:root{--lightningcss-light:initial;--lightningcss-dark: ;color-scheme:light dark;--bg:#f5f5f4;--surface:#fff;--fg:#1c1917;--muted:#57534e;--line:#d6d3d1;--ok:#15803d;--bad:#b91c1c;--accent:#1d4ed8;--on-accent:#fff;--radius:10px;--space:1rem;--fs-sm:.85rem;--fs-base:1rem;--fs-lg:1.35rem;font-family:system-ui,sans-serif;font-size:var(--fs-base);line-height:1.5}@media (prefers-color-scheme:dark){:root{--lightningcss-light: ;--lightningcss-dark:initial;--bg:#1c1917;--surface:#292524;--fg:#f5f5f4;--muted:#a8a29e;--line:#44403c;--ok:#4ade80;--bad:#f87171;--accent:#93c5fd;--on-accent:#0c0a09}}*{box-sizing:border-box}body{background:var(--bg);color:var(--fg);margin:0}#app{max-width:1320px;margin:0 auto;padding:1.5rem clamp(1rem,3vw,2rem) 3rem}h1{margin:0;font-size:1.25rem}h2{font-size:var(--fs-lg);margin:.25rem 0 .75rem;line-height:1.3}h3{margin:0 0 .5rem;font-size:1rem}code,pre,textarea{font-family:ui-monospace,Consolas,monospace;font-size:.9rem}pre{white-space:pre-wrap;word-break:break-word}:focus-visible{outline:2px solid var(--accent);outline-offset:2px}header.top{border-bottom:1px solid var(--line);flex-wrap:wrap;justify-content:space-between;align-items:center;gap:1rem;margin-bottom:1.5rem;padding-bottom:1rem;display:flex}.brand{align-items:center;gap:.75rem;display:flex}.logo{background:var(--accent);width:2.25rem;height:2.25rem;color:var(--on-accent);border-radius:8px;place-items:center;font-size:1.2rem;font-weight:700;display:grid}.tagline{color:var(--muted);font-size:var(--fs-sm);margin:0}.status{flex-wrap:wrap;align-items:center;gap:.5rem .75rem;display:flex}.field{font-size:var(--fs-sm);color:var(--muted);align-items:center;gap:.4rem;display:inline-flex}.counts{gap:.4rem;display:inline-flex}.count{border:1px solid var(--line);font-size:var(--fs-sm);color:var(--muted);background:var(--surface);border-radius:999px;padding:.15rem .6rem}select{font:inherit;color:var(--fg);border:1px solid var(--line);background:var(--surface);border-radius:6px;padding:.35rem .5rem}dialog.topics{border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);width:calc(100% - 2rem);max-width:34rem;color:var(--fg);padding:1.25rem 1.5rem}dialog.topics::backdrop{background:#00000073}dialog.topics h2{margin-top:0}dialog.topics fieldset{border:1px solid var(--line);border-radius:10px;grid-template-columns:repeat(auto-fill,minmax(12rem,1fr));gap:.55rem 1rem;margin:0 0 1rem;padding:.75rem 1rem 1rem;display:grid}dialog.topics input[type=checkbox]{accent-color:var(--accent);flex:none;width:1rem;height:1rem;margin:0}dialog.topics .topic-option{align-items:center}dialog.topics .row{margin:.25rem 0 1rem}dialog.topics .row:last-of-type{margin-bottom:0}dialog.topics legend{color:var(--fg);padding:0 .35rem;font-weight:600}dialog.confirm{max-width:26rem}dialog.confirm .row{justify-content:flex-end;margin-bottom:0}.topic-option{align-items:baseline;gap:.4rem;display:flex}.topics-msg{color:var(--bad);min-height:1.25em;margin:0}.question{gap:1.5rem;display:grid}.pane{min-width:0}.pane.problem{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:1rem 1.25rem}@media (width>=1100px){.question{grid-template-columns:minmax(0,5fr) minmax(0,7fr);align-items:start}.pane.problem{max-height:calc(100vh - 2rem);position:sticky;top:1rem;overflow:auto}}.meta{color:var(--muted);font-size:var(--fs-sm);flex-wrap:wrap;align-items:center;gap:.5rem;margin:0;display:flex}.badge{border:1px solid;border-radius:999px;padding:.1rem .5rem;font-size:.8rem;font-weight:600}.unlock{color:var(--muted);font-size:.8rem}.diff-beginner{color:#0f766e}.diff-easy{color:var(--ok)}.diff-medium{color:#b45309}.diff-hard{color:#7c3aed}@media (prefers-color-scheme:dark){.diff-beginner{color:#5eead4}.diff-medium{color:#fbbf24}.diff-hard{color:#c4b5fd}}.statement{margin:0 0 1rem}.example strong{font-size:var(--fs-sm)}.example pre{background:color-mix(in srgb, var(--line) 30%, transparent);border:1px solid var(--line);border-radius:8px;margin:.25rem 0 .75rem;padding:.5rem .75rem}.constraints{color:var(--muted);font-size:var(--fs-sm);margin-bottom:0}.filters{flex-wrap:wrap;align-items:center;gap:.75rem 1.25rem;margin:0 0 1rem;display:flex}.problems section h3{margin:1.25rem 0 .25rem}.editor{border:1px solid var(--line);border-radius:var(--radius);resize:vertical;background:var(--surface);height:300px;min-height:160px;overflow:hidden}.editor:focus-within{outline:2px solid var(--accent);outline-offset:2px}.editor .cm-editor{height:100%;font-size:.95rem}.editor .cm-editor.cm-focused{outline:none}.editor .cm-scroller{font-family:ui-monospace,Consolas,monospace;line-height:1.5}.row{color:var(--muted);flex-wrap:wrap;align-items:center;gap:.75rem;margin:.75rem 0 1rem;display:flex}.row small{font-size:.8rem}button{font:inherit;border:1px solid var(--line);background:var(--surface);color:var(--fg);cursor:pointer;border-radius:6px;padding:.4rem .9rem}button:hover:not(:disabled){background:color-mix(in srgb, var(--accent) 10%, var(--surface))}button:disabled{opacity:.5;cursor:not-allowed}.run,.continue{background:var(--accent);color:var(--on-accent);border-color:var(--accent);font-weight:600}.run{padding:.55rem 1.4rem}.run:hover:not(:disabled),.continue:hover:not(:disabled){background:color-mix(in srgb, var(--accent) 85%, var(--fg))}.danger{background:var(--bad);color:var(--on-accent);border-color:var(--bad);font-weight:600}.danger:hover:not(:disabled){background:color-mix(in srgb, var(--bad) 85%, var(--fg))}.link{color:var(--accent);background:0 0;border:0;padding:0;text-decoration:underline}.link:hover:not(:disabled){background:0 0}.tests{border-collapse:separate;border-spacing:0;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);width:100%;margin:.5rem 0 1rem;overflow:hidden}.tests caption{text-align:left;padding-bottom:.35rem;font-weight:600}.tests th{text-transform:uppercase;letter-spacing:.04em;color:var(--muted);font-size:.75rem}.tests th,.tests td{text-align:left;border-bottom:1px solid var(--line);vertical-align:top;overflow-wrap:anywhere;padding:.5rem .75rem}.tests tbody tr:last-child td{border-bottom:0}.tests td small{color:var(--muted)}tr.ok td:first-child{color:var(--ok);white-space:nowrap;font-weight:600}tr.bad td:first-child{color:var(--bad);white-space:nowrap;font-weight:600}tr.first-fail{background:color-mix(in srgb, var(--bad) 10%, transparent)}.empty{color:var(--muted)}.reason{background:var(--surface);border:1px solid var(--line);border-left:4px solid var(--bad);border-radius:var(--radius);margin-bottom:1rem;padding:.5rem 1rem}.reason p{margin:.35rem 0}.hint{color:var(--muted)}.pass{color:var(--ok);font-weight:600}.output{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);margin-bottom:1rem;padding:.5rem 1rem}.output h3{margin:.25rem 0;font-size:.95rem}.output-heading{margin:.25rem 0;font-weight:600}.console{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);margin-bottom:1rem;padding:.5rem 1rem}.console summary{cursor:pointer;font-weight:600}.console .empty{margin:.35rem 0}.console-tabs{flex-wrap:wrap;gap:.35rem;margin:.6rem 0 .5rem;display:flex}.console-tab{border:1px solid var(--line);color:var(--muted);cursor:pointer;background:0 0;border-radius:999px;padding:.25rem .7rem;font:600 .8rem ui-monospace,Consolas,monospace}.console-tab:hover{color:var(--fg)}.console-tab[aria-selected=true]{color:#e5e5e5;background:#1e1e1e;border-color:#1e1e1e}.console-tab.ok .console-result{color:var(--ok)}.console-tab.bad .console-result{color:var(--bad)}.console-tab[aria-selected=true].ok .console-result{color:#4ade80}.console-tab[aria-selected=true].bad .console-result{color:#f87171}.console-count.muted{opacity:.7;font-weight:400}.console-lines{color:#e5e5e5;background:#1e1e1e;border-radius:8px;max-height:240px;padding:.6rem .8rem;font-family:ui-monospace,Consolas,monospace;font-size:.85rem;line-height:1.55;overflow:auto}.console-caption{color:#8b8b8b;margin-bottom:.3rem;padding-bottom:.4rem;font:.78rem ui-monospace,Consolas,monospace}.console-caption:before{content:"> "}.console-line{white-space:pre-wrap;overflow-wrap:anywhere;border-radius:3px;padding:0 .25rem}.console-none{color:#8b8b8b;font-style:italic}.console-lines .lvl-warn{color:#fbbf24;background:#fbbf241a}.console-lines .lvl-error{color:#f87171;background:#f871711f}.console-lines .lvl-debug,.console-lines .console-cut{color:#8b8b8b}.lvl-warn{color:#b45309;background:#b453091a}.lvl-error{color:var(--bad);background:color-mix(in srgb, var(--bad) 10%, transparent)}.lvl-debug,.console-cut{color:var(--muted)}@media (prefers-color-scheme:dark){.lvl-warn{color:#fbbf24;background:#fbbf241a}}.answer pre{border:1px dashed var(--line);border-radius:8px;padding:.75rem}.solution{background:var(--surface);border:1px solid var(--line);border-left:4px solid var(--ok);border-radius:var(--radius);margin-bottom:1rem;padding:.75rem 1.25rem}.solution pre{background:color-mix(in srgb, var(--line) 30%, transparent);border-radius:8px;padding:.75rem;overflow-x:auto}.solution li{margin-bottom:.25rem}.concepts h4{margin:1rem 0 .5rem;font-size:.95rem}.concepts details{border-top:1px solid var(--line);padding:.5rem 0}.concepts summary{cursor:pointer;font-weight:600}.concepts p{margin:.5rem 0}.concepts ol{margin:.25rem 0 .5rem;padding-left:1.4rem}.build h4{margin:1rem 0 .5rem;font-size:.95rem}.build ol{margin:.25rem 0 .5rem;padding-left:1.4rem}.build li{margin-bottom:.75rem}.build li p{margin:0 0 .35rem}.build pre{background:color-mix(in srgb, var(--line) 30%, transparent);border-radius:8px;margin:0;padding:.6rem .75rem;overflow-x:auto}footer{border-top:1px solid var(--line);text-align:center;margin-top:2.5rem;padding-top:1rem}.reset{color:var(--muted);font-size:var(--fs-sm);background:0 0;border:0;text-decoration:underline}.reset:hover:not(:disabled){color:var(--bad);background:0 0}.sr-only{clip:rect(0 0 0 0);width:1px;height:1px;position:absolute;overflow:hidden}.auth-brand{text-align:center;flex-direction:column;justify-content:center;max-width:24rem;margin:3rem auto 0}.auth-brand .logo{margin:0 auto .75rem}.auth{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);max-width:24rem;margin:1.25rem auto 0;padding:1.5rem 1.5rem 1.25rem}.auth h2{margin:0 0 1rem}.auth-form{gap:.9rem;display:grid}.auth-field{font-size:var(--fs-sm);color:var(--muted);gap:.3rem;display:grid}.auth-field input{font:inherit;color:var(--fg);background:var(--bg);border:1px solid var(--line);border-radius:6px;width:100%;padding:.55rem .7rem}.auth-field input:focus-visible{outline:2px solid var(--accent);outline-offset:1px}.auth-submit{background:var(--accent);width:100%;color:var(--on-accent);border:0;padding:.6rem .9rem;font-weight:600}.auth-submit:hover:not(:disabled){background:var(--accent);filter:brightness(1.08)}.auth-submit:disabled{opacity:.7;cursor:wait;filter:none}.auth-error{color:var(--bad);font-size:var(--fs-sm);margin:.75rem 0 0}.auth-message{color:var(--ok);font-size:var(--fs-sm);margin:.75rem 0 0}.auth-links{font-size:var(--fs-sm);flex-wrap:wrap;justify-content:center;gap:.4rem 1rem;margin:1rem 0 0;display:flex}.auth .link{font-size:var(--fs-sm)}.privacy-note{text-align:center;max-width:26rem;font-size:var(--fs-sm);color:var(--muted);margin:1rem auto 0}.auth+.privacy-note{margin-top:1rem}header.top{align-items:center}.tabs{border:1px solid var(--line);background:var(--surface);border-radius:999px;gap:.25rem;padding:.2rem;display:flex}.tab{color:var(--muted);font:inherit;cursor:pointer;background:0 0;border:0;border-radius:999px;padding:.4rem .9rem}.tab:hover:not(.active){color:var(--fg)}.tab.active{background:var(--accent);color:var(--on-accent)}.account{position:relative}.account-btn{text-overflow:ellipsis;white-space:nowrap;max-width:14rem;overflow:hidden}.menu{z-index:20;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);gap:.15rem;min-width:15rem;padding:.5rem;display:grid;position:absolute;top:calc(100% + .5rem);right:0;box-shadow:0 8px 24px #00000026}.menu-row{padding:.25rem .5rem .5rem}.menu-row .field{justify-content:space-between;width:100%}.menu-item{text-align:left;color:var(--fg);font:inherit;cursor:pointer;background:0 0;border:0;border-radius:6px;padding:.5rem .6rem}.menu-item:hover{background:var(--bg)}.danger-text{color:var(--bad)}.next{border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);flex-wrap:wrap;justify-content:space-between;align-items:center;gap:.75rem 1rem;margin:0 0 1rem;padding:.75rem 1rem;display:flex}.next p{margin:0}.next .continue{margin-left:auto}.hint-btn{font-size:var(--fs-sm);margin:0 0 1rem}.hint-box{border:1px solid var(--line);border-left:3px solid var(--accent);border-radius:var(--radius);background:var(--surface);font-size:var(--fs-sm);margin:0 0 1rem;padding:.75rem 1rem}.hint-box ul{margin:.5rem 0 0;padding-left:1.1rem}.hint-box li{margin:.25rem 0}.sitting-note{font-size:var(--fs-sm);color:var(--muted);margin:-.25rem 0 1rem}.reveal-ask{border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);margin:0 0 1rem;padding:.75rem 1rem}.reveal-ask p{margin:0 0 .6rem}.how{border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);margin:0 0 1rem;padding:.6rem 1rem}.how summary{cursor:pointer;font-weight:600}.how ul{margin:.6rem 0 0;padding-left:1.2rem}