*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:#f4f7fa;color:#182b42;font:15px/1.68 system-ui,"Malgun Gothic",sans-serif}a{color:inherit}button,select{font:inherit}button{cursor:pointer}button:focus-visible,a:focus-visible,select:focus-visible{outline:3px solid #4b91ee;outline-offset:3px}.topbar{background:#10273e;color:white}.top-inner{max-width:1350px;margin:auto;min-height:69px;display:flex;align-items:center;justify-content:space-between;gap:14px;padding:10px 20px}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;font-weight:900;font-size:17px}.logomark{background:#4778e5;color:white;width:38px;height:38px;border-radius:11px;display:grid;place-items:center;font-size:21px}.brand small{display:block;font-size:10px;letter-spacing:.17em;color:#92b6e5;font-weight:600}.toplinks{display:flex;gap:16px;flex-wrap:wrap}.toplinks a{color:#c5d6e7;font-size:12px;text-decoration:none;font-weight:700}.toplinks a:hover{color:white}.pagewrap{max-width:1350px;margin:auto}.hero{margin:26px 20px 16px;padding:41px 43px;background:linear-gradient(115deg,#112c51,#183e68);color:white;border-radius:17px;display:grid;grid-template-columns:minmax(0,1.65fr) minmax(250px,.95fr);gap:26px}.eyebrow{font-size:11px;color:#83bafa;letter-spacing:.2em;font-weight:800}.hero h1{font-size:clamp(31px,3.2vw,50px);letter-spacing:-.055em;line-height:1.25;margin:13px 0 19px}.hero h1 em{font-style:normal;color:#90bfff}.hero p{max-width:750px;color:#d9e7fa;line-height:1.85}.hero-actions{display:flex;flex-wrap:wrap;gap:10px;margin:24px 0 18px}.hero-actions a,.finish-links a{padding:11px 16px;border-radius:8px;border:1px solid #ffffff6b;text-decoration:none;font-weight:800;font-size:13px}.hero-actions .primary{background:#4880e9;color:white;border-color:#4880e9}.chip-row{display:flex;gap:8px;flex-wrap:wrap}.chip-row span{font-size:11px;padding:4px 9px;border:1px solid #6f8cac6a;border-radius:20px;color:#c6dff8}.hero-map{border:1px solid #6783a680;padding:21px;border-radius:12px;align-self:center;background:#112e4ba8}.hero-map small{color:#9ac5ff;letter-spacing:.13em}.hero-map div{display:flex;align-items:center;gap:16px;padding:10px 0;border-bottom:1px solid #ffffff2b}.hero-map div:last-child{border:0}.hero-map b{color:#90bfff;min-width:44px}.hero-map span{font-size:13px}.notice{margin:0 20px 18px;background:#fff7ea;border:1px solid #f1d5a0;border-radius:11px;padding:14px 18px;color:#6b4921;font-size:13px}.notice a{font-weight:800}.main-layout{display:grid;grid-template-columns:265px minmax(0,1fr);gap:18px;align-items:start;margin:0 20px 45px}.rail{background:white;border:1px solid #e0e8f0;border-radius:12px;overflow:hidden;position:sticky;top:13px;max-height:calc(100vh - 22px);overflow-y:auto}.rail-heading{padding:19px 17px 14px;border-bottom:1px solid #e9eff5}.rail small{font-size:11px;color:#71839a}.rail-heading h2{font-size:19px;letter-spacing:-.045em;margin:7px 0}.rail-heading p{font-size:12px;color:#6e7e91}.progress{background:#f1f6fb;border-radius:9px;padding:10px}.progress-top{display:flex;justify-content:space-between;font-size:12px;gap:5px}.progress-line{background:#d8e6f3;height:6px;border-radius:9px;margin:9px 0}.progress-line span{display:block;width:0;height:100%;background:#477ee9;border-radius:9px;transition:width .25s}#stepNav{padding:7px}.step-link{display:flex;align-items:center;gap:8px;text-align:left;border:0;background:transparent;width:100%;padding:9px 8px;color:#354d66;border-radius:8px}.step-link:hover{background:#eff6ff}.step-link.is-active{background:#e8f2ff;color:#1756b2;font-weight:800}.step-link .number{font-size:10px;background:#e8edf4;border-radius:5px;padding:3px 5px;min-width:33px;text-align:center}.step-link.done .number{background:#dcf4e9;color:#21724b}.step-link span:last-child{font-size:12px;line-height:1.4}.rail-bottom{display:block;margin:12px;color:#205fae;font-weight:800;font-size:12px}.classroom{min-width:0}.mobile-select{display:none}.lesson-heading{background:white;border:1px solid #dee7ef;border-radius:12px;padding:23px 26px;margin-bottom:14px}.lesson-heading>span{color:#3974c3;font-size:12px;letter-spacing:.12em;font-weight:850}.lesson-heading h2{font-size:clamp(23px,2.1vw,30px);letter-spacing:-.055em;margin:8px 0}.lesson-heading p{margin:0 0 13px;color:#586f88}.chips{display:flex;flex-wrap:wrap;gap:6px}.chips span{background:#edf3fb;color:#476c94;padding:4px 9px;font-size:11px;border-radius:15px}.panel{background:white;border:1px solid #dee7ef;border-radius:12px;padding:23px 25px;margin-bottom:15px;min-width:0}.panel h3{font-size:17px;margin:0 0 14px;letter-spacing:-.035em}.section-head{display:flex;justify-content:space-between;align-items:start;gap:10px;flex-wrap:wrap}.section-head>span{font-size:12px;color:#637f9e}.task-note{background:#e9f4ff;padding:12px 14px;border-radius:8px;color:#245b87;font-size:13px;margin-bottom:18px}.action-guide{font-size:12px;color:#385f87;background:#f2f8ff;padding:10px 12px;border-left:3px solid #75a8e3;border-radius:5px}.op-block{margin:20px 0}.op-title{font-weight:800;display:flex;align-items:center;gap:10px;flex-wrap:wrap}.file-pill{background:#173c69;color:white;border-radius:6px;font-size:12px;font-weight:750;padding:5px 9px}.op-marker{color:#647992;font-size:12px;margin:5px 0 10px}.codewrap{position:relative}.codewrap pre{background:#10253e;color:#d8eafa;font:12px/1.75 Consolas,Monaco,monospace;white-space:pre;tab-size:2;overflow:auto;padding:19px;border-radius:9px;max-height:410px}.copybtn{position:absolute;right:12px;top:10px;border:1px solid #6a8aaf;background:#23466b;color:white;padding:6px 10px;border-radius:6px;font-size:12px}.two-panels{display:grid;grid-template-columns:1fr 1fr;gap:15px}.why-list,.errors-list{display:grid;gap:12px}.why,.error{border:1px solid #e3eaf2;border-radius:8px;padding:12px}.why code{font-size:12px;font-weight:800;color:#205c9a;word-break:break-word}.why p,.error p{margin:4px 0;color:#596f86;font-size:13px}.error strong{color:#93521a;font-size:13px}.error small{font-size:12px;color:#77889b}.device-pick{display:flex;flex-wrap:wrap;gap:5px}.device-pick button{border:1px solid #cfdcea;background:white;padding:6px 10px;border-radius:6px;font-size:12px}.device-pick button.is-on{background:#346cdf;color:white;border-color:#346cdf}.muted{font-size:12px;color:#6a7e92}.preview-scroller{overflow-x:auto;background:repeating-linear-gradient(45deg,#f0f5fa,#f0f5fa 12px,#eaf1f8 12px,#eaf1f8 24px);border:1px solid #d6e3f0;border-radius:9px;padding:16px;min-height:350px}.preview-wrap{margin:0 auto;background:white;border:1px solid #c6d1e0;box-shadow:0 8px 28px #0c29431d;max-width:none}.preview-wrap iframe{border:0;display:block;width:100%;height:450px}.preview-links{display:flex;gap:9px;flex-wrap:wrap;margin-top:11px}.preview-links a{font-size:12px;color:#2164bc;text-decoration:none;border:1px solid #b7cfe9;padding:6px 10px;border-radius:6px}.try{background:#edf8f3;padding:13px 14px;border-left:4px solid #3b9772;border-radius:6px;font-size:13px}.checklist{display:grid;gap:9px}.checkitem{display:flex;align-items:start;gap:10px;padding:9px 10px;border:1px solid #e4ebf4;border-radius:7px;font-size:13px}.checkitem input{margin-top:3px;accent-color:#3974d5}.navigation{display:flex;justify-content:space-between;gap:10px;margin-top:22px}.navigation button{background:white;border:1px solid #c9d7e6;border-radius:8px;padding:10px 17px;color:#24466f}.navigation .primary{background:#366cdd;color:white;border-color:#366cdd}.finish-course{background:#142f51;color:white;border-radius:12px;padding:24px}.finish-course h2{font-size:21px}.finish-course p{color:#cadef4}.finish-links{display:flex;gap:9px;flex-wrap:wrap}.finish-links a{font-size:12px}.footer{text-align:center;color:#617a93;font-size:12px;padding:20px}.preview-scroller a{color:#185c9a}@media(max-width:1020px){.hero{grid-template-columns:1fr}.main-layout{grid-template-columns:235px minmax(0,1fr)}.two-panels{grid-template-columns:1fr}.toplinks{gap:8px}}@media(max-width:760px){.top-inner{align-items:start;flex-direction:column}.hero{margin:13px 12px;padding:27px 20px;gap:18px}.hero-map{padding:13px}.notice{margin:0 12px 13px}.main-layout{margin:0 12px 30px;display:block}.rail{display:none}.mobile-select{display:grid;gap:5px;margin-bottom:11px}.mobile-select label{font-weight:750;font-size:12px}.mobile-select select{padding:11px;border:1px solid #b9cfe5;border-radius:8px;background:white;max-width:100%}.panel{padding:17px 14px}.lesson-heading{padding:19px 15px}.preview-scroller{padding:8px}.codewrap pre{font-size:11px;max-height:350px}.toplinks a{font-size:11px}.device-pick button{padding:5px 7px}}@media print{.topbar,.hero-actions,.notice,.rail,.navigation,.mobile-select,.device-pick,.copybtn,.footer{display:none!important}.main-layout{display:block}.panel,.lesson-heading{break-inside:avoid;border:1px solid #ccc}.hero{margin:0;background:white;color:black;padding:10px}.hero h1{font-size:23px}.hero-map{display:none}.two-panels{display:block}}