids-atom-oxygen { fill: var(--acids-hydroxide); fill-opacity: 0.15; stroke: var(--acids-hydroxide); }
.acids-atom-oxygen-label { fill: var(--acids-hydroxide); }
.acids-atom-hydrogen { fill: var(--color-bg-card); stroke: var(--color-text-muted); }
.acids-atom-hydrogen-label { fill: var(--color-text-muted); }
.acids-molecule-charge { fill: var(--color-text); }
.acids-equation-formula { color: var(--color-text); font-size: clamp(1rem, 1.6vw, 1.3rem); font-weight: 700; white-space: nowrap; }
.acids-equation-formula small { margin-left: 2px; color: var(--color-text-muted); font-size: 0.55em; font-weight: 400; }
.acids-equation-formula :is(sup, sub) { font-size: 0.65em; }
.acids-reaction-name { min-height: 2.8em; color: var(--color-text-muted); text-align: center; font-size: 0.65rem; line-height: 1.4; }
.acids-equation-symbol { color: var(--color-text-muted); text-align: center; font-size: 1.15rem; }
.acids-reaction-arrow { color: var(--color-accent); text-align: center; font-size: 2rem; }
.acids-page .acids-hydronium-note { margin: 18px 0 0; padding-top: 12px; border-top: 1px solid var(--color-border); font-size: 0.7rem; }
.acids-tenfold { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.15fr); align-items: center; gap: 36px; margin-top: 20px; padding: 28px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-panel); }
.acids-tenfold h3 { font-size: 1.2rem; }
.acids-tenfold p { margin: 0; font-size: 0.83rem; }
.acids-tenfold .acids-eyebrow { margin-bottom: 12px; font-size: 0.65rem; }
.acids-ph-steps { display: grid; grid-template-columns: minmax(0, 1fr) 28px minmax(0, 1fr) 28px minmax(0, 1fr); align-items: center; max-width: 440px; margin: 0 auto; }
.acids-ph-step { display: flex; flex-direction: column; align-items: center; gap: 8px; min-width: 0; }
.acids-ph-step-label { color: var(--color-text); font-size: 0.9rem; font-weight: 700; }
.acids-concentration-dots { display: grid; grid-template-columns: repeat(10, minmax(0, 1fr)); grid-template-rows: repeat(10, minmax(0, 1fr)); gap: 2px; width: 80px; height: 80px; padding: 6px; border: 1px solid var(--color-border); border-radius: 6px; background: var(--color-bg-card); }
.acids-concentration-dots i { border-radius: 50%; background: var(--acids-acidic); }
.acids-ph-step strong { color: var(--acids-acidic); font-size: 0.75rem; }
.acids-ph-step-arrow { display: flex; flex-direction: column; align-items: center; color: var(--color-accent); font-size: 0.7rem; font-weight: 700; line-height: 1.2; }
.acids-ph-step-arrow > :last-child { font-size: 1.5rem; }
.acids-tenfold .acids-dots-caption { margin-top: 14px; text-align: center; font-size: 0.65rem; }
.acids-details { margin-top: 22px; padding: 20px 24px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-panel); }
.acids-details summary { font-size: 0.95rem; font-weight: 700; cursor: pointer; }
.acids-strength-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 28px; margin-top: 24px; }
.acids-strength-grid h3 { font-size: 0.88rem; }
.acids-strength-grid p { margin: 0; font-size: 0.82rem; }
.acids-strength-grid > div { min-width: 0; }
.acids-mini-comparison { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin: 16px 0; }
.acids-mini-model { display: flex; flex-direction: column; align-items: center; min-width: 0; margin: 0; padding: 12px 6px; border: 1px solid var(--color-border); border-radius: 9px; background: var(--color-bg-card); }
.acids-mini-model figcaption { color: var(--color-text); font-size: 0.78rem; font-weight: 700; }
.acids-mini-model > span { color: var(--color-text-muted); text-align: center; font-size: 0.68rem; }
.acids-beaker-small { max-width: 200px; margin: 6px auto; }
.acids-beaker-small .acids-particle text { font-size: 14px; }
.acids-strength-takeaway { margin: 20px 0 0; padding-top: 15px; border-top: 1px solid var(--color-border); font-size: 0.8rem; }
.acids-lab { margin-top: 26px; }
.acids-lab-heading { display: flex; align-items: center; justify-content: space-between; gap: 18px; margin-bottom: 22px; }
.acids-lab-heading .acids-eyebrow { margin-bottom: 8px; }
.acids-lab-heading h3 { margin: 0; font-size: clamp(1.1rem, 2vw, 1.45rem); }
.acids-lab-heading > button { flex-shrink: 0; }
.acids-lab-choices { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 10px; min-width: 0; margin: 0; padding: 0; border: 0; }
.acids-lab-choices legend { margin-bottom: 12px; padding: 0; color: var(--color-text); font-size: 0.85rem; font-weight: 700; }
.acids-lab-choices button { display: flex; flex-direction: column; align-items: flex-start; gap: 4px; min-width: 0; padding: 15px 18px; border: 1px solid var(--color-border); border-radius: 10px; background: var(--color-bg-card); color: var(--color-text); text-align: left; cursor: pointer; }
.acids-lab-choices button:hover, .acids-lab-choices button[aria-pressed="true"] { border-color: var(--color-accent); box-shadow: inset 0 0 0 1px var(--color-accent); }
.acids-lab-choices strong { color: var(--color-accent); font-size: 1.1rem; }
.acids-lab-choices span { font-size: 0.78rem; }
.acids-lab-choices small { color: var(--color-text-muted); font-size: 0.7rem; }
.acids-lab-switch-note { margin: 10px 0 0; font-size: 0.72rem; }
.acids-lab-workspace { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr); gap: 28px; margin-top: 26px; }
.acids-lab-controls { min-width: 0; }
.acids-lab-control + .acids-lab-control { margin-top: 24px; padding-top: 22px; border-top: 1px solid var(--color-border); }
.acids-lab-control > label { color: var(--color-text); font-size: 0.85rem; font-weight: 700; }
.acids-page .acids-lab-control-value { display: flex; align-items: baseline; flex-wrap: wrap; gap: 6px 12px; margin: 10px 0 0; }
.acids-lab-control-value output { color: var(--color-text); font-size: 1.3rem; font-weight: 700; }
.acids-lab-control-value > span { font-size: 0.72rem; }
.acids-lab-control .acids-slider { display: block; margin: 0 0 8px; }
.acids-lab-stepper { display: flex; flex-wrap: wrap; gap: 8px; }
.acids-lab-stepper > button { flex: 1 1 130px; gap: 5px; padding: 8px 10px; font-size: 0.76rem !important; }
.acids-lab button:disabled { opacity: 0.45; cursor: default; }
.acids-page .acids-lab-control > p:last-child { margin: 10px 0 0; font-size: 0.7rem; }
.acids-page .acids-lab-prompt { margin: 20px 0 0; padding: 12px 15px; border-left: 3px solid var(--color-accent); background: var(--color-bg-card); font-size: 0.75rem; }
.acids-lab-model { display: flex; flex-direction: column; justify-content: space-between; min-width: 0; padding: 18px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-card); }
.acids-lab-model-heading { display: flex; align-items: center; justify-content: space-between; gap: 10px; color: var(--color-text-muted); font-size: 0.65rem; letter-spacing: 0.08em; }
.acids-lab-model-heading > :last-child { color: var(--color-text); font-size: 0.8rem; font-weight: 700; letter-spacing: 0; }
.acids-lab-beaker { width: min(100%, 340px); max-width: 340px; margin: 0 auto; }
.acids-lab-beaker .acids-particle text { font-size: 12px; }
.acids-lab-particle-key { display: flex; align-items: center; justify-content: center; flex-wrap: wrap; gap: 6px 16px; color: var(--color-text); font-size: 0.72rem; }
.acids-lab-particle-key > span { display: inline-flex; align-items: center; gap: 5px; }
.acids-lab-dot { width: 11px; height: 11px; flex-shrink: 0; border: 1px solid currentColor; border-radius: 50%; }
.acids-lab-dot[data-particle="h"] { background: #df8275; color: #a43e37; }
.acids-lab-dot[data-particle="a"] { background: #80b799; color: #25684a; }
.acids-lab-dot[data-particle="ha"] { background: #c3b2a1; color: #65574b; }
.acids-page .acids-lab-particle-count { margin: 12px 0 0; text-align: center; font-size: 0.67rem; }
.acids-lab-results { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 20px; margin-top: 24px; padding: 20px 0 0; border-top: 1px solid var(--color-border); }
.acids-lab-results > div { min-width: 0; }
.acids-lab-results > div > span { display: block; margin-bottom: 7px; color: var(--color-text-muted); font-size: 0.6rem; letter-spacing: 0.09em; }
.acids-lab-results strong { display: block; color: var(--color-accent); font-size: clamp(1.05rem, 2vw, 1.45rem); line-height: 1.3; }
.acids-lab-results p { margin: 8px 0 0; font-size: 0.73rem; }
.acids-lab .acids-model-note { margin-bottom: 0; }
.acids-uses-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 14px; }
.acids-use-card { display: flex; flex-direction: column; align-items: flex-start; min-width: 0; padding: 22px 20px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-panel); }
.acids-use-category { color: var(--color-text-muted); font-size: 0.58rem; letter-spacing: 0.1em; }
.acids-use-illustration { display: block; width: 100%; height: auto; max-height: 180px; margin: 16px 0 20px; border-radius: 9px; background: radial-gradient(ellipse at center, rgba(238, 172, 96, 0.07), transparent 75%); object-fit: contain; color-scheme: inherit; }
.acids-formula { display: block; margin: 0 0 14px; color: var(--color-accent); font-size: clamp(1.1rem, 1.5vw, 1.5rem); font-weight: 700; }
.acids-formula sub { font-size: 0.65em; }
.acids-use-card h3 { margin-bottom: 0; font-size: 1rem; }
.acids-use-card p { flex: 1; font-size: 0.8rem; }
.acids-use-tag { padding-top: 13px; border-top: 1px solid var(--color-border); width: 100%; color: var(--color-accent); font-size: 0.67rem; }
.acids-measuring { margin-top: 28px; padding: 26px; border: 1px solid var(--color-border); border-radius: 12px; background: var(--color-bg-panel); }
.acids-measuring .acids-section-intro { margin-bottom: 0; font-size: 0.83rem; }
.acids-measuring-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 28px; }
.acids-measure-number { font-size: 0.65rem; color: var(--color-accent); }
.acids-measuring h4 { margin: 8px 0; font-size: 0.9rem; }
.acids-measuring-grid p { margin: 0; font-size: 0.8rem; }
.acids-note { margin: 24px 0 0; padding: 16px 18px; border-left: 3px solid var(--color-accent); border-radius: 0 8px 8px 0; background: var(--color-bg-card); font-size: 0.8rem; }
.acids-note a { display: inline-block; }
.acids-quiz-progress { display: flex; align-items: center; flex-wrap: wrap; gap: 16px; margin-bottom: 26px; color: var(--color-text-muted); font-size: 0.78rem; }
.acids-quiz-progress progress { flex: 1; min-width: 75px; height: 7px; accent-color: var(--color-accent); }
.acids-question { min-width: 0; margin: 0 0 22px; padding: 0; border: 0; }
.acids-question legend { width: 100%; margin-bottom: 20px; padding: 0; font-size: 1.15rem; font-weight: 700; line-height: 1.5; }
.acids-answer-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.acids-answer { display: flex; align-items: flex-start; gap: 12px; padding: 15px; min-height: 60px; border: 1px solid var(--color-border); border-radius: 9px; background: var(--color-bg-card); color: var(--color-text-muted); font-size: 0.85rem; cursor: pointer; }
.acids-answer input { flex-shrink: 0; margin: 5px 0 0; accent-color: var(--color-accent); }
.acids-answer:has(input:enabled):hover, .acids-answer:has(input:enabled:checked) { border-color: var(--color-accent); color: var(--color-text); }
.acids-answer:has(input:disabled) { cursor: default; }
.acids-answer.is-correct { border-color: var(--acids-success); }
.acids-answer.is-incorrect { border-color: var(--acids-error); }
.acids-answer-state { display: block; color: var(--acids-success); font-size: 0.7rem; }
.acids-answer-state:not(:empty) { margin-top: 7px; }
.acids-answer.is-incorrect .acids-answer-state { color: var(--acids-error); }
.acids-feedback { margin-bottom: 22px; padding: 18px 20px; border: 1px solid var(--color-border); border-left: 3px solid var(--acids-success); border-radius: 8px; background: var(--color-bg-card); font-size: 0.85rem; }
.acids-feedback > strong { color: var(--acids-success); }
.acids-feedback p { margin: 7px 0 10px; }
.acids-feedback a { font-size: 0.76rem; }
.acids-feedback.is-incorrect { border-left-color: var(--acids-error); }
.acids-feedback.is-incorrect > strong { color: var(--acids-error); }
.acids-results h3 { font-size: 1.8rem; }
.acids-results > p { font-size: 0.9rem; }
.acids-review { display: grid; gap: 12px; margin: 24px 0; padding: 0; list-style: none; }
.acids-review li { padding: 18px 20px; border: 1px solid var(--color-border); border-left: 3px solid var(--acids-success); border-radius: 9px; background: var(--color-bg-card); font-size: 0.82rem; }
.acids-review li.is-incorrect { border-left-color: var(--acids-error); }
.acids-review li > strong { color: var(--acids-success); }
.acids-review li.is-incorrect > strong { color: var(--acids-error); }
.acids-review p { margin: 8px 0 0; }
.acids-review a { display: inline-block; margin-top: 10px; font-size: 0.75rem; }
.acids-sources { margin: 32px 0 4px; text-align: center; }
.acids-sources .acids-eyebrow { font-size: 0.6rem; }
.acids-sources > p:last-child { font-size: 0.73rem; }
:root[data-theme="light"] .acids-page { --acids-acidic: #a43e37; --acids-neutral: #25684a; --acids-alkaline: #5d4b9c; --acids-hydroxide: #2b638a; --acids-success: #25684a; --acids-error: #a43e37; }
:root[data-theme="light"] .acids-beaker { --beaker-glass: #7a6b5e; --beaker-surface: #83aab5; --beaker-liquid-top: #e5f0f2; --beaker-liquid-bottom: #c6dfe5; }
:root[data-theme="light"] .acids-button-primary { background: var(--color-accent); color: #fffaf4 !important; }
:root[data-theme="light"] .acids-button-primary:hover { background: var(--color-accent-dark); }
:root[data-theme="light"] .acids-transfer-view[aria-pressed="true"], :root[data-theme="light"] .acids-transfer-steps li.is-active span { color: #fffaf4; }
@media (max-width: 1200px) {
    .acids-hero { gap: 24px; }
    .acids-explorer-layout { grid-template-columns: minmax(0, 1.5fr) minmax(210px, 1fr); gap: 20px; }
    .acids-readout { gap: 12px; padding: 20px 16px; }
    .acids-indicator { width: 35px; }
    .acids-indicator-paper { left: 10px; }
    .acids-uses-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 760px) {
    .acids-transfer-heading { flex-direction: column; gap: 16px; }
    .acids-transfer-steps { gap: 8px; }
    .acids-transfer-steps li { align-items: flex-start; gap: 6px; font-size: 0.68rem; }
    .acids-transfer-scene { min-height: 205px; }
    .acids-lab-workspace { grid-template-columns: 1fr; gap: 22px; }
    .acids-lab-model { min-height: 330px; }
    .acids-lab-choices button { padding: 12px; }
    .acids-hero { grid-template-columns: 1fr; padding-top: 12px; }
    .acids-hero-art { min-height: 250px; }
    .acids-hero-number { font-size: 5rem; }
    .acids-explorer-layout { grid-template-columns: 1fr; }
    .acids-readout { padding: 22px; }
    .acids-indicator { width: 43px; height: 150px; margin: 0 14px; }
    .acids-indicator-paper { left: 14px; }
    .acids-concept-grid { grid-template-columns: 1fr; }
    .acids-section-heading { align-items: flex-start; flex-wrap: wrap; gap: 10px; }
    .acids-strength-grid, .acids-measuring-grid { grid-template-columns: 1fr; gap: 20px; }
    .acids-formula { font-size: 1.4rem; }
}
@media (max-width: 1000px) {
    .acids-transfer-heading { flex-wrap: wrap; }
    .acids-tenfold { grid-template-columns: 1fr; gap: 24px; }
}
@media (max-width: 900px) {
    .acids-concept-grid { grid-template-columns: 1fr; }
}
@media (max-width: 600px) {
    .acids-transfer-acid-group { transform: translateX(-117px); }
    .acids-transfer-water-group { transform: translateX(-334px); }
    .acids-transfer-operator { transform: translateX(-219px); }
}
@media (max-width: 480px) {
    .acids-transfer-footer { align-items: flex-start; flex-direction: column; gap: 12px; }
    .acids-transfer-steps li { flex-direction: column; }
    .acids-lab-heading { align-items: flex-start; flex-direction: column; }
    .acids-lab-choices { grid-template-columns: 1fr; gap: 8px; }
    .acids-lab-choices button { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.2fr); align-items: center; gap: 0 8px; }
    .acids-lab-choices strong { grid-row: span 2; font-size: 1rem; }
    .acids-lab-results { grid-template-columns: 1fr; gap: 18px; }
    .acids-lab-results > div + div { padding-top: 16px; border-top: 1px solid var(--color-border); }
    .acids-page { padding-top: 0; }
    .acids-hero h1 { font-size: 2.5rem; }
    .acids-panel { padding: 18px 14px; }
    .acids-scale-zones { gap: 2px; }
    .acids-scale { gap: 2px; }
    .acids-scale-stop { height: 56px; border-width: 1px; font-size: 0.65rem !important; }
    .acids-uses-grid, .acids-answer-grid { grid-template-columns: 1fr; }
    .acids-use-card { padding: 22px; }
    .acids-use-illustration { max-height: 190px; }
    .acids-acid-origin, .acids-tenfold { padding: 20px; }
    .acids-reaction { grid-template-columns: 1fr; gap: 0; }
    .acids-reaction-side { grid-template-columns: minmax(0, 1fr) 24px minmax(0, 1fr); }
    .acids-reaction-arrow { justify-self: center; transform: rotate(90deg); }
    .acids-equation-formula { font-size: 1.2rem; }
    .acids-ph-steps { grid-template-columns: minmax(0, 1fr) 24px minmax(0, 1fr) 24px minmax(0, 1fr); }
    .acids-concentration-dots { width: 58px; height: 58px; padding: 4px; gap: 1.5px; }
    .acids-details, .acids-measuring { padding: 20px; }
    .acids-lesson { margin: 34px 0; }
}
@media (max-width: 360px) { .acids-mini-comparison { grid-template-columns: 1fr; } }
@media (prefers-reduced-motion: reduce) { .acids-page *, .acids-page *::before, .acids-page *::after { transition: none !important; animation: none !important; } }

/* Compact solution card and motion controls. */
.acids-lab-model { align-self: start; justify-content: flex-start; gap: 10px; min-height: 0; }
.acids-lab-model-heading { flex-wrap: wrap; gap: 8px; }
.acids-lab-model-heading > :first-child { margin-right: auto; }
.acids-lab-model-heading #acidsLabVolume { color: var(--color-text); font-size: 0.8rem; font-weight: 700; letter-spacing: 0; white-space: nowrap; }
.acids-lab-model-heading > .acids-lab-motion-toggle { flex-shrink: 0; min-height: 32px; margin: 0; padding: 5px 10px; font-size: 0.68rem !important; font-weight: 400; letter-spacing: 0; }
.acids-page .acids-lab-model .acids-lab-particle-count { margin: 0; }