:root{--bg:#fff;--fg:#0a0a0a;--muted:#64645f;--line:#e3e3df;--soft:#f4f4f1;--display:"IBM Plex Sans Condensed", "Arial Narrow", system-ui, sans-serif;--sans:"IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif;--mono:"IBM Plex Mono", ui-monospace, Menlo, Consolas, monospace;--lightningcss-light:initial;--lightningcss-dark: ;color-scheme:light}:root[data-theme=dark]{--bg:#0b0b0a;--fg:#f3f3f0;--muted:#9b9b95;--line:#2a2a27;--soft:#161615;--lightningcss-light: ;--lightningcss-dark:initial;color-scheme:dark}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:80px}body{background:var(--bg);color:var(--fg);font-family:var(--sans);-webkit-font-smoothing:antialiased;margin:0;font-size:16px;line-height:1.65}body:before{content:"";height:env(safe-area-inset-top,0px);z-index:10;background:var(--bg);position:fixed;inset:0 0 auto}a{color:inherit}img{max-width:100%}[hidden]{display:none!important}button,input,textarea{font:inherit;color:inherit}:focus-visible{outline:2px solid var(--fg);outline-offset:2px}.bar{top:env(safe-area-inset-top,0px);z-index:9;background:var(--bg);border-bottom:1px solid var(--line);position:sticky}.bar-in,.wrap{max-width:1200px;padding-left:max(16px, env(safe-area-inset-left,0px));padding-right:max(16px, env(safe-area-inset-right,0px));margin:0 auto}.bar-in{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:16px;min-height:56px;padding-block:8px;display:flex}.brand{font-family:var(--display);align-items:center;gap:10px;font-size:18px;font-weight:700;text-decoration:none;display:flex}.brand i{background:var(--fg);border-radius:50%;width:14px;height:14px;display:inline-block}.bar nav{align-items:center;gap:4px;display:flex}.theme-btn{border:1px solid var(--line);background:var(--bg);cursor:pointer;border-radius:50%;width:32px;height:32px;margin-left:6px;font-size:15px;line-height:1}.theme-btn:hover{border-color:var(--fg)}.bar nav a{color:var(--muted);border-radius:999px;padding:6px 12px;font-size:14px;text-decoration:none}.bar nav a.on{background:var(--fg);color:var(--bg)}.bar nav a:hover:not(.on){color:var(--fg)}.wrap{padding-block:40px 96px}h1,h2,h3{font-family:var(--display);text-wrap:balance;margin:0;line-height:1.15}h1{letter-spacing:-.01em;font-size:clamp(34px,6vw,52px);font-weight:600}h2{font-size:26px;font-weight:600}h3{font-size:19px;font-weight:600}p{margin:0}.lead{color:var(--muted);max-width:62ch;font-size:18px}.muted{color:var(--muted)}.eyebrow{font-family:var(--mono);letter-spacing:.08em;text-transform:uppercase;color:var(--muted);font-size:12px}.stack{flex-direction:column;gap:16px;display:flex}.row{flex-wrap:wrap;align-items:center;gap:8px;display:flex}code{font-family:var(--mono);background:var(--soft);border-radius:4px;padding:1px 5px;font-size:.88em}.hint{color:var(--muted);font-size:13px}.btn{border:1px solid var(--fg);background:var(--fg);color:var(--bg);cursor:pointer;border-radius:999px;align-items:center;gap:8px;padding:9px 18px;font-size:14px;font-weight:500;text-decoration:none;display:inline-flex}.btn.ghost{color:var(--fg);background:0 0}.btn:disabled{opacity:.45;cursor:default}.btn.sm{padding:5px 12px;font-size:13px}.prog{background:var(--line);border-radius:3px;height:3px;overflow:hidden}.prog b{background:var(--fg);height:100%;transition:width .6s;display:block}.panel{border:1px solid var(--fg);border-radius:12px;flex-direction:column;gap:14px;padding:22px;display:flex}.panel.soft{border-color:var(--line);background:var(--soft)}.tag{font-family:var(--mono);letter-spacing:.06em;text-transform:uppercase;border:1px solid var(--line);color:var(--muted);border-radius:4px;padding:1px 6px;font-size:11px}.hero{flex-direction:column;gap:14px;margin-bottom:28px;display:flex}.stats{color:var(--muted);flex-wrap:wrap;gap:28px;margin-top:8px;font-size:14px;display:flex}.stats strong{font-family:var(--display);color:var(--fg);font-variant-numeric:tabular-nums;font-size:28px;font-weight:600;display:block}.unit{border-top:1px solid var(--line);grid-template-columns:72px 1fr;gap:8px 20px;padding:32px 0;display:grid}.unit-n{font-family:var(--display);font-variant-numeric:tabular-nums;font-size:56px;font-weight:700;line-height:.9}.unit-h{flex-direction:column;gap:6px;min-width:0;display:flex}.unit-h p{color:var(--muted)}.lessons{grid-column:2;margin:10px 0 0;padding:0;list-style:none}.lessons a{border-bottom:1px solid var(--line);grid-template-columns:22px 52px 1fr auto;align-items:baseline;gap:10px;padding:11px 0;text-decoration:none;display:grid}.lessons a:hover .lt{text-underline-offset:3px;text-decoration:underline}.dot{border:1.5px solid var(--fg);border-radius:50%;width:10px;height:10px;display:inline-block;transform:translateY(1px)}.dot.done{background:var(--fg)}.lid,.lmin{font-family:var(--mono);color:var(--muted);white-space:nowrap;font-size:12px}.vid{font-family:var(--mono);border:1px solid var(--line);color:var(--muted);border-radius:3px;margin-left:6px;padding:0 4px;font-size:10px}@media (max-width:560px){.unit{grid-template-columns:1fr}.unit-n{font-size:40px}.lessons{grid-column:1}.lessons a{grid-template-columns:18px 40px 1fr}.lmin{display:none}}.crumb{color:var(--muted);flex-wrap:wrap;gap:8px;font-size:13px;display:flex}.crumb a{text-decoration:none}.crumb a:hover{text-decoration:underline}.lesson-h{flex-direction:column;gap:12px;margin:14px 0 28px;display:flex}.lesson-grid{grid-template-columns:230px minmax(0,1fr);align-items:start;gap:56px;display:grid}.lesson-side{top:calc(env(safe-area-inset-top,0px) + 84px);max-height:calc(100vh - 110px);padding-bottom:16px;position:sticky;overflow-y:auto}.lesson-main{min-width:0;max-width:900px}@media (max-width:980px){.lesson-grid{grid-template-columns:minmax(0,1fr)}.lesson-side{display:none}}.toc{flex-direction:column;gap:8px;display:flex}.toc-meta{color:var(--muted);font-size:12px}.toc ol{border-left:1px solid var(--line);flex-direction:column;margin:8px 0 0;padding:0;font-size:14px;list-style:none;display:flex}.toc li a{color:var(--muted);border-left:2px solid #0000;margin-left:-1px;padding:6px 0 6px 14px;line-height:1.35;text-decoration:none;display:block}.toc li a:hover{color:var(--fg)}.toc li.on a{color:var(--fg);border-left-color:var(--fg);font-weight:500}.toc-play{vertical-align:middle;margin-left:6px;font-size:8px}.home{flex-direction:column;display:flex}.sec{flex-direction:column;gap:14px;margin-bottom:44px;display:flex}.sec>p,.sec li{max-width:66ch}.sec ul{flex-direction:column;gap:6px;margin:0;padding-left:20px;display:flex}.callout{border-left:3px solid var(--fg);flex-direction:column;gap:6px;padding:4px 0 4px 16px;display:flex}.callout.warn{border-left-style:double;border-left-width:5px}.callout.example{border-left-style:dashed}.callout p{max-width:66ch;font-size:15px}.take{flex-direction:column;gap:10px;margin:0;padding:0;list-style:none;display:flex}.take li{grid-template-columns:20px 1fr;gap:8px;display:grid}.take li:before{content:"→";font-family:var(--mono)}.gloss{grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:12px 24px;margin:0;display:grid}.gloss div{border-top:1px solid var(--line);padding-top:10px}.gloss dt{font-family:var(--mono);font-size:13px;font-weight:500}.gloss dd{color:var(--muted);margin:4px 0 0;font-size:14px}.video{margin:0 0 32px}.video-frame{aspect-ratio:16/9;background:var(--soft);border:1px solid var(--line);border-radius:10px;max-width:100%;position:relative;overflow:hidden}.video-frame iframe{border:0;width:100%;height:100%;position:absolute;inset:0}.video-poster{all:unset;cursor:pointer;place-items:center;display:grid;position:absolute;inset:0}.video-poster img{object-fit:cover;filter:grayscale()contrast(1.05);width:100%;height:100%;transition:filter .3s;position:absolute;inset:0}.video-poster:hover img,.video-poster:focus-visible img{filter:none}.video-poster .play-icon{background:var(--fg);width:68px;height:68px;color:var(--bg);border-radius:50%;place-items:center;padding-left:4px;font-size:22px;display:grid;position:relative}.video figcaption{flex-wrap:wrap;align-items:baseline;gap:4px 14px;margin-top:10px;font-size:14px;display:flex}.video figcaption a{color:var(--muted);margin-left:auto;font-size:13px}.dg{border:1px solid var(--line);background:var(--bg);border-radius:10px;margin:6px 0 0;padding:16px}.dg-scroll{overflow-x:auto}.dg svg{width:100%;height:auto;margin:0 auto;display:block}.dg figcaption{color:var(--muted);flex-wrap:wrap;justify-content:space-between;align-items:flex-start;gap:12px;margin-top:12px;font-size:13px;display:flex}.dg figcaption button{border:1px solid var(--line);cursor:pointer;color:var(--fg);white-space:nowrap;background:0 0;border-radius:999px;padding:3px 10px;font-size:12px}.dg figcaption button.primary{background:var(--fg);color:var(--bg);border-color:var(--fg)}.dg figcaption button:disabled{opacity:.35;cursor:default}.dg text{font-family:var(--sans);fill:var(--fg);font-size:13px}.dg text.sm{font-size:11.5px}.dg text.xs{font-size:10.5px}.dg text.b{font-weight:600}.dg text.dim{fill:var(--muted)}.dg text.sub{font-family:var(--mono);fill:var(--muted);font-size:10.5px}.dg text.inv{fill:var(--bg);font-weight:600}.dg text.sub.inv{opacity:.75;font-weight:400}.dg .box{fill:var(--bg);stroke:var(--fg);stroke-width:1.3px}.dg .box.plain{stroke:var(--line)}.dg .box.soft{fill:var(--soft);stroke:var(--line)}.dg .box.inv{fill:var(--fg);stroke:var(--fg)}.dg .bar{fill:var(--fg)}.dg .ln{stroke:var(--fg);stroke-width:1.3px;fill:none}.dg .dash{stroke:var(--muted);stroke-width:1px;stroke-dasharray:4 4;fill:none}.dg .mk,.dg .pkt{fill:var(--fg)}.dg .pop{transform-box:fill-box;transform-origin:50%;animation:.5s cubic-bezier(.2,.7,.2,1) both pop}.dg .draw{stroke-dasharray:1;animation:.55s ease-out both draw}.dg .grow{transform-box:fill-box;transform-origin:0;animation:.7s cubic-bezier(.2,.7,.2,1) both grow}@keyframes pop{0%{opacity:0;transform:translateY(8px)scale(.97)}}@keyframes draw{0%{stroke-dashoffset:1px}}@keyframes grow{0%{transform:scaleX(0)}}.stepper:focus{outline:none}.stepper:focus-visible{outline:2px solid var(--fg)}.step-top{flex-wrap:wrap;justify-content:space-between;align-items:center;gap:12px;margin-bottom:10px;display:flex}.step-dots{gap:6px;display:flex}.step-dots button{background:var(--line);cursor:pointer;border:0;border-radius:3px;width:22px;height:6px;padding:0}.step-dots button.past{background:var(--muted)}.step-dots button.on{background:var(--fg)}.step-note{background:var(--soft);border-radius:8px;min-height:52px;margin-top:12px;padding:12px 14px;font-size:15px;animation:.35s both fade}@keyframes fade{0%{opacity:0;transform:translateY(4px)}}@media (prefers-reduced-motion:reduce){.dg .pop,.dg .draw,.dg .grow,.step-note{animation:none}.dg .pkt{display:none}}.codewrap{flex-direction:column;gap:6px;display:flex}pre.code{background:var(--soft);border:1px solid var(--line);font-family:var(--mono);border-radius:10px;margin:0;padding:16px;font-size:13px;line-height:1.55;overflow-x:auto}pre.code code{font-size:inherit;background:0 0;padding:0}.code-h{font-family:var(--mono);letter-spacing:.06em;text-transform:uppercase;color:var(--muted);justify-content:space-between;align-items:center;font-size:11px;display:flex}.code-h button{cursor:pointer;color:var(--muted);font-family:var(--mono);letter-spacing:.06em;text-transform:uppercase;background:0 0;border:none;font-size:11px}.q{border-top:1px solid var(--line);flex-direction:column;gap:10px;padding-top:14px;display:flex}.q:first-child{border-top:0;padding-top:0}.opts{gap:8px;display:grid}.opt{text-align:left;background:var(--bg);border:1px solid var(--line);cursor:pointer;border-radius:8px;align-items:baseline;gap:10px;padding:10px 14px;display:flex}.opt:hover:not(:disabled){border-color:var(--fg)}.opt .k{font-family:var(--mono);color:var(--muted);font-size:12px}.opt.right{background:var(--fg);color:var(--bg);border-color:var(--fg)}.opt.right .k{color:var(--bg)}.opt.wrong-sel{color:var(--muted);border-style:dashed}.opt.wrong{color:var(--muted);text-decoration:line-through}.opt:disabled{cursor:default}.why{color:var(--muted);font-size:14px}.score-line{font-family:var(--mono);font-size:13px}.pager{border-top:1px solid var(--line);flex-wrap:wrap;justify-content:space-between;gap:12px;margin-top:28px;padding-top:24px;display:flex}.pager a{flex-direction:column;gap:2px;min-width:0;max-width:48%;text-decoration:none;display:flex}.pager a:last-child{text-align:right;margin-left:auto}.pager small{color:var(--muted);font-size:12px}.grid2{grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:20px;margin-top:28px;display:grid}.card-big{font-family:var(--mono);word-break:break-all;min-height:44px;font-size:clamp(22px,5vw,30px);font-weight:500}.score{font-family:var(--mono);color:var(--muted);font-variant-numeric:tabular-nums;font-size:13px}.field{flex-direction:column;gap:6px;display:flex}.field label{font-size:13px;font-weight:500}.field input,.field textarea{border:1px solid var(--line);background:var(--bg);border-radius:8px;width:100%;padding:10px 12px}.field textarea{resize:vertical;min-height:180px;font-size:14px}.field input:focus,.field textarea:focus{border-color:var(--fg);outline:none}.status{align-items:center;gap:10px;font-size:14px;display:flex}.spin{border:2px solid var(--line);border-top-color:var(--fg);border-radius:50%;flex:none;width:12px;height:12px;animation:.8s linear infinite sp}@keyframes sp{to{transform:rotate(360deg)}}.chips{flex-wrap:wrap;gap:6px;display:flex}.chip{border:1px solid var(--line);border-radius:999px;padding:3px 10px;font-size:13px;text-decoration:none}.chip.have{background:var(--fg);color:var(--bg);border-color:var(--fg)}a.chip:hover{border-color:var(--fg)}.saved{margin:0;padding:0;list-style:none}.saved li{border-bottom:1px solid var(--line);justify-content:space-between;align-items:center;gap:12px;padding:10px 0;display:flex}.saved a{min-width:0;text-decoration:none}.saved a:hover{text-decoration:underline}details.qa{border-top:1px solid var(--line)}details.qa:last-child{border-bottom:1px solid var(--line)}details.qa summary{cursor:pointer;grid-template-columns:44px 1fr 18px;align-items:baseline;gap:12px;padding:18px 0;list-style:none;display:grid}details.qa summary::-webkit-details-marker{display:none}.qn{font-family:var(--display);font-variant-numeric:tabular-nums;font-size:22px;font-weight:700}.pl{font-family:var(--mono);transition:transform .2s}details.qa[open] .pl{transform:rotate(45deg)}.qmeta{font-family:var(--mono);letter-spacing:.06em;text-transform:uppercase;color:var(--muted);gap:8px;margin-top:6px;font-size:11px;display:flex}.qbody{flex-direction:column;gap:14px;padding:0 0 24px 56px;display:flex}@media (max-width:560px){.qbody{padding-left:0}}.two{grid-template-columns:1fr 1fr;gap:20px;display:grid}@media (max-width:620px){.two{grid-template-columns:1fr}}.play{border:1.5px solid var(--fg);background:var(--bg);border-radius:12px;flex-direction:column;gap:12px;padding:18px 20px;display:flex}.play-prompt{max-width:70ch;font-weight:500}.play-f{margin-top:4px}.play-res{font-family:var(--mono);font-size:13px}.order{flex-direction:column;gap:6px;margin:0;padding:0;list-style:none;display:flex}.order li{border:1px solid var(--line);background:var(--bg);border-radius:8px;grid-template-columns:28px 1fr auto;align-items:center;gap:10px;padding:8px 10px;transition:border-color .2s;display:grid}.order li.ok{border-color:var(--fg);background:var(--soft)}.order li.no{border-style:dashed}.order .num{font-family:var(--mono);color:var(--muted);text-align:center;font-size:12px}.order .mv{gap:4px;display:flex}.order .mv button{border:1px solid var(--line);background:var(--bg);cursor:pointer;border-radius:6px;width:30px;height:28px}.order .mv button:hover:not(:disabled){border-color:var(--fg)}.order .mv button:disabled{opacity:.3;cursor:default}.match{grid-template-columns:1fr 1fr;gap:12px 24px;display:grid}.match .col{flex-direction:column;gap:6px;min-width:0;display:flex}.chipbtn{text-align:left;border:1px solid var(--line);background:var(--bg);cursor:pointer;border-radius:8px;align-items:baseline;gap:8px;padding:8px 10px;font-size:14px;display:flex}.chipbtn:hover:not(:disabled){border-color:var(--fg)}.chipbtn:disabled{cursor:default;opacity:.55}.chipbtn.sel{border-color:var(--fg);box-shadow:inset 0 0 0 1px var(--fg)}.chipbtn.paired{background:var(--soft)}.chipbtn.ok{background:var(--fg);color:var(--bg);border-color:var(--fg)}.chipbtn.no{color:var(--muted);border-style:dashed;text-decoration:line-through}.tagn{font-family:var(--mono);min-width:14px;color:inherit;opacity:.7;font-size:11px}.pool{border:1px dashed var(--line);border-radius:8px;flex-wrap:wrap;gap:6px;padding:10px;display:flex}.buckets{gap:10px;display:grid}.bucket{border:1px solid var(--line);background:var(--soft);border-radius:10px;flex-direction:column;gap:8px;min-height:96px;padding:10px;display:flex}.bucket.armed{border-color:var(--fg);cursor:pointer}.bucket-h{font-family:var(--mono);letter-spacing:.06em;text-transform:uppercase;font-size:12px}.bucket-b{flex-direction:column;gap:6px;display:flex}pre.fill{white-space:pre-wrap;font-family:var(--mono);background:var(--soft);border:1px solid var(--line);border-radius:10px;margin:0;padding:14px 16px;font-size:13.5px;line-height:2.1;overflow-x:auto}pre.fill select{font-family:var(--mono);border:1px solid var(--fg);background:var(--bg);color:var(--fg);border-radius:6px;max-width:100%;padding:2px 4px;font-size:13px}pre.fill select.ok{background:var(--fg);color:var(--bg)}pre.fill select.no{border-style:dashed}@media (max-width:620px){.match{grid-template-columns:1fr}.buckets{grid-template-columns:1fr!important}}