/* AIED Guru — a teacher's working notebook. Chalkboard-green ink, marigold for the one thing to act on. */
:root{
  --paper:#f4f6f1; --sheet:#ffffff; --ink:#16231d; --muted:#56655d; --line:#d7ded6;
  --board:#1d5a45; --board-soft:#e3eee8; --marigold:#b9780a; --marigold-soft:#fbefd6; --code-bg:#eef2ec;
  --f-display:"Bricolage Grotesque","Segoe UI",system-ui,sans-serif;
  --f-body:"Noto Sans","Segoe UI",system-ui,-apple-system,sans-serif;
  --f-mono:"JetBrains Mono",ui-monospace,Consolas,monospace;
  --step--1:.85rem; --step0:1rem; --step1:1.2rem; --step2:1.5rem; --step3:2rem; --step4:clamp(2.2rem,6vw,3.4rem);
  --radius:10px;
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --paper:#0f1814; --sheet:#16211c; --ink:#e4ece7; --muted:#9db0a6; --line:#2a3a32;
  --board:#6fc7a2; --board-soft:#1b3129; --marigold:#f0b545; --marigold-soft:#33280f; --code-bg:#1b2822;
  color-scheme:dark}}
:root[data-theme="dark"]{
  --paper:#0f1814; --sheet:#16211c; --ink:#e4ece7; --muted:#9db0a6; --line:#2a3a32;
  --board:#6fc7a2; --board-soft:#1b3129; --marigold:#f0b545; --marigold-soft:#33280f; --code-bg:#1b2822;
  color-scheme:dark}

*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:4.5rem}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--f-body);font-size:var(--step0);line-height:1.65}
body:not(.l-en) .en, body.l-en .ms{display:none !important}
img{max-width:100%}
.wrap{max-width:62rem;margin:0 auto;padding-inline:clamp(16px,4vw,32px);padding-block:0 4rem}
.col{max-width:44rem}
a{color:var(--board)}
a:focus-visible,button:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid var(--marigold);outline-offset:2px}
h1,h2,h3{font-family:var(--f-display);line-height:1.15;text-wrap:balance;margin:0}
h2{font-size:var(--step3);font-weight:800;letter-spacing:-.01em}
h3{font-size:var(--step1);font-weight:700}
p{margin:0}
.eyebrow{font-family:var(--f-mono);font-size:var(--step--1);letter-spacing:.08em;text-transform:uppercase;color:var(--board)}
.skip{position:absolute;left:-999px;top:0;background:var(--board);color:var(--paper);padding:.5rem 1rem;z-index:10}
.skip:focus{left:1rem}

/* site bar */
.bar{position:sticky;top:0;z-index:5;background:var(--paper);border-bottom:1px solid var(--line)}
.bar-in{max-width:62rem;margin:0 auto;padding-inline:clamp(16px,4vw,32px);padding-block:.6rem;display:flex;gap:1rem;align-items:center;justify-content:space-between;flex-wrap:wrap}
.brand{font-family:var(--f-display);font-weight:800;font-size:1.05rem;color:var(--ink);text-decoration:none}
.brand b{color:var(--board)}
.bar-right{display:flex;gap:1rem;align-items:center;flex-wrap:wrap}
nav.site{display:flex;gap:.9rem;font-size:var(--step--1)}
nav.site a{text-decoration:none;color:var(--muted)}
nav.site a:hover,nav.site a[aria-current="page"]{color:var(--board)}
.lang{display:inline-flex;border:1px solid var(--line);border-radius:999px;overflow:hidden;background:var(--sheet)}
.lang button{font:600 var(--step--1)/1 var(--f-body);border:0;background:transparent;color:var(--muted);padding:.5rem .8rem;cursor:pointer}
.lang button[aria-pressed="true"]{background:var(--board);color:var(--paper)}

/* home */
.intro{padding-block:3.2rem 2rem;display:grid;gap:1rem}
.intro h1{font-size:var(--step4);font-weight:800;letter-spacing:-.02em;max-width:20ch}
.intro h1 em{font-style:normal;color:var(--board)}
.lede{font-size:var(--step1);color:var(--muted);max-width:40rem}
.posts{display:grid;gap:1rem;padding-block:1rem 2rem}
.card{display:grid;gap:.6rem;background:var(--sheet);border:1px solid var(--line);border-radius:var(--radius);padding:1.4rem 1.5rem;text-decoration:none;color:inherit;transition:border-color .15s}
.card:hover{border-color:var(--board)}
.card h2{font-size:var(--step2)}
.card .sum{color:var(--muted)}
.card.feature{border-left:4px solid var(--board)}
.meta{font-family:var(--f-mono);font-size:var(--step--1);color:var(--muted);display:flex;gap:.4rem .9rem;flex-wrap:wrap}
.tags{display:flex;gap:.4rem;flex-wrap:wrap}
.tag-chip{font-size:.75rem;background:var(--board-soft);color:var(--board);border-radius:999px;padding:.15rem .6rem}
.more{font-weight:600;color:var(--board)}
.section-head{padding-top:2rem;border-top:1px solid var(--line)}

/* post */
.crumbs{font-size:var(--step--1);color:var(--muted);padding-top:1.6rem}
.crumbs a{color:var(--muted)}
header.hero{padding-block:1.6rem 2.4rem;display:grid;gap:1.2rem}
header.hero h1{font-size:var(--step4);font-weight:800;letter-spacing:-.02em;max-width:20ch}
header.hero h1 em{font-style:normal;color:var(--board)}
.toc{display:flex;gap:.5rem;flex-wrap:wrap;font-size:var(--step--1)}
.toc a{text-decoration:none;border:1px solid var(--line);background:var(--sheet);border-radius:999px;padding:.25rem .75rem;color:var(--muted)}
.toc a:hover{color:var(--board);border-color:var(--board)}
.facts{display:flex;flex-wrap:wrap;gap:.6rem;margin-top:.4rem}
.chip{font-size:var(--step--1);border:1px solid var(--line);background:var(--sheet);border-radius:999px;padding:.3rem .8rem;color:var(--muted)}
.chip strong{color:var(--ink);font-variant-numeric:tabular-nums}
section{padding-block:3rem;border-top:1px solid var(--line);display:grid;gap:1.4rem;scroll-margin-top:4.5rem}
.stack{display:grid;gap:.9rem}
.prose{display:grid;gap:1rem}
.prose h2{font-size:var(--step2);margin-top:1rem}
.prose ul,.prose ol{margin:0;padding-left:1.2rem;display:grid;gap:.4rem}
.prose blockquote{margin:0;border-left:3px solid var(--board);padding-left:1rem;color:var(--muted)}
.prose code{font-family:var(--f-mono);font-size:.9em;background:var(--code-bg);padding:.1em .35em;border-radius:4px}

.types{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,18rem),1fr));gap:1rem}
.type{background:var(--sheet);border:1px solid var(--line);border-radius:var(--radius);padding:1.1rem 1.2rem;display:grid;gap:.6rem;align-content:start;min-width:0}
.type .top{display:flex;justify-content:space-between;align-items:baseline;gap:.6rem}
.pct{font-family:var(--f-display);font-weight:800;font-size:var(--step2);color:var(--board);font-variant-numeric:tabular-nums}
.meter{height:6px;background:var(--board-soft);border-radius:3px;overflow:hidden}
.meter i{display:block;height:100%;background:var(--board)}
.type .eg{font-size:var(--step--1);color:var(--muted);border-top:1px dashed var(--line);padding-top:.6rem}
.type .eg b{color:var(--ink)}
.cap{font-size:var(--step--1);color:var(--muted)}

.ev{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,19rem),1fr));gap:1.6rem}
.bars{display:grid;gap:.55rem}
.bars .row{display:grid;grid-template-columns:minmax(0,9.5rem) 1fr 3.2rem;gap:.6rem;align-items:center;font-size:var(--step--1)}
.bars .track{height:10px;background:var(--board-soft);border-radius:5px;overflow:hidden}
.bars .track i{display:block;height:100%;background:var(--board)}
.bars .row.low .track i{background:var(--marigold)}
.bars .v{text-align:right;font-variant-numeric:tabular-nums;font-weight:600}
.so{background:var(--marigold-soft);border-radius:var(--radius);padding:1rem 1.2rem;display:grid;gap:.5rem}
ul.plain{margin:0;padding-left:1.1rem;display:grid;gap:.4rem}

.tl{list-style:none;margin:0;padding:0;display:grid}
.tl li{display:grid;grid-template-columns:6.5rem 1fr;gap:1rem;padding-block:.8rem;border-bottom:1px solid var(--line)}
.tl time{font-family:var(--f-mono);font-size:var(--step--1);color:var(--board);font-weight:500;padding-top:.15rem}
.tl .what{min-width:0}
.tl .what b{display:block}
.tl .what span.d{color:var(--muted);font-size:.95rem}

.check{background:var(--sheet);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.check-scroll{overflow-x:auto}
table.grid{border-collapse:collapse;width:100%;min-width:34rem;font-size:.95rem}
table.grid th,table.grid td{padding:.7rem .8rem;border-bottom:1px solid var(--line);text-align:left;vertical-align:middle}
table.grid thead th{font-family:var(--f-mono);font-size:var(--step--1);letter-spacing:.06em;text-transform:uppercase;color:var(--muted);font-weight:500}
table.grid td.c{text-align:center;width:6.5rem}
table.grid input{width:1.15rem;height:1.15rem;accent-color:var(--board)}
.check-foot{padding:1rem 1.2rem;display:flex;flex-wrap:wrap;gap:1rem;align-items:center;justify-content:space-between;background:var(--board-soft)}
.result{font-weight:600}
.btn{font:600 var(--step--1)/1 var(--f-body);border:1px solid var(--board);background:transparent;color:var(--board);padding:.55rem .9rem;border-radius:999px;cursor:pointer}
.btn:hover{background:var(--board);color:var(--paper)}
.btn.solid{background:var(--board);color:var(--paper)}

.prompts{display:grid;gap:1rem}
details.p{background:var(--sheet);border:1px solid var(--line);border-radius:var(--radius)}
details.p summary{cursor:pointer;padding:1rem 1.2rem;display:flex;gap:.8rem;align-items:baseline;list-style:none}
details.p summary::-webkit-details-marker{display:none}
details.p summary::before{content:"+";font-family:var(--f-mono);color:var(--board);font-weight:500;width:1ch}
details.p[open] summary::before{content:"−"}
details.p summary h3{font-size:var(--step0)}
details.p summary .tag{margin-left:auto;font-size:var(--step--1);color:var(--muted);white-space:nowrap}
.p-body{padding:0 1.2rem 1.2rem;display:grid;gap:.8rem}
pre.prompt{margin:0;background:var(--code-bg);border-radius:8px;padding:1rem;font-family:var(--f-mono);font-size:.85rem;line-height:1.6;white-space:pre-wrap;word-break:break-word;color:var(--ink)}
.p-actions{display:flex;gap:.6rem;align-items:center;flex-wrap:wrap}
.copied{font-size:var(--step--1);color:var(--board)}
.tip{font-size:var(--step--1);color:var(--muted)}
.tip b{color:var(--ink)}

ol.steps{margin:0;padding:0;list-style:none;counter-reset:s;display:grid;gap:.9rem}
ol.steps li{counter-increment:s;display:grid;grid-template-columns:2.2rem 1fr;gap:.8rem}
ol.steps li::before{content:counter(s);font-family:var(--f-display);font-weight:800;color:var(--paper);background:var(--board);border-radius:50%;width:2rem;height:2rem;display:grid;place-items:center}

.rules{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,16rem),1fr));gap:1rem}
.rule{border-left:3px solid var(--board);padding:.2rem 0 .2rem 1rem;display:grid;gap:.3rem;min-width:0}
.rule.warn{border-left-color:var(--marigold)}
.rule small{color:var(--muted);font-family:var(--f-mono);font-size:.75rem;letter-spacing:.04em}
.refs{font-size:.92rem;color:var(--muted)}
.refs li{word-break:break-word}

.post-end{border-top:1px solid var(--line);padding-block:2rem;display:grid;gap:1rem}
.author{display:flex;gap:1rem;align-items:center}
.avatar{width:3rem;height:3rem;border-radius:50%;background:var(--board);color:var(--paper);display:grid;place-items:center;font-family:var(--f-display);font-weight:800;flex:none}
.share{display:flex;gap:.6rem;flex-wrap:wrap;align-items:center}

footer.site{border-top:1px solid var(--line);font-size:var(--step--1);color:var(--muted)}
footer.site .in{max-width:62rem;margin:0 auto;padding:2rem clamp(16px,4vw,32px);display:flex;gap:1rem;justify-content:space-between;flex-wrap:wrap}
footer.site a{color:var(--muted)}

@media (max-width:640px){.tl li{grid-template-columns:1fr;gap:.2rem}.bar-right{gap:.6rem}}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}.card{transition:none}}

/* ===== home news slider ===== */
.slider{position:relative;margin-top:1.4rem}
.sl-track{display:flex;overflow-x:auto;scroll-snap-type:x mandatory;scrollbar-width:none;border-radius:14px;-webkit-overflow-scrolling:touch}
.sl-track::-webkit-scrollbar{display:none}
.sl{flex:0 0 100%;scroll-snap-align:start;min-height:clamp(21rem,48vw,28rem);display:flex;align-items:flex-end;position:relative;color:#fff;isolation:isolate;overflow:hidden}
.sl::before{content:"";position:absolute;inset:0;z-index:-2;background:var(--g)}
.sl::after{content:"";position:absolute;inset:0;z-index:-1;opacity:.5;
  background:repeating-linear-gradient(135deg,rgba(255,255,255,.05) 0 2px,transparent 2px 22px),linear-gradient(to top,rgba(0,0,0,.45),transparent 65%)}
.s0{--g:linear-gradient(135deg,#0f3d2e 0%,#1d5a45 55%,#2c7a5d 100%)}
.s1{--g:linear-gradient(135deg,#12324a 0%,#1c5a73 60%,#2a7d8a 100%)}
.s2{--g:linear-gradient(135deg,#3b2a12 0%,#7a5410 60%,#b9780a 100%)}
.s3{--g:linear-gradient(135deg,#2a1f3d 0%,#47356b 60%,#6a52a0 100%)}
.s4{--g:linear-gradient(135deg,#3d1a22 0%,#722c3a 60%,#a14357 100%)}
.sl-in{padding:clamp(1.2rem,4vw,2.6rem);padding-bottom:clamp(3.6rem,7vw,4.6rem);display:grid;gap:.8rem;max-width:46rem}
.sl-kicker{font-family:var(--f-mono);font-size:var(--step--1);letter-spacing:.08em;text-transform:uppercase;color:#f0b545}
.sl h2{font-size:clamp(1.7rem,4.6vw,2.8rem);font-weight:800;letter-spacing:-.015em;line-height:1.1}
.sl h2 a{color:#fff;text-decoration:none}
.sl h2 a:hover{text-decoration:underline;text-underline-offset:.2em}
.sl-sum{color:rgba(255,255,255,.88);font-size:var(--step1);max-width:38rem}
.sl-meta{display:flex;flex-wrap:wrap;gap:.4rem .9rem;align-items:center;font-family:var(--f-mono);font-size:var(--step--1);color:rgba(255,255,255,.8)}
.sl-meta .tag-chip{background:rgba(255,255,255,.16);color:#fff}
.sl-cta{justify-self:start;background:#fff;color:#16231d;font-weight:700;text-decoration:none;border-radius:999px;padding:.6rem 1.1rem;margin-top:.3rem}
.sl-cta:hover{background:#f0b545}
.sl a:focus-visible{outline:3px solid #f0b545;outline-offset:3px}
.sl-ctrl{position:absolute;left:clamp(1.2rem,4vw,2.6rem);bottom:1rem;display:flex;align-items:center;gap:.5rem}
.sl-btn{width:2.4rem;height:2.4rem;border-radius:50%;border:1px solid rgba(255,255,255,.5);background:rgba(0,0,0,.35);color:#fff;font:700 1.2rem/1 var(--f-body);cursor:pointer;display:grid;place-items:center;padding:0}
.sl-btn:hover{background:rgba(0,0,0,.6)}
.sl-btn:focus-visible,.sl-dot:focus-visible{outline:3px solid #f0b545;outline-offset:2px}
.sl-play{font-size:.7rem}
.sl-dots{display:flex;gap:.4rem;padding-inline:.3rem}
.sl-dot{width:.7rem;height:.7rem;padding:0;border-radius:999px;border:0;background:rgba(255,255,255,.5);cursor:pointer;transition:width .2s,background .2s}
.sl-dot[aria-selected="true"]{width:1.8rem;background:#f0b545}
.tagline{display:grid;gap:.4rem;padding-block:1.6rem 2rem}
.posts.grid{grid-template-columns:repeat(auto-fill,minmax(min(100%,19rem),1fr));padding-block:1rem 1.4rem}
@media (max-width:640px){.sl-sum{font-size:1rem}.sl-in{padding-bottom:4.4rem}}
@media (prefers-reduced-motion:reduce){.sl-track{scroll-behavior:auto}.sl-dot{transition:none}}

/* ===== covers ===== */
.sl::before{background:var(--img,none) center/cover no-repeat,var(--g)}
.sl::after{background:linear-gradient(90deg,rgba(0,0,0,.6) 0,rgba(0,0,0,.2) 60%,transparent 85%),linear-gradient(to top,rgba(0,0,0,.5),transparent 60%);opacity:1}
.card .thumb{display:block;width:calc(100% + 3rem);max-width:none;margin:-1.4rem -1.5rem .3rem;aspect-ratio:1200/630;object-fit:cover;border-radius:var(--radius) var(--radius) 0 0;background:var(--board-soft)}
.post-cover{display:block;width:100%;max-height:22rem;object-fit:cover;border-radius:12px;margin-top:1rem}

/* ===== slider: split layout (text | illustration), stacked on phones ===== */
.sl{display:grid;grid-template-columns:minmax(0,5fr) minmax(0,6fr);align-items:stretch;min-height:clamp(21rem,38vw,26rem);background:var(--g)}
.sl::before{content:"";position:static;grid-column:2;grid-row:1;z-index:auto;background:var(--img,none) 85% center/cover no-repeat;box-shadow:inset 36px 0 36px -24px rgba(0,0,0,.4)}
.sl::after{content:none}
.sl-in{grid-column:1;grid-row:1;align-self:center;max-width:none}
.sl h2{font-size:clamp(1.5rem,3.2vw,2.3rem)}
.post-cover{object-position:50% 40%}
@media (max-width:760px){
  .sl{grid-template-columns:1fr;min-height:0}
  .sl::before{grid-column:1;grid-row:1;aspect-ratio:1200/630;box-shadow:none;background-position:center}
  .sl-in{grid-column:1;grid-row:2;align-self:start;padding-bottom:4.4rem}
  .sl h2{font-size:clamp(1.5rem,6vw,2rem)}
}

/* ===== photo credits ===== */
.sl::before{background-position:var(--pos,85%) center}
.sl-credit{position:absolute;right:.7rem;bottom:.6rem;z-index:2;max-width:min(60%,24rem);margin:0;font-size:.7rem;line-height:1.3;color:rgba(255,255,255,.92);background:rgba(0,0,0,.55);padding:.25rem .5rem;border-radius:6px}
.sl-credit a{color:#fff}
.cover-fig{margin:1rem 0 0}
.cover-fig .post-cover{margin-top:0}
.cover-fig figcaption{margin-top:.4rem}
.cover-fig figcaption a{color:var(--muted)}
@media (max-width:760px){.sl-credit{position:static;max-width:none;background:none;padding:0 clamp(1.2rem,4vw,2.6rem) 1rem;grid-column:1;grid-row:3;color:rgba(255,255,255,.8)}}