:root{color-scheme:dark;--bg:#0c111b;--panel:#121a27;--panel2:#172231;--line:#263344;--text:#e9eef5;--muted:#91a1b6;--accent:#84e6bf;--purple:#b6a2f4;--blue:#8ab9ed;--red:#f3a0a0;--radius:14px;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font-size:14px;line-height:1.65}a{color:var(--accent);text-decoration:none}a:hover{color:#c0ffe2}button,input,textarea,select{font:inherit}button,a,input,textarea,select{outline-offset:4px}button{cursor:pointer}h1,h2,h3,p{margin-top:0}h1{font-size:40px;line-height:1.15;letter-spacing:-1.5px;margin-bottom:16px;font-weight:650}h2{font-size:24px;line-height:1.4;letter-spacing:-.6px;font-weight:600}h3{font-size:19px;line-height:1.4;font-weight:600}p{color:#b7c4d3}code,pre,textarea{font-family:"Cascadia Code","SFMono-Regular",Consolas,monospace}code{color:var(--accent)}small{font-size:12px}hr{border:0;border-top:1px solid var(--line);margin:24px 0}.muted{color:var(--muted)}.accent{color:var(--accent)}.shell{max-width:1380px;margin:0 auto;padding:44px 48px 72px;min-height:calc(100vh - 170px)}.site-header{min-height:82px;border-bottom:1px solid var(--line);display:flex;align-items:center;gap:48px;padding:15px 4%;background:#0e1520}.brand{display:flex;align-items:center;gap:10px;font-size:21px;font-weight:700;color:var(--text);letter-spacing:-.6px;white-space:nowrap}.brand-icon{width:34px;height:34px;background:var(--accent);color:#10231c;display:grid;place-items:center;font-size:32px;border-radius:9px}.brand-tag{font-size:9px;letter-spacing:1px;font-weight:600;border:1px solid #364152;color:var(--muted);border-radius:4px;padding:1px 5px;margin-left:3px}.site-header nav{display:flex;gap:28px;flex:1}.site-header nav a,.account-nav>a:not(.button){color:#aebacc;font-size:13px}.site-header nav a:hover,.site-header nav a[aria-current]{color:var(--accent)}.account-nav{display:flex;align-items:center;gap:18px}.account-nav form{margin:0}.avatar{width:32px;height:32px;display:grid;place-items:center;background:#233e39;border-radius:50%;color:var(--accent)!important}.button{display:inline-flex;align-items:center;justify-content:center;gap:25px;min-height:46px;border:1px solid transparent;background:var(--accent);color:#112a22;padding:10px 21px;border-radius:7px;font-weight:650;font-size:13px;transition:background .15s,transform .15s}.button:hover{background:#a9f5d7;color:#0a2018;transform:translateY(-1px)}.button:disabled{opacity:.6;cursor:wait}.button.secondary{color:var(--text);border-color:#344155;background:#17212e}.button.secondary:hover{background:#233143}.button.small{min-height:37px;padding:6px 13px;gap:16px}.button.full{width:100%}.text-button{border:0;background:transparent;color:var(--muted);padding:8px 0;font-size:12px}.text-button:hover{color:var(--text)}.eyebrow{font-size:10px;font-weight:650;letter-spacing:1.8px;color:var(--accent);display:flex;align-items:center;gap:9px}.status-dot{display:inline-block;width:6px;height:6px;background:var(--accent);border-radius:50%}.hero{display:grid;grid-template-columns:1.07fr 1fr;gap:70px;align-items:center;padding:52px 0 70px}.hero h1{font-size:clamp(40px,4.2vw,61px);line-height:1.1;letter-spacing:-2.6px;margin:25px 0}.hero h1 span{color:var(--accent)}.hero-copy>p{font-size:16px;line-height:1.8;max-width:495px;color:#9eafc2}.actions{display:flex;gap:12px;margin-top:30px;flex-wrap:wrap}.hero-notes{display:flex;flex-wrap:wrap;gap:16px;margin-top:26px;font-size:10px;color:var(--muted)}.hero-notes span:before{content:'✓ ';color:var(--accent)}.hero-lab{border:1px solid #334256;border-radius:16px;overflow:hidden;background:#121c29;box-shadow:0 22px 80px #0003;position:relative}.panel-top{padding:14px 20px;border-bottom:1px solid var(--line);display:flex;justify-content:space-between;gap:10px;font-size:9px;letter-spacing:1px;color:var(--muted)}.panel-top .status-dot{margin-right:7px}.lab-body{padding:27px 24px}.lab-body h3{font-size:22px;margin-top:12px;font-weight:500}.lab-body .waveform{margin:15px -12px 23px}.lab-footer{display:flex;justify-content:space-between;border-top:1px solid var(--line);padding:12px 20px;font-size:8px;color:#75869e;letter-spacing:1px}.mini-editor{padding:18px 22px;background:#0c1420;border:1px solid #2a384b;border-radius:8px;font:12px/1.8 Consolas,monospace}.mini-editor>*{display:block}.mini-editor>code{font-size:19px;margin:9px 0 9px 25px;color:#dfe7f4}.mini-editor b{color:var(--purple);font-weight:400}.mini-editor em{color:var(--accent);font-style:normal}.verified{display:flex;gap:12px;align-items:center;margin-top:23px}.verified>span{color:var(--accent);border-radius:50%;background:#25453c;width:27px;height:27px;text-align:center}.verified strong{font-size:12px;color:#cfdfd7;font-weight:500}.verified small{display:block;color:var(--muted);font-size:10px}.intro-strip{display:flex;gap:32px;border-top:1px solid var(--line);border-bottom:1px solid var(--line);padding:26px 0;align-items:center}.intro-strip>span{font-size:9px;letter-spacing:1.5px;color:var(--accent);white-space:nowrap}.intro-strip p{margin:0;font-size:18px;letter-spacing:-.3px}.feature-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:45px;padding:48px 0}.step-number{font:10px Consolas,monospace;letter-spacing:1px;color:var(--muted)}.feature-grid h3{margin-top:15px}.feature-grid p{font-size:13px;max-width:330px;color:var(--muted)}.course-promo{padding:32px;background:linear-gradient(115deg,#192f30,#17212f);border:1px solid #2c4148;border-radius:12px;display:flex;align-items:center;justify-content:space-between}.course-promo h2{margin:9px 0}.course-promo p{margin:0;color:var(--muted);font-size:12px}.site-footer{border-top:1px solid var(--line);padding:22px 4%;display:flex;justify-content:space-between;font-size:11px;color:#75859b}.page-heading{display:flex;justify-content:space-between;align-items:center;gap:20px;margin:10px 0 32px}.page-heading h1{margin-top:14px}.page-heading p{margin-bottom:0;color:var(--muted)}.layout-sidebar{display:grid;grid-template-columns:minmax(0,1fr) 260px;gap:28px}.panel{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:28px}.sidebar-note{padding:23px;margin-bottom:20px}.sidebar-note h3{margin-top:17px}.sidebar-note p{font-size:12px;color:var(--muted)}.sidebar-note a{font-size:12px}.pill{display:inline-flex;align-items:center;border-radius:5px;border:1px solid #344154;padding:4px 9px;font-size:9px;color:#acb9ca;letter-spacing:.7px;font-weight:600}.pill.success{color:var(--accent);background:#19382f;border-color:#2e5748}.course-header{display:flex;justify-content:space-between;gap:20px;background:linear-gradient(120deg,#182b31,#16202f)}.course-header h2{margin:14px 0 6px}.course-header p{font-size:12px;max-width:510px;margin:0}.course-count{min-width:130px;text-align:right;align-self:center}.course-count strong{font-size:36px;display:block;line-height:1.4;color:var(--accent);font-weight:500}.course-count strong span{font-size:20px;color:#64778b}.course-count small{font-size:8px;letter-spacing:1px;color:#9aacbe}.chapter{margin:38px 0}.chapter-heading{display:flex;gap:16px;align-items:center;margin-bottom:19px}.chapter-heading h2{font-size:21px;margin:0}.chapter-heading p{font-size:12px;color:var(--muted);margin:3px 0 0}.chapter-number{width:36px;height:36px;display:grid;place-items:center;border:1px solid #365047;color:var(--accent);font:13px Consolas,monospace;border-radius:10px}.level-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:15px}.level-card{background:var(--panel);border:1px solid var(--line);padding:20px;border-radius:12px}.level-card.available{border-color:#496c60;background:#16272a}.card-top{display:flex;align-items:center;gap:10px;color:var(--muted);font-size:10px}.card-top>:last-child{margin-left:auto}.node{border:1px solid #364458;display:grid;place-items:center;width:27px;height:27px;border-radius:50%;font-family:Consolas,monospace}.complete .node{background:#254338;color:var(--accent);border-color:#3d6b57}.level-card.locked .eyebrow{color:#7d8a9e}.level-card h3{margin:17px 0 8px;font-size:17px}.level-card p{font-size:12px;color:var(--muted);min-height:40px}.card-bottom{display:flex;align-items:center;justify-content:space-between;border-top:1px solid var(--line);padding-top:13px;font-size:10px}.card-bottom code{background:#1d2d38;padding:3px 8px;border-radius:4px}.ad-slot{display:flex;align-items:center;justify-content:center;flex-direction:column;gap:12px;border:1px dashed #2b3647;background:#101722;min-height:210px;margin:24px 0;border-radius:10px;color:#64738b}.ad-slot span{font-size:8px;letter-spacing:2px}.ad-slot strong{font-size:17px;font-weight:400}.ad-slot small{font:9px Consolas,monospace}.stats-grid{display:grid;grid-template-columns:repeat(4,1fr);border:1px solid var(--line);background:var(--panel);border-radius:12px;margin-bottom:30px}.stats-grid>div{padding:23px 26px;border-right:1px solid var(--line)}.stats-grid>div:last-child{border:0}.stats-grid small{font-size:9px;letter-spacing:1.3px;color:var(--muted)}.stats-grid strong{display:block;font-size:30px;margin-top:8px;font-weight:550;line-height:1.3}.stats-grid em{font-size:13px;font-style:normal;color:var(--muted);font-weight:400}.continue-panel{border:1px solid #35564d;background:linear-gradient(120deg,#1b3431,#162332);padding:35px;border-radius:12px}.continue-panel h2{font-size:30px;margin:16px 0 9px}.continue-panel p{font-size:13px}.continue-panel .button{margin-top:10px}.section-block{margin-top:28px}.section-heading{display:flex;align-items:center;justify-content:space-between;gap:16px;margin-bottom:18px}.section-heading h2{margin:0}.section-heading a{font-size:12px}.toolbox-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}.tool{border:1px solid var(--line);padding:17px;background:var(--panel);border-radius:9px}.tool code{display:block;font-size:20px;margin-bottom:7px}.tool span{display:block;font-size:11px}.tool small{font-size:9px;color:var(--accent)}.tool.locked code{color:#8c9aae}.tool.locked small{color:var(--muted)}.activity{border:1px solid var(--line);border-radius:10px;overflow:hidden;background:var(--panel)}.activity>div{display:flex;gap:16px;align-items:center;padding:16px 22px;border-bottom:1px solid var(--line)}.activity>div:last-child{border:0}.activity>div>span:first-child{flex:1}.activity strong{display:block;font-size:12px;font-weight:500}.activity small{color:var(--muted);font-size:10px}.activity code{font-size:10px}.activity>p{padding:20px;margin:0}.big-symbol{font-size:27px;display:block;margin:20px 0 14px}.operator-card .big-symbol{margin:0}.reference-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.operator-card h3{margin-top:20px}.operator-card p{font-size:12px}.operator-card small{font-size:9px;color:var(--muted)}pre{white-space:pre-wrap;overflow-wrap:anywhere;background:#0d1521;border:1px solid var(--line);padding:15px;border-radius:6px;font-size:12px}.filter-chips{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:25px}.breadcrumb{display:flex;gap:14px;align-items:center;flex-wrap:wrap;color:var(--muted);font-size:11px;margin-bottom:25px}.challenge-heading{margin-bottom:26px}.challenge-heading h1{font-size:36px}.xp-badge{color:var(--accent);border:1px solid #39554c;background:#172d28;padding:10px 19px;border-radius:8px;font-size:20px;font-weight:550;white-space:nowrap}.xp-badge small{font-size:11px}.challenge-layout{display:grid;grid-template-columns:minmax(0,1fr) 255px;gap:26px}.challenge-panel{padding:0;overflow:hidden}.requirement{padding:28px 30px 20px}.requirement h2{font-size:19px;line-height:1.65;margin:14px 0 10px;font-weight:500}.requirement p{font-size:11px}.wave-panel{border-top:1px solid var(--line);border-bottom:1px solid var(--line);background:#0c1521}.wave-panel .panel-top{border:0;padding:17px 24px 2px;font-size:9px}.waveform{width:100%;overflow-x:auto;padding:8px 10px}.waveform svg{display:block;width:100%;min-width:380px;height:auto}.wave-caption{font-size:9px;text-align:right;color:#687c95;padding:0 25px 15px}.editor-section{padding:25px 28px}.editor-section .section-heading>span{font-size:9px}.operator-chips{display:flex;gap:7px;align-items:center;flex-wrap:wrap;margin-bottom:15px}.operator-insert{font:12px Consolas,monospace;color:var(--accent);border:1px solid #354959;background:#182733;padding:4px 11px;border-radius:5px}.operator-chips>a{margin-left:auto;font-size:10px;color:var(--muted)}.code-editor{padding:20px 15px;background:#0a121e;border:1px solid #2b394e;border-radius:8px;font:13px/1.8 Consolas,monospace}.code-editor>div{display:flex}.code-editor code{color:#aab7ca}.line-no{color:#425571;font-size:11px;flex:0 0 28px;user-select:none}.syntax-purple{color:var(--purple)}.editor-input{padding:9px 0}.code-editor textarea{width:100%;border:0;background:transparent;resize:vertical;color:#e1effa;font-size:16px;padding:0 10px;min-height:65px;outline-offset:1px}.editor-toolbar{display:flex;align-items:center;gap:20px;margin-top:20px}.editor-toolbar .shortcut{margin-left:auto;font:9px Consolas,monospace}.check-item{display:flex;gap:14px;align-items:center}.check-item span{color:var(--accent);font-size:18px}.check-item p{margin:6px 0}.result{margin-top:22px;border-color:#6a543b}.result.perfect{border-color:#3f735e;background:#152b27}.result h2{font-size:19px;color:var(--accent);letter-spacing:.5px}.result p{font-size:13px}.result .metrics{display:flex;gap:30px;flex-wrap:wrap;margin:20px 0}.result .metrics strong{display:block;font-size:22px}.result .metrics small{color:var(--muted);font-size:10px}.result a{display:inline-block;margin-top:10px}.results-ad{max-width:400px;margin:40px auto 0}.hidden{display:none!important}#counterexample{margin-top:20px}#hints p{font-size:12px;border-top:1px solid var(--line);padding-top:15px;margin-top:20px}input,select,textarea{background:#0d1623;color:var(--text);border:1px solid #344257;border-radius:6px;padding:10px 12px;width:100%;max-width:100%}input[type=checkbox]{width:auto;accent-color:var(--accent)}select[multiple]{min-height:120px}label{display:block;font-size:12px;color:#b8c6d7;margin-bottom:7px}.helptext{display:block;color:var(--muted);font-size:11px;margin:6px 0}.helptext ul{padding-left:20px}.errorlist{color:var(--red);font-size:12px;list-style:none;padding:0}.auth-card{max-width:470px;margin:35px auto}.auth-card h1{font-size:30px;margin-top:18px}.auth-card>p:last-child{font-size:12px;text-align:center;margin:22px 0 0}.notice{padding:14px 20px;border:1px solid #385b4f;border-radius:8px;color:var(--accent);background:#182b27;margin-bottom:20px}.notice.error{border-color:#724448;background:#2d2027;color:var(--red)}.notice.warning{border-color:#786444;color:#e7cb8b;background:#2e281e}.filters{display:flex;gap:12px;margin-bottom:24px}.filters input{flex:2}.filters select{flex:1}.table-wrap{overflow:auto;padding:8px 22px}table{width:100%;border-collapse:collapse;text-align:left;white-space:nowrap}th{font-size:10px;text-transform:uppercase;letter-spacing:1px;color:var(--muted);font-weight:500;padding:15px 12px}td{font-size:12px;padding:20px 12px;border-top:1px solid var(--line)}.author-form{max-width:950px}.author-form p{margin-bottom:19px}.author-form .panel h2{font-size:21px;margin-bottom:25px}.formset-card{background:#0d1623;border:1px solid #304056;border-radius:9px;padding:24px;margin:20px 0}.formset-card label[for$="-DELETE"]{display:inline}.save-bar{position:sticky;bottom:15px;border:1px solid #425b5a;border-radius:10px;background:#1a3032;padding:14px 22px;display:flex;justify-content:space-between;align-items:center;margin:24px 0;z-index:2;box-shadow:0 10px 30px #0005}.save-bar span{font-size:12px;color:var(--muted)}.studio-actions{display:flex;flex-wrap:wrap;gap:16px;margin:25px 0}.studio-actions form{display:flex;gap:12px;flex-wrap:wrap}.wave-editor{overflow:auto;border:1px solid #304056;border-radius:9px;margin:15px 0 28px;background:#101a29;padding:16px}.wave-editor-toolbar{display:flex;gap:15px;align-items:center;flex-wrap:wrap;margin-bottom:15px}.wave-editor-toolbar label{margin:0}.wave-editor-toolbar input{width:75px;margin-left:8px}.wave-editor-grid{border-collapse:separate;border-spacing:3px}.wave-editor-grid td,.wave-editor-grid th{padding:2px;border:0}.wave-editor-grid td input{width:100px;min-width:100px;padding:7px}.wave-editor-grid th{font:11px Consolas,monospace;text-align:center}.wave-cell{width:30px;height:30px;border:1px solid #374760;border-radius:4px;background:#182637;color:#7f92ac;font:11px Consolas,monospace}.wave-cell.high{background:#366553;color:#c4ffe5;border-color:#568d76}.wave-delete{background:transparent;border:0;color:#c69398;padding:8px}.wave-editor .waveform{padding:12px 0 0}progress{height:10px;border:0;width:100%;accent-color:var(--accent);border-radius:10px;margin:12px 0 22px}progress::-webkit-progress-bar{background:#263445;border-radius:10px}progress::-webkit-progress-value{background:var(--accent);border-radius:10px}.skip,.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0)}.skip:focus{position:fixed;top:10px;left:10px;clip:auto;width:auto;height:auto;z-index:99;background:#12382c;padding:10px}.wave-tooltip{min-height:20px;font:10px Consolas,monospace;color:var(--muted);padding:0 15px}
@media(min-width:1450px){.hero{gap:90px}.hero-lab{margin-left:10px}}@media(max-width:1100px){.shell{padding:32px 28px 55px}.site-header{gap:25px}.site-header nav{gap:17px}.hero{gap:30px}.hero h1{font-size:46px}.hero-notes{gap:10px}.layout-sidebar,.challenge-layout{grid-template-columns:minmax(0,1fr) 225px}.toolbox-grid{grid-template-columns:repeat(2,1fr)}.account-nav{gap:12px}.account-nav form{display:none}}@media(max-width:820px){.site-header{flex-wrap:wrap;gap:15px;justify-content:space-between;padding:15px 24px}.site-header nav{order:3;width:100%;flex:auto;justify-content:center;border-top:1px solid var(--line);padding-top:12px}.hero{grid-template-columns:1fr;padding:30px 0 45px;gap:40px}.hero-copy>p{max-width:600px}.hero h1{font-size:52px}.hero-lab{max-width:620px;width:100%}.layout-sidebar,.challenge-layout{grid-template-columns:1fr}.layout-sidebar>aside,.challenge-layout>aside{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}.intro-strip{align-items:flex-start;flex-direction:column;gap:12px}.feature-grid{gap:24px}.stats-grid>div{padding:17px}.stats-grid strong{font-size:25px}.toolbox-grid{grid-template-columns:repeat(3,1fr)}.page-heading h1{font-size:32px}.filters{flex-wrap:wrap}.filters input,.filters select{flex:auto;width:45%}}@media(max-width:560px){.shell{padding:25px 17px 40px}.brand{font-size:19px}.brand-tag{display:none}.account-nav>a:not(.button):not(.avatar){display:none}.site-header nav{gap:20px}.site-header nav a{font-size:11px}.hero h1{font-size:43px}.hero-copy>p{font-size:14px}.hero .actions{flex-direction:column;align-items:stretch}.hero-notes{font-size:9px;gap:9px}.lab-body{padding:22px 17px}.lab-body h3{font-size:20px}.feature-grid,.level-grid,.reference-grid{grid-template-columns:1fr}.feature-grid{gap:14px;padding:30px 0}.feature-grid article{border-bottom:1px solid var(--line);padding:15px 0}.course-promo,.course-header,.page-heading{align-items:flex-start;flex-direction:column}.course-count{text-align:left;align-self:flex-start}.course-promo{gap:20px;padding:25px}.site-footer{flex-direction:column;gap:10px}.stats-grid{grid-template-columns:repeat(2,1fr)}.stats-grid>div:nth-child(2){border-right:0}.stats-grid>div:nth-child(-n+2){border-bottom:1px solid var(--line)}.layout-sidebar>aside,.challenge-layout>aside{grid-template-columns:1fr}.toolbox-grid{grid-template-columns:repeat(2,1fr)}.panel{padding:22px}.challenge-panel{padding:0}.requirement{padding:23px}.editor-section{padding:22px 17px}.editor-section .section-heading{flex-direction:column;align-items:flex-start;gap:5px}.editor-toolbar .shortcut{display:none}.editor-toolbar .button{margin-left:auto}.challenge-heading{flex-direction:row;align-items:center}.challenge-heading h1{font-size:28px}.xp-badge{font-size:15px;padding:8px 10px}.activity>div{flex-wrap:wrap;padding:15px}.activity .pill{font-size:8px}.activity>div>span:first-child{flex-basis:100%}.continue-panel{padding:26px}.page-heading h1{font-size:30px}.section-heading h2{font-size:21px}.waveform svg{min-width:380px}.auth-card{padding:23px}.hero-lab .waveform svg{min-width:340px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}

/* Operator detail pages and contextual help. */
.guide-links{list-style:none;padding:0;margin:18px 0}.guide-links li+li{border-top:1px solid var(--line)}.guide-links a{display:block;padding:11px 0;line-height:1.6}.guide-links code{display:inline-block;margin-right:7px}.operator-guide{max-width:850px}.operator-guide>h2{margin-top:28px}.operator-guide>h2:first-of-type{margin-top:0}.operator-guide>p{font-size:15px;line-height:1.9;margin-bottom:23px}.operator-guide .notice{margin-top:28px}.guide-link{display:inline-block;margin-top:8px;font-size:12px}.result .actions>a{display:inline-flex}