:root{
  --bg:#f5f6f8; --surface:#ffffff; --text:#1c2230; --muted:#5d6678; --line:#e1e4ea;
  --accent:#2f6fed; --accent-ink:#ffffff; --link:#1f55c9; --danger:#d4322c; --shadow:0 2px 10px rgba(20,30,50,.12);
  --radius:10px; --topbar-h:56px;
}
@media (prefers-color-scheme:dark){
  :root{--bg:#12151c; --surface:#1b1f29; --text:#e8ebf2; --muted:#9aa3b5; --line:#2b3140; --link:#8ab0ff; --danger:#ff8a80; --shadow:0 2px 12px rgba(0,0,0,.5);}
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font:16px/1.55 system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;background:var(--bg);color:var(--text)}
a{color:var(--link)}
button,select,input{font:inherit;color:inherit}
button{cursor:pointer}
svg{width:20px;height:20px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;display:block}

/* top bar */
.topbar{height:var(--topbar-h);display:flex;align-items:center;gap:16px;padding:0 16px;background:var(--surface);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:30}
.brand{display:flex;align-items:center;gap:8px;font-weight:700;font-size:1.1rem;color:var(--text);text-decoration:none}
.topnav{display:flex;gap:14px}
.topnav a{color:var(--muted);text-decoration:none;font-size:.92rem}
.topnav a:hover{color:var(--text)}
.topactions{margin-left:auto;display:flex;align-items:center;gap:6px}
.sep{width:1px;height:22px;background:var(--line);margin:0 4px}
.icon-btn{width:36px;height:36px;display:grid;place-items:center;border:0;background:transparent;border-radius:8px}
.icon-btn:hover:not(:disabled){background:var(--bg)}
.icon-btn:disabled{opacity:.35;cursor:default}
.zoom-label{min-width:52px;height:32px;border:0;background:transparent;border-radius:8px;font-size:.9rem;color:var(--muted)}
.zoom-label:hover{background:var(--bg)}
.btn{height:36px;padding:0 14px;border:1px solid var(--line);background:var(--surface);border-radius:8px;font-weight:600;font-size:.92rem}
.btn:hover{background:var(--bg)}
.btn.primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.btn.primary:hover{filter:brightness(1.08)}
.btn.danger{color:var(--danger)}
.btn.wide{width:100%}
.menu-wrap{position:relative}
.menu{position:absolute;right:0;top:42px;min-width:220px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:6px;z-index:50}
.menu button{display:block;width:100%;text-align:left;padding:8px 10px;border:0;background:transparent;border-radius:6px}
.menu button:hover{background:var(--bg)}
.menu hr{border:0;border-top:1px solid var(--line);margin:6px 0}

/* stage */
.stage{position:relative;height:calc(100vh - var(--topbar-h));height:calc(100dvh - var(--topbar-h));min-height:480px;overflow:hidden;background:#fff}
.learn-more{display:flex;align-items:center;justify-content:center;gap:6px;min-height:46px;padding:10px 16px;background:var(--surface);border-top:1px solid var(--line);border-bottom:1px solid var(--line);color:var(--text);text-decoration:none;font-size:.92rem;font-weight:600}
.learn-more:hover{background:var(--bg)}
.skip-link{position:absolute;left:8px;top:-60px;z-index:100;background:var(--accent);color:var(--accent-ink);padding:10px 14px;border-radius:8px;font-weight:600;text-decoration:none}
.skip-link:focus{top:8px}
.sr-only{position:absolute;width:1px;height:1px;margin:-1px;padding:0;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}
#board{position:absolute;inset:0;width:100%;height:100%;touch-action:none;display:block;outline:none;cursor:crosshair}
.toolbar{position:absolute;left:12px;top:56px;z-index:10;display:grid;grid-template-columns:repeat(2,40px);gap:2px;padding:6px;background:var(--surface);border:1px solid var(--line);border-radius:12px;box-shadow:var(--shadow);max-height:calc(100% - 68px);overflow-y:auto;overflow-x:hidden;scrollbar-width:thin}
.tool{width:40px;height:40px;border:0;background:transparent;border-radius:8px;display:grid;place-items:center;color:var(--text)}
.tool:hover{background:var(--bg)}
.tool.active{background:var(--accent);color:var(--accent-ink)}
.tool-label{grid-column:1/-1;white-space:nowrap;font-size:.66rem;letter-spacing:.04em;text-transform:uppercase;color:var(--muted);padding:6px 3px 1px;font-weight:700}
.tool-label:first-child{padding-top:1px}
.popover{position:absolute;z-index:15;min-width:170px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:6px}
.popover[hidden]{display:none}
.popover button{display:block;width:100%;text-align:left;padding:8px 10px;border:0;background:transparent;border-radius:6px}
.popover button:hover{background:var(--bg)}
.menu-title{font-size:.68rem;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);padding:6px 10px 2px;font-weight:700}
.icon-btn.sm{width:30px;height:30px}
.icon-btn.sm svg{width:16px;height:16px}
.boardnav{position:absolute;left:12px;top:12px;z-index:10;display:flex;align-items:center;gap:2px;padding:3px 6px;background:var(--surface);border:1px solid var(--line);border-radius:999px;box-shadow:var(--shadow)}
.pg-label{display:flex;align-items:center;gap:5px;font-size:.84rem;color:var(--muted);padding:0 4px;white-space:nowrap}
.pg-label input{width:42px;height:26px;border:1px solid var(--line);border-radius:6px;background:var(--surface);text-align:center;padding:0}
.timer{position:absolute;left:50%;top:12px;transform:translateX(-50%);z-index:12;background:var(--surface);border:1px solid var(--line);border-radius:14px;box-shadow:var(--shadow);padding:10px 14px;text-align:center}
.timer[hidden]{display:none}
.timer-time{font-size:2.4rem;font-weight:700;font-variant-numeric:tabular-nums;line-height:1.1}
.timer.done .timer-time{color:var(--danger);animation:blink .7s steps(2) infinite}
.timer-row{display:flex;gap:6px;justify-content:center;margin-top:8px}
.timer-row .btn{height:32px;padding:0 12px}
@keyframes blink{50%{opacity:.25}}
body.presenting .topbar,body.presenting .content,body.presenting .footer,body.presenting .ad-slot,body.presenting .statusbar,body.presenting .learn-more,body.presenting .skip-link{display:none}
body.presenting .stage{height:100vh;height:100dvh}
body.presenting .toolbar{max-height:calc(100% - 68px)}

.panel{position:absolute;right:12px;top:12px;width:210px;z-index:10;background:var(--surface);border:1px solid var(--line);border-radius:12px;box-shadow:var(--shadow);padding:12px;max-height:calc(100% - 24px);overflow:auto}
.panel[hidden]{display:none}
.panel-group{margin-bottom:14px}
.panel-group:last-child{margin-bottom:0}
.panel-title{font-size:.72rem;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);margin-bottom:6px;font-weight:700}
.swatches{display:grid;grid-template-columns:repeat(6,1fr);gap:6px}
.swatch{width:100%;aspect-ratio:1;border-radius:50%;border:2px solid var(--line);padding:0}
.swatch.active{outline:2px solid var(--accent);outline-offset:2px}
.custom-color{display:flex;align-items:center;justify-content:space-between;margin-top:8px;font-size:.88rem;color:var(--muted)}
.custom-color input{width:44px;height:28px;padding:0;border:1px solid var(--line);border-radius:6px;background:transparent}
.seg{display:grid;grid-template-columns:repeat(4,1fr);border:1px solid var(--line);border-radius:8px;overflow:hidden}
.seg button{border:0;background:transparent;padding:6px 0;font-weight:600;font-size:.85rem}
.seg button+button{border-left:1px solid var(--line)}
.seg button.active{background:var(--accent);color:var(--accent-ink)}
.check{display:flex;gap:8px;align-items:center;font-size:.92rem}
select{width:100%;height:36px;border:1px solid var(--line);border-radius:8px;background:var(--surface);padding:0 8px}
.inst{display:flex;flex-wrap:wrap;gap:6px}
.chip{border:1px solid var(--line);background:var(--surface);border-radius:999px;padding:5px 11px;font-size:.85rem}
.chip.active{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.hint{font-size:.78rem;color:var(--muted);margin:8px 0 0}
.panel-toggle{position:absolute;right:12px;top:12px;z-index:11;display:none;height:34px;padding:0 12px;border:1px solid var(--line);background:var(--surface);border-radius:999px;box-shadow:var(--shadow);font-weight:600;font-size:.85rem}

.editor{position:absolute;z-index:20;margin:0;padding:2px 4px;border:1.5px dashed var(--accent);background:rgba(255,255,255,.92);color:#111;resize:none;overflow:hidden;font-family:system-ui,sans-serif;outline:none;border-radius:4px;min-width:60px}
.editor[hidden]{display:none}
.toast{position:absolute;left:50%;bottom:48px;transform:translateX(-50%);background:#1c2230;color:#fff;padding:10px 16px;border-radius:8px;font-size:.9rem;z-index:40;max-width:min(560px,90%);box-shadow:var(--shadow)}
.toast[hidden]{display:none}
.statusbar{position:absolute;left:0;right:0;bottom:0;padding:4px 12px;font-size:.74rem;color:#6b7385;background:rgba(255,255,255,.82);text-align:center;pointer-events:none;z-index:5}

.ad-slot{max-width:970px;margin:20px auto;min-height:90px;border:1px dashed var(--line);display:grid;place-items:center;color:var(--muted);font-size:.8rem}
.ad-slot[hidden]{display:none}

/* content */
.content{max-width:900px;margin:0 auto;padding:36px 16px 24px}
.content section[id]{scroll-margin-top:72px}                  /* keep anchor targets clear of the sticky header */
.content h1{font-size:clamp(1.7rem,3.2vw,2.4rem);line-height:1.2;margin:0 0 12px}
.content h2{font-size:1.5rem;margin:36px 0 12px}
.content h3{font-size:1.1rem;margin:20px 0 8px}
.lede{font-size:1.1rem;color:var(--muted)}
.cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:14px;margin-top:20px}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:16px}
.card h3,.content .card h2{font-size:1.1rem;margin:0 0 6px}
.card p{margin:0;color:var(--muted);font-size:.95rem}
.steps li{margin-bottom:8px}
.kbd-list{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:6px 16px;padding:0;list-style:none}
kbd{background:var(--surface);border:1px solid var(--line);border-bottom-width:2px;border-radius:5px;padding:1px 6px;font-size:.85em}
details{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:12px 16px;margin-bottom:8px}
summary{cursor:pointer;font-weight:600}
details p{margin:8px 0 0;color:var(--muted)}
.footer{border-top:1px solid var(--line);padding:20px 16px;text-align:center;color:var(--muted);font-size:.88rem}

@media (max-width:760px){
  .topnav{display:none}
  .topbar{gap:6px;padding:0 8px}
  #btnZoomOut,#btnZoomIn,.sep,.zoom-label{display:none}
  .btn{padding:0 11px;white-space:nowrap}
  .topactions{gap:2px}
  .stage{height:calc(100vh - var(--topbar-h) - 46px);height:calc(100dvh - var(--topbar-h) - 46px)}
  .toolbar{left:50%;top:auto;bottom:8px;transform:translateX(-50%);display:flex;flex-wrap:wrap;justify-content:center;width:min(372px,calc(100% - 12px));overflow:auto;max-height:44vh}
  .tool{flex:0 0 auto;width:40px;height:38px}
  .tool-label{display:none}
  .boardnav{left:6px;top:8px;padding:2px 4px}
  .icon-btn.sm{width:36px;height:36px}
  .pg-label{font-size:.78rem}
  .timer{top:56px}
  .panel-toggle{display:block;top:62px}
  .panel{top:106px;width:min(240px,calc(100% - 24px));max-height:calc(100% - 118px)}
  .statusbar{display:none}
}
@media (max-width:420px){
  .brand span{display:none}
  .pg-word{display:none}
}
/* keyboard focus: always visible, never removed */
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
.tool:focus-visible,.swatch:focus-visible{outline-offset:-2px}
#board:focus-visible{outline:3px solid var(--accent);outline-offset:-3px}
/* touch screens: larger tap targets */
@media (pointer:coarse){
  .toolbar{grid-template-columns:repeat(2,44px)}
  .tool{width:44px;height:44px}
  .icon-btn{width:44px;height:44px}
  .icon-btn.sm{width:40px;height:40px}
  .zoom-label{height:40px}
  .btn{height:42px}
  .chip{padding:9px 14px}
  .seg button{padding:10px 0}
  .menu button,.popover button{padding:12px 12px}
}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .timer.done .timer-time{animation:none}
}