:root{--ink:#2c2945;--muted:#837e94;--green:#7656bc;--line:#eae5f4;--bg:#f8f7fd}body{font-family:Arial,'Microsoft YaHei',sans-serif}aside{width:208px;padding:25px 18px}main{margin-left:208px;padding:30px 45px}.brand{font-size:23px;line-height:1.2;color:#273149}.mark{background:#efebfc;color:#8466c2;width:36px;height:36px;border-radius:10px}.eyebrow{color:#8269b4}nav{margin-top:27px}nav button{font-size:12px;min-height:60px;border-left:3px solid transparent}nav button.active{background:#efebfb;color:#7053b1;border-left-color:#9570d5}nav small{font-size:11px}h1,h2{color:#30284e}header{margin-bottom:22px}.hero{background:linear-gradient(105deg,#eee7fc,#ede9fb 65%,#e4f3ee);border:0;padding:28px;border-radius:18px;min-height:238px}.hero h2{font-size:28px;max-width:70%;font-weight:800}.hero p{color:#7c7890}.primary{background:#7656bc;box-shadow:0 5px 12px #7656bc15}.avatar{background:#eee7fc}.tag{color:#7656bc;border-color:#e6dff2}.preview-strip{display:flex;justify-content:space-between;gap:20px;align-items:center;background:#f0ebfa;border:1px solid #e3d9f2;border-radius:12px;padding:16px 18px;margin:27px 0 20px}.preview-strip p{font-size:12px;margin:0;color:#645b7b}.preview-strip button{font-size:11px}.ref-home-cards{margin-top:20px}.ref-home-cards .card{border:0;padding:20px 14px;min-height:127px}.ref-home-cards .icon{background:none!important;margin-bottom:12px;width:auto;height:25px;display:block;font-size:22px}.ref-home-cards p{min-height:0;margin:0;color:#645b7b}.ref-home-cards strong{font-size:13px}.ref-home-cards .go{display:none}.home-title{font-size:31px;font-weight:900;color:#253049;letter-spacing:-1px}.teacher-avatar{position:absolute;right:35px;top:40px;border:6px solid white;border-radius:50%;width:115px;height:115px;background:#d8e8e9;color:#7656bc;display:grid;place-items:center;font-size:26px;font-weight:900;box-shadow:0 0 0 8px #ffffff33}.small-copy{font-size:12px;color:#847c92}.labs-toolbar{display:flex;align-items:end;gap:12px;flex-wrap:wrap;background:white;border:1px solid var(--line);border-radius:12px;padding:16px;margin-bottom:18px}.labs-toolbar label{font-size:11px;color:#7d728d;display:block}.labs-toolbar select,.labs-toolbar input{padding:9px 12px;border:1px solid #dfd6ed;background:#fff;border-radius:7px;color:var(--ink);min-height:41px}.labs-toolbar .field-grow{flex:1;min-width:210px}.labs-toolbar input{width:100%}.segmented{display:flex;gap:5px;background:#f1edf9;padding:5px;border-radius:9px}.segmented button{border:0;background:none;padding:8px 15px;border-radius:6px;color:#706583}.segmented button.on{background:white;color:#7053b1;box-shadow:0 2px 4px #76658d15}.lab-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.lab-card{border:1px solid var(--line);border-radius:13px;background:white;padding:20px;display:flex;flex-direction:column;text-align:left;min-height:210px;color:var(--ink);transition:.15s}.lab-card:hover{box-shadow:0 7px 22px #69539312;transform:translateY(-2px)}.lab-card .lab-card-meta{font-size:10px;text-transform:uppercase;letter-spacing:.7px;color:#8a729f}.lab-card h3{font-size:16px;line-height:1.45;margin:13px 0 6px}.lab-card p{font-size:11px;line-height:1.55}.lab-card footer{margin-top:auto;padding-top:17px;display:flex;justify-content:space-between;font-size:11px;color:#7656bc}.lab-mini-icon{width:36px;height:36px;background:#eee9fb;border-radius:9px;display:grid;place-items:center;font-size:21px;margin-bottom:12px}.labs-section-title{display:flex;align-items:center;justify-content:space-between;margin:22px 0 12px}.sources-box{background:#f0ecf7;border-radius:12px;padding:18px;margin-top:24px;font-size:12px}.sources-box a{color:#7656bc;margin-right:16px;text-decoration:none}.lab-sim-layout{display:grid;grid-template-columns:280px minmax(0,1fr);gap:20px;align-items:start}.lab-controls{background:white;border:1px solid var(--line);border-radius:13px;padding:22px;position:sticky;top:20px}.lab-condition{width:100%;text-align:left;background:white;border:1px solid #e7dff1;border-radius:8px;padding:12px;margin-top:9px;color:var(--ink);font-size:12px}.lab-condition.selected{background:#f0ebfa;border-color:#a48bd3;color:#684b9d}.lab-condition small{display:block;color:#81728e;font-size:10px}.lab-condition[aria-pressed=true]{box-shadow:inset 3px 0 #9570d5}.sim-card{border:1px solid var(--line);border-radius:13px;background:white;overflow:hidden}.sim-scene{min-height:280px;background:radial-gradient(ellipse at 50% 30%,#fff,#f2edf9);padding:20px;display:flex;flex-direction:column;align-items:center;justify-content:center;position:relative}.sim-scene .scene-caption{font-size:10px;text-transform:uppercase;letter-spacing:1px;color:#8c7c9b;position:absolute;top:17px;left:20px}.sim-vessel{width:105px;height:145px;border:4px solid #a9b9c5;border-top:0;border-radius:0 0 23px 23px;position:relative;overflow:hidden;background:#ffffffaa;box-shadow:6px 6px 0 #dbe1eb55;margin-top:25px}.sim-liquid{position:absolute;bottom:0;width:100%;height:63%;background:var(--fluid,#d6e9f5);opacity:.82;transition:background 900ms}.sim-liquid:after{content:'';position:absolute;width:100%;height:3px;background:#fff7;top:2px}.sim-sediment{position:absolute;bottom:0;width:100%;height:17px;background:var(--solid,#a76f47);opacity:0;transition:opacity .6s}.sim-vessel.after .sim-sediment{opacity:1}.sim-symbol{font-size:17px;font-weight:bold;margin-top:18px;color:#554264;text-align:center;max-width:90%}.sim-subtitle{font-size:11px;text-align:center;color:#8b7d93;margin-top:6px}.gas-particle{position:absolute;border:2px solid #fff8;width:9px;height:9px;border-radius:50%;bottom:5px;animation:gasrise 1.6s linear infinite;left:30%}.gas-particle:nth-child(2){left:70%;animation-delay:-.6s}.gas-particle:nth-child(3){left:46%;animation-delay:-1.2s}.gas-particle:nth-child(4){left:18%;animation-delay:-.8s}.foam-cap{position:absolute;top:42px;left:0;right:0;height:30px;background:radial-gradient(circle at 8px 10px,#fff 7px,#c8d6e5 8px,transparent 9px) 0 0/18px 18px}.sim-bulb{width:72px;height:72px;border:4px solid #b4b8c6;border-radius:50%;margin:20px auto 0;background:var(--fluid);box-shadow:0 0 40px var(--fluid);position:relative}.sim-bulb:after{content:'';position:absolute;bottom:-29px;left:16px;width:30px;height:23px;background:repeating-linear-gradient(#8f91a4 0 4px,#c2c5d5 4px 8px);border-radius:0 0 5px 5px}.sim-gauge{height:155px;width:28px;border-radius:20px;border:3px solid #b5a9be;background:#fff;display:flex;align-items:end;padding:3px;position:relative;margin:20px 0 0}.sim-gauge div{width:100%;height:var(--level,50%);background:var(--fluid);border-radius:20px;transition:height .8s}.sim-gauge:after{content:'°C';position:absolute;left:35px;top:10px;color:#82748c;font-size:16px}.sim-stretch{width:210px;height:20px;border-radius:20px;background:var(--fluid);margin:60px 0 30px;animation:stretch 2s ease-in-out infinite;transform-origin:center}.sim-particles{width:150px;display:grid;grid-template-columns:repeat(5,1fr);gap:6px;margin:45px 0 20px}.sim-particles i{width:21px;height:21px;background:var(--fluid);border-radius:50%;box-shadow:inset -3px -3px #0001}.sim-particles i:nth-child(7n){background:#b892cc}.sim-move i{animation:jiggle 1s ease-in-out infinite alternate}.sim-move i:nth-child(3n){animation-delay:-.6s}.sim-results{padding:23px}.result-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px}.result-block{background:#f7f4fb;padding:18px;border-radius:10px}.result-block b{font-size:12px;color:#8062a4}.result-block p{color:#4d425a;font-size:13px;margin-top:9px}.why-block{border-left:3px solid #a287cd;padding:0 16px;margin:20px 0}.why-block p{color:#645971;font-size:13px}.equation-box{background:#eeebf5;padding:13px;border-radius:8px;font-size:14px;font-family:Arial,sans-serif;white-space:pre-line}.lab-note{width:100%;min-height:85px;padding:13px;border:1px solid #e0d7ec;border-radius:8px;resize:vertical;font:inherit;margin-top:10px}.lab-footer-actions{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-top:18px}.lab-reference{font-size:11px;color:#8b7c96}.lab-reference a{color:#7656bc}.lab-empty{text-align:center;padding:45px 20px;border:1px dashed #dcd1ed;border-radius:12px;color:#81718c;grid-column:1/-1}.sr-only{position:absolute;clip:rect(0,0,0,0);width:1px;height:1px;overflow:hidden}@keyframes gasrise{to{transform:translateY(-120px);opacity:0}}@keyframes stretch{50%{transform:scaleX(1.25)}}@keyframes jiggle{to{transform:translate(2px,-3px)}}@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}@media(max-width:1100px){.lab-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.lab-sim-layout{grid-template-columns:230px minmax(0,1fr)}main{padding:25px}}@media(max-width:760px){aside{width:100%;padding:17px;position:relative}.brand{font-size:20px}main{margin-left:0;padding:19px}nav{margin-top:14px}.home-title{font-size:25px}.hero h2{font-size:24px;max-width:100%}.teacher-avatar{display:none}.lab-sim-layout{grid-template-columns:1fr}.lab-controls{position:static}.lab-condition{width:calc(50% - 5px);display:inline-block;vertical-align:top;min-height:65px}.result-grid{grid-template-columns:1fr}.preview-strip{padding:14px;align-items:start}.lab-grid{grid-template-columns:1fr 1fr}.lab-card{padding:15px;min-height:220px}.lab-card h3{font-size:14px}.lab-card footer{display:block}.hero{padding:25px}.sim-scene{min-height:260px}}@media(max-width:430px){.lab-grid{grid-template-columns:1fr}.lab-card{min-height:170px}.lab-card footer{display:flex}.labs-toolbar .segmented{width:100%}.result-grid{gap:10px}.top{display:block}.lab-condition{width:100%}}

.lab-chapters{display:grid;gap:22px}.lab-chapter-group{--chapter-bg:#f0ebfa;--chapter-accent:#7656bc;border:1px solid var(--line);border-left:4px solid var(--chapter-accent);border-radius:13px;background:var(--chapter-bg);overflow:hidden}.lab-chapter-heading{display:flex;align-items:center;gap:12px;padding:18px 20px;color:var(--ink)}.lab-chapter-number{font-size:12px;font-weight:700;color:var(--chapter-accent);white-space:nowrap}.lab-chapter-name{font-weight:700;flex:1;min-width:0}.lab-chapter-count{font-size:12px;color:#645b70;white-space:nowrap}.lab-chapter-group>.lab-grid{padding:0 16px 16px}.lab-chapter-color-1{--chapter-bg:#edf3fd;--chapter-accent:#4266a1}.lab-chapter-color-2{--chapter-bg:#edf6f1;--chapter-accent:#36745c}.lab-chapter-color-3{--chapter-bg:#fff3e8;--chapter-accent:#975d2b}.lab-chapter-color-4{--chapter-bg:#f1ecfa;--chapter-accent:#7656bc}.lab-chapter-color-5{--chapter-bg:#fceef2;--chapter-accent:#a14b68}.lab-chapter-color-6{--chapter-bg:#eaf5f6;--chapter-accent:#317680}.lab-chapter-color-7{--chapter-bg:#faf5e5;--chapter-accent:#816820}.lab-chapter-color-8{--chapter-bg:#eef0fa;--chapter-accent:#5c62a1}@media(max-width:600px){.lab-chapter-heading{gap:8px;padding:14px;flex-wrap:wrap}.lab-chapter-name{flex-basis:65%}.lab-chapter-count{margin-left:auto}.lab-chapter-group>.lab-grid{padding:0 10px 10px}}

/* Persistent brand, profile and language bar across all pages. */
body{padding-top:78px}main>header{position:fixed;top:0;left:0;right:0;height:78px;padding:12px 24px;margin:0;background:#fff;border-bottom:1px solid var(--line);z-index:1000;gap:16px;box-shadow:0 3px 12px #30284e08}.site-header-brand{font-size:22px;line-height:1.2;font-weight:800;color:#273149;white-space:nowrap}.site-header-brand span{color:#83a078}header .breadcrumb{display:none}header .profile{margin-left:auto;gap:14px;flex-shrink:0}aside{top:78px;height:calc(100vh - 78px)}aside>.brand,aside>.mark{display:none}#site-language-control{margin:0}html{scroll-padding-top:90px}.lab-controls{top:90px}@media(max-width:760px){main>header{height:78px;padding:10px 14px}.site-header-brand{font-size:19px}header .profile>span{display:none}aside{top:auto;height:auto}header .profile{gap:8px}#site-language-control span{display:none}#site-language-control select{max-width:140px}.avatar{width:32px;height:32px}}@media(max-width:420px){main>header{gap:8px;padding:10px}.site-header-brand{font-size:16px;white-space:normal;max-width:128px}#site-language-control select{max-width:126px;font-size:12px}}

/* Compact fixed navigation below the brand/language bar. */
body{padding-top:116px}main>header{height:64px;padding:8px 22px}aside{display:contents}aside>.eyebrow,aside>footer{display:none}#nav{position:fixed;top:64px;left:0;right:0;z-index:999;display:flex;align-items:center;gap:4px;height:52px;margin:0;padding:6px 18px;background:#fff;border-bottom:1px solid var(--line);overflow-x:auto;white-space:nowrap;scrollbar-width:thin}#nav button{flex:0 0 auto;width:auto;min-height:34px;margin:0;padding:7px 11px;gap:7px;border-left:0;border-radius:7px;font-size:12px;line-height:1.35;align-items:center}#nav button small{display:none}#nav button.active{border-left:0;box-shadow:inset 0 -2px #9570d5}main{margin-left:auto;margin-right:auto;padding:22px 32px;max-width:1600px}html{scroll-padding-top:128px}.lab-controls{top:128px}@media(max-width:760px){main>header{height:64px;padding:8px 14px}#nav{top:64px;padding:6px 10px;gap:3px}#nav button{padding:7px 9px;font-size:12px}main{margin-left:0;padding:18px 14px}}@media(max-width:420px){main>header{padding:8px 10px}}

.site-header-brand{display:flex;align-items:center;gap:10px;min-width:0}.site-brand-logo{display:block;width:38px;height:38px;flex-shrink:0}.site-brand-copy{color:#273149}@media(max-width:760px){.site-brand-logo{width:32px;height:32px}.site-header-brand{gap:7px}}@media(max-width:420px){.site-header-brand{max-width:none;flex:1;min-width:0;font-size:14px}.site-brand-copy{white-space:normal}.site-brand-logo{width:29px;height:29px}}

.site-brand-logo{object-fit:contain;width:44px;height:44px}@media(max-width:760px){.site-brand-logo{width:36px;height:36px}}@media(max-width:420px){.site-brand-logo{width:32px;height:32px}}

/* Equation-led salt selection: properties stay directly below their substance. */
.salt-properties-reaction{display:flex;flex-wrap:wrap;align-items:stretch;gap:8px;margin:12px 0}.salt-species-card{flex:1 1 145px;min-width:0;border:1px solid #bcd7e8;border-top:4px solid #5589b7;background:#f3f8fd;border-radius:12px;padding:12px}.salt-species-card.right{border-color:#b8d8c7;border-top-color:#519976;background:#f3faf6}.salt-prop-sign{align-self:center;color:#756393;font-size:22px}.salt-equation-select{display:block}.salt-equation-select span{font-size:11px;display:block;margin-bottom:5px}.salt-equation-select select{width:100%;max-width:100%;min-width:0;padding:8px 5px;font-size:16px;border:1px solid #9dabc4;border-radius:7px;background:white;color:#293b55}.salt-auto-formula,.salt-balanced-term{display:block;font-size:17px;margin:7px 0 10px;overflow-wrap:anywhere}.salt-species-card dl{margin:8px 0 0}.salt-species-card dl div{margin:7px 0}.salt-species-card dt{font-size:11px;color:#637085}.salt-species-card dd{margin:2px 0 0;font-size:13px;font-weight:600;overflow-wrap:anywhere}.salt-species-card dd i{display:inline-block;width:12px;height:12px;border-radius:50%;border:1px solid #aab6c7;margin-right:5px;vertical-align:middle}.salt-properties>p{margin:7px 0}.salt-no-reaction{color:#a02f4a;background:#fff1f4;border-radius:8px;padding:10px}.salt-properties-reaction+.salt-no-reaction{font-weight:600}@media(max-width:600px){.salt-species-card{flex-basis:125px}.salt-prop-sign{font-size:17px}.salt-properties{padding:14px}.salt-properties-reaction{gap:5px}}

.salt-setup-options{display:flex;justify-content:flex-end;padding:12px 16px;border-bottom:1px solid #e4deef;background:#faf8ff}.salt-setup-options label{display:flex;align-items:flex-start;gap:8px;max-width:410px;font-size:13px;font-weight:600;cursor:pointer}.salt-setup-options input{width:17px;height:17px;flex-shrink:0;margin:2px 0;accent-color:#8064af}.salt-setup-options small{display:block;font-size:11px;font-weight:400;line-height:1.5;margin-top:4px;color:#68748b}

/* Official brand logo in the Overview hero; preserve the complete artwork. */
.teacher-avatar{background:#fff;overflow:hidden}.teacher-avatar img{display:block;width:100%;height:100%;object-fit:contain}

/* Shared property rows align every substance beneath its equation term. */
.salt-substance-table{width:100%;table-layout:fixed;border-collapse:separate;border-spacing:0;margin:14px 0;border:1px solid #d9ddea;border-radius:12px;overflow:hidden}.salt-substance-table th,.salt-substance-table td{padding:12px 14px;text-align:left;vertical-align:middle;border-bottom:1px solid #dfe4ee;overflow-wrap:anywhere;font-size:13px}.salt-substance-table tr:last-child>*{border-bottom:0}.salt-substance-table tr>:first-child{width:15%;background:#f1eff8;color:#514569;font-weight:700}.salt-substance-table .left{background:#f3f8fd}.salt-substance-table .right{background:#f3faf6}.salt-substance-table thead th{position:relative;vertical-align:bottom;border-top:4px solid #5589b7}.salt-substance-table thead th.right{border-top-color:#519976}.salt-substance-table thead th:first-child{border-top-color:#9283ae}.salt-table-sign{position:absolute;left:-9px;top:45%;font-size:21px;color:#756393;z-index:1;background:#fff;border-radius:5px}.salt-substance-table td i{display:inline-block;width:12px;height:12px;border-radius:50%;border:1px solid #aab6c7;margin-right:5px;vertical-align:middle}@media(max-width:600px){.salt-substance-table th,.salt-substance-table td{padding:8px 5px;font-size:11px}.salt-substance-table tr>:first-child{width:20%}.salt-substance-table .salt-auto-formula,.salt-substance-table .salt-balanced-term{font-size:12px}.salt-substance-table select{font-size:12px;padding:6px 2px}.salt-substance-table .salt-equation-select span{font-size:10px}.salt-table-sign{font-size:13px;left:-5px}}

/* Equation operators share the formula baseline, below any selector. */
.salt-substance-table thead th{padding-bottom:16px}.salt-substance-table .salt-auto-formula,.salt-substance-table .salt-balanced-term{line-height:24px;margin-bottom:0}.salt-substance-table .salt-table-sign{top:auto;bottom:16px;line-height:24px}
@media(max-width:760px){.hero{isolation:isolate}.hero::after{content:"";position:absolute;right:-38px;top:50%;transform:translateY(-50%) rotate(-12deg);width:220px;height:220px;background:url('logo.png?v=95') center/contain no-repeat;opacity:.09;pointer-events:none;z-index:-1}.hero .teacher-avatar{display:none}.hero h2,.hero p{max-width:100%}.hero h2{position:relative}}
@media(max-width:600px){.salt-substance-table thead th{padding-bottom:10px}.salt-substance-table .salt-table-sign{bottom:10px}}

/* Selected formula is the equation term; no duplicated formula below it. */
.salt-substance-table thead th{vertical-align:bottom}.salt-substance-table .salt-equation-select{margin:0}.salt-substance-table .salt-equation-select select{line-height:24px}.salt-substance-table .salt-table-sign{bottom:24px}.salt-substance-table .salt-auto-formula{padding-bottom:8px}@media(max-width:600px){.salt-substance-table .salt-table-sign{bottom:16px}.salt-substance-table .salt-auto-formula{padding-bottom:6px}}

/* One compact equation row: only formulas and selects, no visible field captions. */
.salt-substance-table thead th{vertical-align:middle}.salt-substance-table .salt-auto-formula{padding:0;margin:0;line-height:24px}.salt-substance-table .salt-equation-select select{min-height:42px}.salt-substance-table .salt-table-sign{top:50%;bottom:auto;transform:translateY(-50%)}

/* Operators have their own narrow column, centred between substance columns. */
.salt-substance-table .salt-operator-cell{width:30px;padding:0;text-align:center;background:#fff;border-top:0;color:#756393;font-size:23px;vertical-align:middle}.salt-substance-table tbody .salt-operator-cell{font-size:inherit}@media(max-width:600px){.salt-substance-table .salt-operator-cell{width:18px;font-size:17px;padding:0}}

/* Blend operator gutters into adjoining substance colours instead of white stripes. */
.salt-substance-table .salt-operator-cell{background:#f3f8fd}.salt-substance-table .right+.salt-operator-cell{background:#f3faf6}.salt-substance-table .left+.salt-operator-cell:has(+.right){background:linear-gradient(90deg,#f3f8fd,#f3faf6)}

/* Keep the equation header continuous without dark accent strips. */
.salt-substance-table thead th,.salt-substance-table thead th.right,.salt-substance-table thead th:first-child{border-top:0}

/* Narrow row labels leave more room for formulas and dropdowns. */
.salt-substance-table tr>:first-child{width:11%;padding-left:9px;padding-right:9px}@media(max-width:600px){.salt-substance-table tr>:first-child{width:15%;padding-left:5px;padding-right:5px}}

.salt-substance-table td i{margin-right:0;margin-left:5px}

/* Compact catalogue cards; focus activities retain their own layout. */
#lab-cards .lab-card{min-height:0;padding:13px 15px}#lab-cards .lab-card h3{margin:7px 0 4px;font-size:14px}#lab-cards .lab-card p{min-height:0;margin:3px 0;font-size:12px}#lab-cards .lab-card footer{padding-top:8px}#lab-cards .lab-mini-icon{width:27px;height:27px;font-size:17px;margin-bottom:6px}#lab-cards .lab-grid{gap:10px}