:root{--ink:#1d2d27;--muted:#66756e;--line:#dce5df;--paper:#f6f8f5;--white:#fff;--green:#146c52;--green-dark:#0c4938;--green-soft:#e3f3eb;--gold:#e2b768;--red:#a83b3e;--shadow:0 12px 32px rgba(23,52,40,.07);font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--paper);color:var(--ink);font-size:15px;line-height:1.6}.topbar{height:78px;padding:0 32px;background:#fff;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:24px;position:sticky;top:0;z-index:10}.brand{display:flex;align-items:center;gap:12px;color:var(--ink);text-decoration:none;font-size:17px;font-weight:650;line-height:1.1}.brand b{color:var(--green)}.brand small{display:block;margin-top:7px;font-size:9px;letter-spacing:1.6px;color:#7a8982;font-weight:800}.brand-mark{width:42px;height:42px;display:grid;place-items:center;border-radius:13px;background:var(--green);color:#fff;font-family:ui-monospace,monospace;font-size:18px;font-weight:800}.top-actions{display:flex;align-items:center;gap:16px}.save-note{font-size:12px;color:var(--muted);display:flex;align-items:center;gap:8px}.save-dot{width:7px;height:7px;border-radius:50%;background:#21a26e}.button{border:1px solid transparent;border-radius:9px;padding:10px 14px;font:inherit;font-size:12px;font-weight:750;cursor:pointer;transition:transform .15s,background .15s}.button:hover{transform:translateY(-1px)}.button-quiet{background:#fff;border-color:var(--line);color:var(--muted)}.button-primary{background:var(--green);color:#fff}.button-primary:hover{background:var(--green-dark)}.button-outline{background:white;border-color:#cddbd2;color:var(--green)}.button:focus-visible,.chapter-link:focus-visible,.search-input:focus-visible,textarea:focus-visible{outline:3px solid #91d5b6;outline-offset:2px}.app-shell{display:grid;grid-template-columns:288px minmax(0,1fr);min-height:calc(100vh - 122px)}.sidebar{background:#fff;border-right:1px solid var(--line);padding:27px 17px 24px;display:flex;flex-direction:column;min-width:0}.course-heading{padding:0 10px 18px}.eyebrow{font-size:10px;font-weight:850;color:var(--green);letter-spacing:1.5px}.course-heading h2{font-size:23px;margin:4px 0 3px;letter-spacing:-.6px}.course-heading p{font-size:12px;color:var(--muted);margin:0;line-height:1.5}.progress-block{padding:15px 10px 19px;border-top:1px solid #edf1ee;border-bottom:1px solid #edf1ee}.progress-label{display:flex;justify-content:space-between;align-items:center;font-size:11px;color:var(--muted);margin-bottom:9px}.progress-label strong{font-size:11px;color:var(--green)}.progress-track{height:6px;background:#edf1ee;border-radius:10px;overflow:hidden}.progress-fill{width:0%;height:100%;background:linear-gradient(90deg,#146c52,#56b78c);border-radius:10px;transition:width .25s}.search-label{font-size:9px;letter-spacing:1.4px;font-weight:850;color:#87958e;margin:19px 10px 7px}.search-input{width:100%;border:1px solid var(--line);background:#fbfcfb;border-radius:9px;padding:11px 12px;font:inherit;font-size:12px;outline:0;color:var(--ink)}.chapter-nav{display:grid;gap:3px;margin-top:15px}.chapter-link{display:grid;grid-template-columns:28px 1fr 15px;align-items:center;gap:8px;text-align:left;border:0;border-radius:9px;padding:9px 9px;background:transparent;cursor:pointer;color:#52625a;font:inherit;min-width:0}.chapter-link:hover{background:#f5f8f6}.chapter-link.active{background:var(--green-soft);color:var(--green-dark);font-weight:750}.chapter-num{display:grid;place-items:center;width:26px;height:26px;border:1px solid #e1e9e4;border-radius:7px;background:white;color:#77857e;font-size:10px;font-weight:800}.chapter-link.active .chapter-num{background:var(--green);border-color:var(--green);color:white}.chapter-link .chapter-name{font-size:11px;line-height:1.35}.chapter-check{font-size:12px;color:#29946b}.sidebar-foot{margin-top:auto;border-top:1px solid #edf1ee;padding:17px 10px 0}.mini-badge{display:inline-block;font-size:9px;letter-spacing:.8px;font-weight:850;color:var(--green);background:var(--green-soft);padding:5px 8px;border-radius:5px}.sidebar-foot p{font-size:11px;color:var(--muted);margin:9px 0 0;line-height:1.5}.main-content{padding:34px clamp(22px,4.5vw,68px) 70px;min-width:0;max-width:1600px;width:100%;margin:0 auto}.welcome-strip{background:linear-gradient(115deg,#103f33,#146c52);color:#fff;border-radius:18px;padding:29px 34px;display:flex;justify-content:space-between;gap:20px;align-items:center;overflow:hidden;position:relative;margin-bottom:28px;box-shadow:var(--shadow)}.welcome-strip:after{content:"";position:absolute;right:80px;top:-130px;width:250px;height:250px;border:1px solid rgba(255,255,255,.12);border-radius:50%;box-shadow:0 0 0 25px rgba(255,255,255,.035),0 0 0 50px rgba(255,255,255,.025)}.welcome-strip .eyebrow{color:#b5e2cc}.welcome-strip h1{font-size:clamp(24px,3vw,34px);line-height:1.16;letter-spacing:-1.3px;margin:8px 0 8px;max-width:650px}.welcome-strip h1 em{font-style:normal;color:#ffdb8a}.welcome-strip p{color:#d5e7dd;margin:0;font-size:13px}.welcome-icon{display:flex;align-items:center;gap:4px;font-size:49px;font-weight:800;letter-spacing:-5px;transform:rotate(-7deg);z-index:1;color:#ffdb8a;padding-right:10px}.welcome-icon span:nth-child(2){color:#a9dcc4}.lesson-header{display:flex;align-items:flex-start;justify-content:space-between;gap:22px;margin:4px 0 20px}.lesson-index{font-size:11px;color:var(--green);letter-spacing:1.5px;font-weight:850}.lesson-title{font-size:clamp(25px,3vw,37px);line-height:1.16;letter-spacing:-1.1px;margin:6px 0 10px;max-width:850px}.lesson-intro{font-size:15px;color:var(--muted);max-width:880px;margin:0}.lesson-actions{display:flex;gap:7px;flex-shrink:0;flex-wrap:wrap;justify-content:flex-end}.lesson-layout{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(275px,.8fr);gap:18px;align-items:start}.lesson-left,.lesson-right{display:grid;gap:16px;min-width:0}.panel{background:#fff;border:1px solid var(--line);border-radius:14px;padding:22px;box-shadow:0 5px 17px rgba(23,52,40,.025);min-width:0}.panel-top{display:flex;align-items:center;gap:10px;margin-bottom:14px}.panel-icon{width:32px;height:32px;display:grid;place-items:center;border-radius:9px;background:var(--green-soft);color:var(--green);font-weight:850;font-size:14px}.panel h3{font-size:15px;letter-spacing:-.2px;margin:0}.panel-subtitle{font-size:11px;color:var(--muted);margin:-7px 0 13px}.concept-list{display:grid;gap:14px}.concept{display:grid;grid-template-columns:122px 1fr;gap:14px;padding-bottom:13px;border-bottom:1px solid #edf1ee}.concept:last-child{padding-bottom:0;border:0}.concept strong{font-size:12px;color:var(--green-dark)}.concept p{font-size:12px;color:#65736c;margin:0;line-height:1.62}.concept code,.lesson-copy code{background:#eef4f0;padding:2px 5px;border-radius:4px;font-size:.93em;color:#145b46}.terms{display:flex;flex-wrap:wrap;gap:6px}.term{font-size:10px;font-weight:750;color:#53635a;border:1px solid #dfe8e2;background:#f8faf8;padding:5px 8px;border-radius:6px}.key-note{background:#fff8e8;border-color:#f2e2b9}.key-note .panel-icon{background:#ffedbf;color:#8a5b0b}.key-note p{margin:0;font-size:12px;color:#63553a}.practice-panel{background:#f0f8f3;border-color:#d6eadf}.practice-panel .panel-icon{background:#d7efe1}.practice-panel p{font-size:13px;line-height:1.6;margin:0 0 13px;color:#3d5b4b}.quiz-answer{display:none;background:#f5f8f6;border:1px dashed #ccdcd1;border-radius:8px;padding:11px 12px;color:#355847;font-size:12px;margin-top:12px}.quiz-answer.show{display:block}.question{font-size:13px;font-weight:750;margin:0 0 11px}.code-intro{font-size:12px;color:var(--muted);margin:0 0 13px}.code-block{margin:0;background:#15231e;color:#ddf5e8;border-radius:9px;padding:14px 15px;overflow:auto;font-family:ui-monospace,SFMono-Regular,Consolas,monospace;font-size:11px;line-height:1.7;white-space:pre;max-height:280px}.code-toolbar{display:flex;align-items:center;justify-content:space-between;gap:10px;margin:0 0 9px}.code-tag{font-size:9px;letter-spacing:1px;font-weight:850;color:#89988f}.load-example{font-size:10px;padding:7px 9px}.playground{margin-top:27px}.section-heading{display:flex;align-items:flex-end;justify-content:space-between;gap:20px;margin-bottom:15px}.section-heading h2{font-size:24px;letter-spacing:-.8px;margin:4px 0}.section-heading p{font-size:12px;color:var(--muted);margin:0}.playground-card{background:#fff;border:1px solid var(--line);border-radius:14px;overflow:hidden;box-shadow:var(--shadow)}.playground-head{background:#fdfefd;padding:13px 18px;display:flex;justify-content:space-between;gap:12px;align-items:center;border-bottom:1px solid var(--line)}.playground-head strong{font-size:13px}.playground-head span{font-size:10px;color:var(--muted)}.playground-actions{display:flex;gap:7px;flex-wrap:wrap}.editor-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:0}.editor-pane{min-width:0;border-right:1px solid var(--line)}.editor-pane:last-child{border-right:0}.editor-label{display:flex;justify-content:space-between;align-items:center;padding:10px 12px;background:#f6f8f6;border-bottom:1px solid var(--line);font-size:10px;font-weight:850;letter-spacing:.6px}.editor-label span{color:var(--muted);font-size:9px;letter-spacing:0;font-weight:500}.code-editor{display:block;resize:vertical;width:100%;min-height:220px;padding:13px;border:0;border-radius:0;outline:0;background:#172620;color:#d7eee2;font:11px/1.7 ui-monospace,SFMono-Regular,Consolas,monospace;tab-size:2}.preview-wrap{padding:17px;background:#f6f8f5;border-top:1px solid var(--line)}.preview-top{display:flex;justify-content:space-between;align-items:center;margin-bottom:10px}.preview-top strong{font-size:12px}.preview-top span{font-size:10px;color:var(--muted)}#previewFrame{width:100%;height:260px;border:1px solid #d9e3dc;border-radius:10px;background:white;display:block}.practice-list{margin:0;padding-left:19px;color:#53645b;font-size:12px}.practice-list li{margin:6px 0}.bottom-nav{display:flex;justify-content:space-between;gap:12px;margin-top:23px;padding-top:17px;border-top:1px solid var(--line)}.bottom-nav button{max-width:48%}.page-footer{min-height:44px;background:#fff;border-top:1px solid var(--line);display:flex;justify-content:space-between;gap:15px;align-items:center;padding:12px 32px;font-size:10px;color:#7a8981}.empty-state{padding:26px;text-align:center;color:var(--muted);background:white;border:1px solid var(--line);border-radius:12px}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}
@media(max-width:1100px){.app-shell{grid-template-columns:246px minmax(0,1fr)}.lesson-layout{grid-template-columns:1fr}.lesson-right{grid-template-columns:repeat(2,minmax(0,1fr));align-items:start}.lesson-right .panel:first-child{grid-column:1/-1}.main-content{padding:27px 25px 55px}.concept{grid-template-columns:110px 1fr}}
@media(max-width:760px){.topbar{height:auto;min-height:68px;padding:12px 16px}.save-note{display:none}.brand-mark{width:36px;height:36px}.app-shell{grid-template-columns:1fr}.sidebar{border-right:0;border-bottom:1px solid var(--line);padding:16px}.course-heading{padding:0 2px 12px}.course-heading h2{font-size:19px}.course-heading p{display:none}.progress-block{padding:12px 2px}.search-label{margin:13px 2px 6px}.chapter-nav{grid-template-columns:repeat(2,minmax(0,1fr));max-height:280px;overflow:auto;padding-right:2px}.chapter-link{grid-template-columns:25px 1fr 12px;padding:7px 6px}.chapter-link .chapter-name{font-size:10px}.chapter-num{width:23px;height:23px}.sidebar-foot{display:none}.main-content{padding:20px 14px 44px}.welcome-strip{padding:22px 20px;margin-bottom:22px}.welcome-icon{display:none}.welcome-strip h1{font-size:26px}.lesson-header{display:block}.lesson-actions{justify-content:flex-start;margin-top:14px}.lesson-title{font-size:28px}.panel{padding:17px}.lesson-right{grid-template-columns:1fr}.lesson-right .panel:first-child{grid-column:auto}.concept{grid-template-columns:95px 1fr;gap:10px}.editor-grid{grid-template-columns:1fr}.editor-pane{border-right:0;border-bottom:1px solid var(--line)}.code-editor{min-height:140px}.playground-head{align-items:flex-start;flex-direction:column}.section-heading{display:block}.section-heading h2{font-size:22px}.section-heading>div:last-child{margin-top:9px}.page-footer{padding:12px 16px;flex-direction:column;align-items:flex-start;gap:3px}}