:root{--ink:#12263a;--muted:#5d6d7e;--line:#dce4ea;--paper:#fff;--soft:#f4f8fb;--excel:#217346;--navy:#173b57;--gold:#f4b942;--danger:#a23b3b;--radius:18px;--shadow:0 12px 34px rgba(19,52,75,.10)}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--soft);color:var(--ink);font:16px/1.65 Inter,Segoe UI,Arial,sans-serif}.skip-link{position:fixed;left:12px;top:-80px;background:#fff;color:#000;padding:10px 14px;z-index:50;border-radius:8px}.skip-link:focus{top:12px}.site-header{height:76px;padding:0 clamp(18px,4vw,64px);display:flex;align-items:center;background:#fff;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:12px;color:var(--ink);text-decoration:none}.brand-mark{display:grid;place-items:center;width:42px;height:42px;border-radius:12px;background:var(--excel);color:#fff;font-weight:800}.brand strong,.brand small{display:block}.brand small{font-size:.76rem;color:var(--muted)}.home-shell{width:min(1180px,92vw);margin:0 auto;padding:60px 0}.home-intro{max-width:850px}.eyebrow{font-weight:800;text-transform:uppercase;letter-spacing:.12em;color:var(--excel);font-size:.8rem}.home-intro h1{font-size:clamp(2.2rem,5vw,4.8rem);line-height:1.02;letter-spacing:-.045em;margin:.18em 0}.home-intro>p:not(.eyebrow){font-size:1.18rem;color:var(--muted);max-width:760px}.flow-strip{display:flex;flex-wrap:wrap;gap:8px;margin:28px 0 38px}.flow-strip span{background:#fff;border:1px solid var(--line);padding:7px 11px;border-radius:999px;font-size:.88rem;font-weight:700}.stage-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.stage-card{display:flex;gap:20px;min-height:190px;padding:26px;border-radius:var(--radius);background:#fff;color:var(--ink);text-decoration:none;border:1px solid var(--line);box-shadow:var(--shadow);transition:.2s transform,.2s border-color}.stage-card:hover,.stage-card:focus-visible{transform:translateY(-3px);border-color:var(--excel)}.stage-number{font-size:2.3rem;font-weight:900;color:var(--excel)}.stage-card p{margin:0;text-transform:uppercase;letter-spacing:.12em;font-size:.75rem;color:var(--muted);font-weight:800}.stage-card h2{margin:7px 0;line-height:1.2}.stage-card div span{color:var(--muted)}.notice{margin-top:24px;background:#eaf6ef;border-left:5px solid var(--excel);padding:18px 20px;border-radius:10px}.site-footer{text-align:center;color:var(--muted);padding:30px}
.course-shell{min-height:100vh;display:grid;grid-template-columns:300px minmax(0,1fr)}.course-nav{position:sticky;top:0;height:100vh;overflow:auto;background:var(--navy);color:#fff;padding:24px 20px}.course-nav .brand{color:#fff;margin-bottom:30px}.course-nav .brand small{color:#bed0dd}.back-home{display:inline-block;color:#d8e7ef;margin-bottom:18px;text-decoration:none;font-size:.9rem}.stage-kicker{font-size:.75rem;text-transform:uppercase;letter-spacing:.13em;color:#a9c4d4}.course-nav h1{font-size:1.55rem;line-height:1.2;margin:7px 0}.stage-summary{font-size:.9rem;color:#c8dae5}.topic-nav{list-style:none;padding:0;margin:26px 0}.topic-nav button{width:100%;display:flex;align-items:flex-start;gap:10px;text-align:left;color:#dceaf2;background:transparent;border:0;border-radius:11px;padding:11px 10px;font:inherit;cursor:pointer}.topic-nav button:hover,.topic-nav button:focus-visible{background:#244e6b}.topic-nav button.active{background:#fff;color:var(--navy);font-weight:700}.topic-code{font-size:.74rem;min-width:28px;font-weight:900;color:var(--gold)}.topic-nav button.active .topic-code{color:var(--excel)}.local-note{font-size:.78rem;color:#abc0ce;border-top:1px solid #365c75;padding-top:16px}.lesson-main{min-width:0}.lesson-toolbar{position:sticky;top:0;z-index:10;display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:62px;padding:10px clamp(18px,4vw,56px);background:rgba(244,248,251,.94);border-bottom:1px solid var(--line);backdrop-filter:blur(10px)}.menu-toggle{display:none}.toolbar-flow{font-size:.84rem;color:var(--muted)}.lesson-wrap{width:min(960px,calc(100% - 40px));margin:0 auto;padding:44px 0 80px}.lesson-head{display:grid;grid-template-columns:1fr auto;gap:24px;align-items:start;margin-bottom:30px}.lesson-label{text-transform:uppercase;font-size:.76rem;letter-spacing:.12em;color:var(--excel);font-weight:900}.lesson-head h2{font-size:clamp(2rem,4vw,3.5rem);line-height:1.05;letter-spacing:-.035em;margin:8px 0 14px}.lesson-head p{font-size:1.08rem;color:var(--muted);max-width:720px}.lesson-badge{border:1px solid var(--line);background:#fff;border-radius:14px;padding:12px 14px;font-size:.82rem;white-space:nowrap}.lesson-section{margin:20px 0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);box-shadow:0 5px 18px rgba(19,52,75,.05);overflow:hidden}.section-head{display:flex;align-items:center;gap:12px;padding:19px 22px;border-bottom:1px solid var(--line)}.step-no{display:grid;place-items:center;width:31px;height:31px;border-radius:9px;background:#e7f4ec;color:var(--excel);font-weight:900}.section-head h3{margin:0;font-size:1.14rem}.section-body{padding:22px}.case-box{border-left:4px solid var(--gold);padding:4px 0 4px 18px}.case-box strong{display:block;margin-bottom:4px}.data-table{width:100%;border-collapse:collapse;margin:14px 0}.data-table th{background:#eaf2f6;text-align:left}.data-table th,.data-table td{padding:10px 12px;border-bottom:1px solid var(--line)}.steps{padding-left:22px}.steps li{margin:.6em 0}.formula{display:block;background:#102c40;color:#eaf6ef;border-radius:12px;padding:15px 17px;overflow:auto;white-space:pre-wrap;font:14px/1.55 Consolas,monospace}.try-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}.field{display:flex;flex-direction:column;gap:5px}.field label{font-weight:700;font-size:.9rem}.field input,.field select{width:100%;padding:10px 12px;border:1px solid #aebdc8;border-radius:9px;background:#fff;color:var(--ink);font:inherit}.field input:focus,.field select:focus{outline:3px solid rgba(33,115,70,.18);border-color:var(--excel)}.live-result{grid-column:1/-1;background:#edf7f1;border:1px solid #b9dac7;padding:16px;border-radius:12px}.live-result strong{font-size:1.25rem;color:#185c37}.download-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.download-card{display:block;border:1px solid var(--line);border-radius:13px;padding:16px;color:var(--ink);text-decoration:none}.download-card:hover,.download-card:focus-visible{border-color:var(--excel);background:#f3faf6}.download-card strong,.download-card span{display:block}.download-card span{font-size:.86rem;color:var(--muted)}.check-list{list-style:none;padding:0}.check-list li{display:flex;gap:9px;margin:9px 0}.check-list li::before{content:'✓';color:var(--excel);font-weight:900}.reveal{border:0;background:var(--navy);color:#fff;padding:10px 14px;border-radius:9px;font-weight:800;cursor:pointer}.answer-box{display:none;margin-top:14px;padding:15px;border-radius:10px;background:#fff8e8;border:1px solid #efd38c}.answer-box.visible{display:block}.challenge{background:#122f43;color:#fff}.challenge .section-head{border-color:#35536a}.challenge .step-no{background:var(--gold);color:#172b3a}.challenge .section-body p{color:#deebf3}.completion{display:flex;align-items:flex-start;gap:10px;background:#eaf6ef;border:1px solid #b9dac7;padding:16px;border-radius:12px;margin-top:22px}.completion input{width:20px;height:20px;margin-top:3px}.lesson-pager{display:flex;justify-content:space-between;gap:12px;margin-top:28px}.pager-btn{border:1px solid var(--line);background:#fff;border-radius:10px;padding:10px 14px;color:var(--ink);font-weight:750;cursor:pointer}.pager-btn:disabled{opacity:.4;cursor:not-allowed}.status-message{min-height:1.3em;color:var(--excel);font-weight:700}
@media(max-width:850px){.stage-grid{grid-template-columns:1fr}.course-shell{display:block}.course-nav{position:fixed;z-index:30;left:0;top:0;width:min(310px,88vw);transform:translateX(-102%);transition:.2s transform}.course-nav.open{transform:translateX(0);box-shadow:0 0 0 100vmax rgba(0,0,0,.35)}.menu-toggle{display:inline-flex;border:1px solid var(--line);background:#fff;padding:8px 11px;border-radius:9px;font-weight:800}.toolbar-flow{font-size:.74rem}.lesson-wrap{width:min(100% - 28px,960px);padding-top:28px}.lesson-head{grid-template-columns:1fr}.lesson-badge{justify-self:start}.try-grid,.download-grid{grid-template-columns:1fr}.live-result{grid-column:auto}}
@media(max-width:520px){.home-shell{padding-top:36px}.stage-card{padding:20px;min-height:0}.stage-number{font-size:1.8rem}.lesson-toolbar{padding-inline:14px}.toolbar-flow{display:none}.section-body,.section-head{padding:17px}.data-table{font-size:.86rem;display:block;overflow:auto}.lesson-pager{flex-direction:column}.pager-btn{width:100%}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}