:root{--navy:#071d35;--blue:#1676c9;--ice:#e8f3fb;--white:#fff;--ink:#102338;--muted:#607387;--line:#cad8e4;--good:#08775a;--bad:#a53636;--shadow:0 20px 60px rgba(7,29,53,.12)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;font-family:Arial,Helvetica,sans-serif;color:var(--ink);background:#f6f9fb}.topbar{height:88px;background:var(--navy);color:#fff;display:flex;align-items:center;justify-content:space-between;padding:0 4vw;position:sticky;top:0;z-index:10}.brand{display:flex;align-items:center;gap:13px;color:#fff;text-decoration:none}.brand-mark{display:grid;place-items:center;width:43px;height:43px;border:1px solid #70b5e9;border-radius:50%;font-size:12px;font-weight:700}.brand strong{font-size:16px;line-height:.83;letter-spacing:.08em}.brand small{display:block;margin-top:8px;color:#80bce8;font-size:9px;letter-spacing:.16em}.progress-wrap{width:min(340px,38vw);font-size:12px;letter-spacing:.06em}.progress-wrap>span{display:block;text-align:right;margin-bottom:8px}.progress{height:4px;background:#34506a;border-radius:9px;overflow:hidden}.progress i{display:block;width:16.67%;height:100%;background:#5cb6f3;transition:width .45s ease}main{min-height:calc(100vh - 128px);display:grid;grid-template-columns:320px 1fr;max-width:1500px;margin:auto;background:#fff;box-shadow:var(--shadow)}.rail{background:var(--ice);padding:56px 40px;border-right:1px solid var(--line)}.eyebrow{color:var(--blue);font-weight:800;font-size:12px;letter-spacing:.14em}.rail h1{font-size:48px;line-height:.94;margin:14px 0 22px;color:var(--navy);letter-spacing:-.04em}.rail-copy{font-size:16px;line-height:1.55;color:#425a70}.rail nav{display:grid;gap:6px;margin:38px 0}.rail nav button{border:0;background:transparent;text-align:left;padding:12px 14px;color:#64778a;border-left:3px solid transparent;cursor:pointer}.rail nav button.active{background:#fff;color:var(--navy);border-left-color:var(--blue);font-weight:700}.duration{font-size:12px;color:#76889a;margin-top:36px}.stage{position:relative;min-width:0;padding-bottom:80px}.lesson{display:none;grid-template-columns:minmax(380px,1fr) minmax(360px,.9fr);min-height:650px;animation:reveal .5s ease}.lesson.active{display:grid}.copy{padding:70px 5vw 44px}.copy.wide{grid-column:1/-1;max-width:950px}.copy h2{font-size:clamp(38px,4vw,64px);line-height:1.02;letter-spacing:-.045em;margin:18px 0 24px;color:var(--navy)}.lead{font-size:20px;line-height:1.55;color:#405a72;max-width:720px}.callout{border-left:4px solid var(--blue);background:var(--ice);padding:20px 22px;margin-top:34px;display:grid;gap:7px}.callout span,.cards span,.metric-grid span{color:#52687b;line-height:1.45}.visual{position:relative;overflow:hidden;background:var(--navy);min-height:500px}.cloud{position:absolute;top:15%;left:25%;width:160px;height:55px;background:#dbeefa;border-radius:40px}.cloud i{position:absolute;border-radius:50%;background:#dbeefa;width:75px;height:75px;top:-35px}.cloud i:nth-child(2){left:55px;width:95px;height:95px;top:-50px}.cloud i:nth-child(3){left:110px}.building{position:absolute;left:15%;bottom:23%;width:180px;height:230px;background:#fff;border-left:12px solid #b8cfdf}.building:before{content:"";position:absolute;left:-35px;top:-50px;border-left:120px solid transparent;border-right:120px solid transparent;border-bottom:60px solid #bccbd7}.building span{position:absolute;bottom:0;right:30px;width:45px;height:85px;background:#8ba9bf}.ground{position:absolute;bottom:15%;left:0;width:100%;height:85px;background:#263f55;clip-path:polygon(0 0,100% 55%,100% 100%,0 100%)}.ground b{position:absolute;right:12%;top:48%;color:#75bff0;font-size:12px;letter-spacing:.14em}.drops i{position:absolute;top:25%;width:3px;height:30px;background:#7fc8f7;animation:rain 1.2s linear infinite}.drops i:nth-child(1){left:15%}.drops i:nth-child(2){left:35%;animation-delay:.2s}.drops i:nth-child(3){left:55%;animation-delay:.4s}.drops i:nth-child(4){left:72%;animation-delay:.7s}.drops i:nth-child(5){left:88%;animation-delay:.9s}.flow i{position:absolute;bottom:20%;left:48%;width:90px;height:3px;background:#41a7e7;transform:rotate(7deg);animation:flow 1.4s ease-in-out infinite}.flow i:nth-child(2){left:63%;animation-delay:.25s}.flow i:nth-child(3){left:78%;animation-delay:.5s}.cards{display:grid;gap:12px;margin-top:30px}.cards div{display:grid;grid-template-columns:45px 140px 1fr;align-items:center;gap:12px;border-top:1px solid var(--line);padding:16px 0}.cards em{font-style:normal;color:var(--blue);font-weight:800}.site-section{position:absolute;inset:15% 8%;background:linear-gradient(#8ca7b7 0 45%,#40566b 45% 100%);border-radius:4px}.house{position:absolute;left:20%;bottom:55%;width:35%;height:28%;background:white}.house:before{content:"";position:absolute;left:-10%;top:-50%;border-left:90px solid transparent;border-right:90px solid transparent;border-bottom:85px solid #d0dde6}.surface-line,.subsoil-line,.pipe-line{position:absolute;left:45%;width:50%;height:5px}.surface-line{top:43%;background:#6dc2f2;transform:rotate(5deg)}.subsoil-line{top:62%;background:#9cd5f2;transform:rotate(2deg)}.pipe-line{top:79%;background:#fff;border-radius:8px;height:17px}.legend{position:absolute;bottom:8%;left:8%;right:8%;display:flex;justify-content:space-between;color:#fff;font-size:11px;letter-spacing:.1em}.metric-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:28px}.metric-grid div{background:var(--ice);padding:18px}.metric-grid strong{display:block;font-size:27px;color:var(--blue);margin-bottom:10px}.note{font-size:14px;line-height:1.5;color:#5d7285}.datum{position:absolute;left:10%;top:20%;height:60%;width:35%;background:white;border-left:10px solid #a8bdcc}.datum span{color:var(--navy);font-weight:800;position:absolute;top:20px;left:20px}.slope{position:absolute;left:38%;right:7%;bottom:25%;height:100px;background:#4b657b;clip-path:polygon(0 0,100% 40%,100% 100%,0 100%)}.slope span{position:absolute;top:55%;left:35%;color:#fff}.slope b{position:absolute;top:10%;right:10%;color:#7fc8f7}.arrow{position:absolute;bottom:42%;left:50%;width:32%;height:4px;background:#64b9ee;transform:rotate(7deg);animation:flow 1.2s infinite}.checklist{list-style:none;padding:0;margin:28px 0}.checklist li{position:relative;padding:12px 0 12px 34px;border-bottom:1px solid var(--line)}.checklist li:before{content:"✓";position:absolute;left:0;color:var(--blue);font-weight:800}.soil{position:absolute;inset:35% 0 0;background:#4f6576}.footing{position:absolute;left:10%;top:20%;width:30%;height:55%;background:#d7e0e7}.aggregate{position:absolute;left:45%;bottom:12%;width:42%;height:35%;background:radial-gradient(circle,#a8bdcc 3px,transparent 4px);background-size:18px 18px}.drain{position:absolute;left:49%;bottom:20%;width:34%;height:45px;background:#eff6fa;border:8px solid #819aaa;border-radius:25px;transform:rotate(3deg)}.water-dots{position:absolute;left:43%;bottom:32%;width:47%;height:25%;background:radial-gradient(circle,#5bb8ec 2px,transparent 3px);background-size:22px 22px;animation:flow 1.5s infinite}.subsoil-visual>span{position:absolute;bottom:8%;left:50%;color:#9bd8f7;font-weight:800;letter-spacing:.12em}.paving{position:absolute;top:15%;left:0;right:0;height:90px;background:#dce6ec;border-bottom:15px solid #849aaa}.paving span{position:absolute;left:8%;top:25px;color:var(--navy);font-size:12px;font-weight:800}.cover-line{position:absolute;top:30%;left:18%;height:37%;border-left:2px dashed #63b8ea}.cover-line b{display:block;color:#8bd0f5;writing-mode:vertical-rl;margin-left:10px;font-size:11px}.pipe{position:absolute;left:32%;right:10%;bottom:23%;height:105px;border:16px solid #cddce5;border-radius:55px;background:#162e44}.pipe i{display:block;width:35%;height:100%;background:#398bc0;animation:pipewater 2s ease-in-out infinite}.discharge{position:absolute;bottom:9%;right:8%;color:#89cef5;font-size:11px;letter-spacing:.1em}.quiz{grid-template-columns:1fr}.quiz form{display:grid;gap:12px;margin:30px 0}.quiz label{display:flex;gap:15px;align-items:center;border:1px solid var(--line);padding:18px;border-radius:4px;cursor:pointer}.quiz label:has(input:checked){border-color:var(--blue);background:var(--ice)}.quiz input{width:20px;height:20px;accent-color:var(--blue)}.quiz button,.controls button{background:var(--navy);color:#fff;border:0;padding:14px 22px;font-weight:700;cursor:pointer}.feedback,.completion{padding:18px 20px;margin-top:18px}.feedback.good,.completion{background:#e8f7f2;color:var(--good)}.feedback.bad{background:#faeded;color:var(--bad)}.completion{display:grid;gap:5px}.controls{position:absolute;bottom:0;left:0;right:0;display:flex;justify-content:space-between;align-items:center;padding:22px 5vw;border-top:1px solid var(--line);background:#fff}.controls button:disabled{opacity:.35}.dots{display:flex;gap:8px}.dots i{width:8px;height:8px;border-radius:50%;background:#c4d1da}.dots i.active{background:var(--blue);transform:scale(1.4)}.disclaimer{max-width:1500px;margin:auto;padding:16px 4vw;font-size:11px;color:#718394;background:#f6f9fb}.controls #prev{background:#dce6ed;color:var(--navy)}@keyframes reveal{from{opacity:0;transform:translateY(12px)}to{opacity:1;transform:none}}@keyframes rain{from{transform:translateY(-60px);opacity:0}to{transform:translateY(200px);opacity:1}}@keyframes flow{0%,100%{opacity:.3;transform:translateX(-12px) rotate(7deg)}50%{opacity:1;transform:translateX(12px) rotate(7deg)}}@keyframes pipewater{0%,100%{width:25%}50%{width:75%}}
@media(max-width:900px){.topbar{height:76px}.progress-wrap{width:38%}main{display:block}.rail{padding:28px 24px}.rail h1{font-size:36px}.rail-copy,.duration{display:none}.rail nav{display:flex;overflow:auto;margin:20px -24px -28px;padding:0 24px}.rail nav button{min-width:max-content;border-left:0;border-bottom:3px solid transparent}.rail nav button.active{border-bottom-color:var(--blue)}.lesson,.lesson.active{grid-template-columns:1fr;min-height:auto}.copy{padding:44px 24px}.copy h2{font-size:40px}.lead{font-size:18px}.visual{min-height:390px}.metric-grid{grid-template-columns:1fr}.cards div{grid-template-columns:38px 110px 1fr}.controls{position:sticky;bottom:0;padding:15px 20px}.disclaimer{padding-bottom:90px}}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}
.quiz form{gap:22px}.quiz fieldset{border:1px solid var(--line);padding:22px;border-radius:6px;display:grid;gap:10px}.quiz fieldset.correct{border-color:#76bca8}.quiz fieldset.incorrect{border-color:#d9a1a1}.quiz legend{font-weight:700;color:var(--navy);padding:0 8px;line-height:1.45}.quiz legend span{color:var(--blue);margin-right:8px}.quiz fieldset label{padding:15px 18px}.question-feedback{margin:5px 0 0;padding:12px 14px;background:#f1f6f9;color:#405a72;font-size:14px;line-height:1.45}.quiz fieldset.correct .question-feedback{background:#e8f7f2;color:var(--good)}.quiz fieldset.incorrect .question-feedback{background:#faeded;color:var(--bad)}.quiz form>button{justify-self:start;font-size:16px}
.beta-feedback{margin-top:42px;border-top:5px solid var(--blue);background:#f3f8fb;padding:30px}.beta-feedback h3{font-size:30px;line-height:1.1;color:var(--navy);margin:8px 0 12px}.beta-feedback>p:not(.eyebrow){color:#52687b;line-height:1.55}.beta-feedback form{margin:24px 0 0}.feedback-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px}.beta-feedback form>label,.feedback-grid label{display:grid;gap:7px;border:0;padding:0;background:transparent}.beta-feedback label>span{font-size:13px;font-weight:700;color:var(--navy)}.beta-feedback input[type="text"],.beta-feedback input[type="email"],.beta-feedback select,.beta-feedback textarea{width:100%;border:1px solid var(--line);background:#fff;color:var(--ink);padding:13px 14px;border-radius:4px;font:inherit}.beta-feedback textarea{resize:vertical}.beta-feedback .consent{display:flex;align-items:flex-start;grid-template-columns:none}.beta-feedback .consent input{margin-top:2px}.form-note{font-size:12px;color:#607387;margin:0;max-width:600px}@media(max-width:650px){.feedback-grid{grid-template-columns:1fr}.beta-feedback{padding:24px 18px}.beta-feedback h3{font-size:26px}}