/* Study line — shared theme for the offline Data Science lecture pack.
   Fully offline: fonts are bundled (SIL OFL, see fonts/OFL-*.txt), icons are data: URIs. */

@font-face{font-family:"Fredoka";src:url("fonts/fredoka-latin.woff2") format("woff2");font-weight:300 700;font-display:swap;unicode-range:U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}
@font-face{font-family:"Fredoka";src:url("fonts/fredoka-latin-ext.woff2") format("woff2");font-weight:300 700;font-display:swap;unicode-range:U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C4,U+2113,U+2C60-2C7F,U+A720-A7FF}
@font-face{font-family:"Nunito";src:url("fonts/nunito-latin.woff2") format("woff2");font-weight:200 1000;font-style:normal;font-display:swap;unicode-range:U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}
@font-face{font-family:"Nunito";src:url("fonts/nunito-latin-ext.woff2") format("woff2");font-weight:200 1000;font-style:normal;font-display:swap;unicode-range:U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C4,U+2113,U+2C60-2C7F,U+A720-A7FF}
@font-face{font-family:"Nunito";src:url("fonts/nunito-italic-latin.woff2") format("woff2");font-weight:200 1000;font-style:italic;font-display:swap;unicode-range:U+0000-00FF,U+2000-206F,U+2212}

/* ---------- tokens ---------- */
:root{
  color-scheme:light;
  --bg:#FFF6EC; --bg2:#FCEBDA; --card:#FFFFFF; --card2:#FFF9F2;
  --ink:#2A2238; --ink2:#5E5570; --line:#F0E2D3; --line2:#E3CFBC;
  --link:#1F5FC4;
  --orange:#FF7A3D; --orange-d:#D9541A; --orange-t:#B4461A; --tint-orange:#FFE9DD;
  --green:#2BB673;  --green-d:#178048;  --green-t:#157A45;  --tint-green:#E1F6EA;
  --blue:#4C8DFF;   --blue-d:#2465CC;   --blue-t:#1F5FC4;   --tint-blue:#E5EFFF;
  --sun:#FFC233;    --sun-d:#D99A00;    --sun-t:#8A5D00;    --tint-sun:#FFF1CC;
  --berry:#FF5C8A;  --berry-d:#C7335F;  --berry-t:#B42D57;  --tint-berry:#FFE6EE;
  --lilac:#8C7BFF;  --lilac-d:#6A57E0;  --lilac-t:#5440C9;  --tint-lilac:#EEEBFF;
  --teal:#14B1A1;   --teal-d:#0B7F73;   --teal-t:#0A7469;   --tint-teal:#DDF5F2;
  --red:#F2545B;    --red-d:#C23A41;    --red-t:#B8323A;    --tint-red:#FDE4E5;
  --accent:var(--orange); --accent-d:var(--orange-d); --accent-t:var(--orange-t); --tint:var(--tint-orange);
  --on-bright:#221B30;
  --sky:#FFE3C7; --hill1:#A9E1D6; --hill2:#73CFA0; --hill3:#3DB27D; --cloud:rgba(255,255,255,.9);
  --shadow:0 1px 0 rgba(42,34,56,.03),0 10px 28px -16px rgba(42,34,56,.28);
  --r:22px;
  --font-d:"Fredoka",ui-rounded,"SF Pro Rounded","Arial Rounded MT Bold","Trebuchet MS",system-ui,sans-serif;
  --font-b:"Nunito",ui-rounded,"SF Pro Rounded",system-ui,-apple-system,"Segoe UI",sans-serif;
  --font-m:ui-monospace,"SF Mono",Menlo,Consolas,"Liberation Mono",monospace;
  --top:60px;
}
html[data-theme=dark]{
  color-scheme:dark;
  --bg:#18141F; --bg2:#211B2C; --card:#241E31; --card2:#2B243A; --ink:#F7F0E8; --ink2:#C2B8D0; --line:#362E47; --line2:#463C5B;
  --link:#94BCFF;
  --orange-t:#FFA372; --tint-orange:#3B2620;
  --green-t:#6FE0A2;  --tint-green:#173527;
  --blue-t:#94BCFF;   --tint-blue:#1B2944;
  --sun-t:#FFD36B;    --tint-sun:#3A2F17;
  --berry-t:#FF93B3;  --tint-berry:#3D1D30;
  --lilac-t:#BDB2FF;  --tint-lilac:#28224A;
  --teal-t:#62DFD1;   --tint-teal:#11332F;
  --red-t:#FF8E93;    --tint-red:#401E24;
  --orange-d:#B9461A; --green-d:#13703F; --sun-d:#B98300; --berry-d:#A82A50; --lilac-d:#5444BD; --teal-d:#0A6C62; --blue-d:#1E52A6; --red-d:#A3333A;
  --sky:#2B2347; --hill1:#2E4A5E; --hill2:#2C5A4C; --hill3:#22463A; --cloud:rgba(255,255,255,.12);
  --shadow:0 1px 0 rgba(0,0,0,.2),0 12px 30px -16px rgba(0,0,0,.6);
}
body[data-unit=a]{--accent:var(--teal);--accent-d:var(--teal-d);--accent-t:var(--teal-t);--tint:var(--tint-teal)}
body[data-unit=b]{--accent:var(--orange);--accent-d:var(--orange-d);--accent-t:var(--orange-t);--tint:var(--tint-orange)}
body[data-unit=c]{--accent:var(--lilac);--accent-d:var(--lilac-d);--accent-t:var(--lilac-t);--tint:var(--tint-lilac)}
body[data-unit=d]{--accent:var(--blue);--accent-d:var(--blue-d);--accent-t:var(--blue-t);--tint:var(--tint-blue)}

/* ---------- base ---------- */
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%;text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:400 17.5px/1.68 var(--font-b);
  background-image:radial-gradient(60vmax 40vmax at 110% -10%,var(--tint) 0,transparent 60%),radial-gradient(50vmax 40vmax at -20% 30%,var(--bg2) 0,transparent 60%);
  background-attachment:fixed;min-height:100vh;-webkit-font-smoothing:antialiased}
[hidden]{display:none!important}
html:not(.js) .needs-js{display:none!important}
.sr{position:absolute!important;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}
main{max-width:760px;margin:0 auto;padding:8px 20px 96px}
@media (max-width:560px){main{padding:4px 14px 80px}.chunk{padding:18px 16px 6px}.hero{padding:22px 18px 20px}}
main.home{max-width:1180px}
[id]{scroll-margin-top:calc(var(--top) + 16px)}
h1,h2,h3,h4{font-family:var(--font-d);font-weight:600;line-height:1.2;letter-spacing:-.005em;color:var(--ink);text-wrap:balance}
h1{font-size:clamp(32px,8.4vw,52px);line-height:1.06;margin:.15em 0 .35em}
h2{font-size:clamp(22px,5.6vw,27px);margin:1.6em 0 .55em}
h3{font-size:20px;margin:1.4em 0 .4em}
p,li{text-wrap:pretty}
p{margin:0 0 .9em}
strong{font-weight:800}
a{color:var(--link);text-decoration-thickness:2px;text-underline-offset:3px;text-decoration-color:color-mix(in srgb,currentColor 35%,transparent)}
a:hover{text-decoration-color:currentColor}
:focus-visible{outline:3px solid var(--blue);outline-offset:3px;border-radius:12px}
ul,ol{padding-left:1.3em;margin:0 0 1em}
li{margin:.3em 0}
li::marker{color:var(--accent-t);font-weight:800}
img,svg{max-width:100%;height:auto}
hr{border:0;height:44px;margin:4px auto;background:radial-gradient(circle,var(--line2) 3px,transparent 3.5px) center/14px 14px repeat-y;width:14px}
.eyebrow{font:600 13px/1.4 var(--font-d);letter-spacing:.09em;text-transform:uppercase;color:var(--accent-t);margin:0 0 .3em}
.muted{color:var(--ink2);font-size:15px}
.small{font-size:14px}
.count{font-variant-numeric:tabular-nums}
output{display:inline-block;font:600 1em var(--font-d);color:var(--accent-t);font-variant-numeric:tabular-nums}
::selection{background:color-mix(in srgb,var(--sun) 55%,transparent)}

/* ---------- icons ---------- */
.ic{display:inline-block;flex:none;width:1.15em;height:1.15em;vertical-align:-.18em;background:currentColor;-webkit-mask:var(--i) center/contain no-repeat;mask:var(--i) center/contain no-repeat}
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fill='black'/%3E%3C/svg%3E");--i-check:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M5 12.5l4.5 4.5L19 7.5' stroke-width='3.2'/%3E%3C/svg%3E");--i-x:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M6.5 6.5l11 11M17.5 6.5l-11 11' stroke-width='3.2'/%3E%3C/svg%3E");--i-arrow:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M5 12h14M13 6l6 6-6 6'/%3E%3C/svg%3E");--i-back:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M19 12H5M11 6l-6 6 6 6'/%3E%3C/svg%3E");--i-chev:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M6 9.5l6 6 6-6' stroke-width='2.6'/%3E%3C/svg%3E");--i-clock:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Ccircle cx='12' cy='12' r='9'/%3E%3Cpath d='M12 7v5l3.2 2'/%3E%3C/svg%3E");--i-slides:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Crect x='3' y='4' width='18' height='12.5' rx='2.5'/%3E%3Cpath d='M12 16.5V20M8 20.5h8'/%3E%3C/svg%3E");--i-sliders:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M4 7h9M18 7h2M4 17h3M12 17h8'/%3E%3Ccircle cx='15.5' cy='7' r='2.5'/%3E%3Ccircle cx='9.5' cy='17' r='2.5'/%3E%3C/svg%3E");--i-target:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Ccircle cx='12' cy='12' r='9'/%3E%3Ccircle cx='12' cy='12' r='5'/%3E%3Ccircle cx='12' cy='12' r='1.3' fill='black'/%3E%3C/svg%3E");--i-lock:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Crect x='5' y='11' width='14' height='10' rx='2.5'/%3E%3Cpath d='M8 11V8a4 4 0 0 1 8 0v3'/%3E%3C/svg%3E");--i-download:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M12 4v11M7 10.5l5 5 5-5M5 20h14'/%3E%3C/svg%3E");--i-sparkle:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M12 2.5c.8 4.6 2.9 6.7 7.5 7.5-4.6.8-6.7 2.9-7.5 7.5-.8-4.6-2.9-6.7-7.5-7.5 4.6-.8 6.7-2.9 7.5-7.5z' fill='black'/%3E%3Cpath d='M19 16.5c.3 1.6 1 2.3 2.5 2.5-1.5.3-2.2 1-2.5 2.5-.3-1.5-1-2.2-2.5-2.5 1.5-.2 2.2-.9 2.5-2.5z' fill='black' stroke-width='1.2'/%3E%3C/svg%3E");--i-alert:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M12 3.5 2.5 20h19z'/%3E%3Cpath d='M12 10v4.5M12 17.5v.01' stroke-width='2.6'/%3E%3C/svg%3E");--i-calc:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Crect x='5' y='3' width='14' height='18' rx='2.5'/%3E%3Cpath d='M8.5 7.5h7M8.5 12h.01M12 12h.01M15.5 12h.01M8.5 16h.01M12 16h.01M15.5 16h.01' stroke-width='2.6'/%3E%3C/svg%3E");--i-eye:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M2 12s3.6-6.5 10-6.5S22 12 22 12s-3.6 6.5-10 6.5S2 12 2 12z'/%3E%3Ccircle cx='12' cy='12' r='3'/%3E%3C/svg%3E");--i-book:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M3 5.5c3-1.3 6-1.3 9 .5 3-1.8 6-1.8 9-.5V19c-3-1.3-6-1.3-9 .5-3-1.8-6-1.8-9-.5z'/%3E%3Cpath d='M12 6v13.5'/%3E%3C/svg%3E");--i-question:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Ccircle cx='12' cy='12' r='9.5'/%3E%3Cpath d='M9.3 9.3a2.8 2.8 0 1 1 3.9 2.6c-.8.4-1.2 1-1.2 1.9v.4M12 17h.01' stroke-width='2.4'/%3E%3C/svg%3E");--i-flag:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M5.5 21V4M5.5 4.5h11l-2.2 4 2.2 4h-11'/%3E%3C/svg%3E");--i-pencil:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M4 20l1-4.5L15.5 5a2.1 2.1 0 0 1 3 3L8 18.5z'/%3E%3Cpath d='M13.5 7l3 3'/%3E%3C/svg%3E");--i-map:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='black' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M9 4 3 6.5v13.5L9 17.5l6 2.5 6-2.5V4l-6 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d='M18 50c26-12 58-12 84 0l-1.5 11c-26-11-55-11-81 0z' fill='%2314B1A1'/%3E%3Cpath d='M100.5 51l13-7-2.5 13zM100 56l14 3-11 6z' fill='%230E8A7D'/%3E%3Ccircle cx='37' cy='79' r='6.5' fill='%23FF5C8A' opacity='.35'/%3E%3Ccircle cx='83' cy='79' r='6.5' fill='%23FF5C8A' opacity='.35'/%3E%3Cpath d='M41 69q6-7 12 0M67 69q6-7 12 0' stroke='%232A2238' stroke-width='4.5' fill='none' stroke-linecap='round'/%3E%3Cpath d='M50 78h20q-1 12-10 12t-10-12z' fill='%232A2238'/%3E%3Cpath d='M54 86q6-4 12 0q-2 4-6 4t-6-4z' fill='%23FF5C8A'/%3E%3Cpath d='M14 24l3 7M8 34l7 1M106 24l-3 7M112 34l-7 1' stroke='%23FFC233' stroke-width='4' stroke-linecap='round'/%3E%3C/svg%3E");--m-oops:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 120 120'%3E%3Cellipse cx='60' cy='113' rx='30' ry='4.5' fill='%232A2238' opacity='.12'/%3E%3Cellipse cx='45' cy='104' rx='11' ry='7' fill='%23D9541A'/%3E%3Cellipse cx='75' cy='104' rx='11' ry='7' fill='%23D9541A'/%3E%3Cpath d='M60 22c26 0 44 17 44 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html[data-theme=dark]{--i-chev-ink:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' stroke='%23C2B8D0' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round' fill='none'%3E%3Cpath d='M6 9.5l6 6 6-6' stroke-width='2.6'/%3E%3C/svg%3E")}
.ic-home{--i:var(--i-home)}
.ic-bolt{--i:var(--i-bolt)}
.ic-flame{--i:var(--i-flame)}
.ic-check{--i:var(--i-check)}
.ic-x{--i:var(--i-x)}
.ic-arrow{--i:var(--i-arrow)}
.ic-back{--i:var(--i-back)}
.ic-chev{--i:var(--i-chev)}
.ic-clock{--i:var(--i-clock)}
.ic-slides{--i:var(--i-slides)}
.ic-sliders{--i:var(--i-sliders)}
.ic-target{--i:var(--i-target)}
.ic-lock{--i:var(--i-lock)}
.ic-download{--i:var(--i-download)}
.ic-sparkle{--i:var(--i-sparkle)}
.ic-alert{--i:var(--i-alert)}
.ic-calc{--i:var(--i-calc)}
.ic-eye{--i:var(--i-eye)}
.ic-book{--i:var(--i-book)}
.ic-question{--i:var(--i-question)}
.ic-flag{--i:var(--i-flag)}
.ic-pencil{--i:var(--i-pencil)}
.ic-map{--i:var(--i-map)}
.ic-bulb{--i:var(--i-bulb)}
.ic-play{--i:var(--i-play)}
.ic-moon{--i:var(--i-moon)}
.ic-sun{--i:var(--i-sun)}
.ic-list{--i:var(--i-list)}
.ic-l1{--i:var(--i-l1)}
.ic-l2{--i:var(--i-l2)}
.ic-l3{--i:var(--i-l3)}
.ic-l4{--i:var(--i-l4)}
.ic-l5{--i:var(--i-l5)}
.ic-l6{--i:var(--i-l6)}
.ic-l7{--i:var(--i-l7)}
.ic-l8{--i:var(--i-l8)}
.ic-l9{--i:var(--i-l9)}
.mascot{display:inline-block;flex:none;width:56px;height:56px;background:var(--m-happy) center/contain no-repeat}
.mascot.cheer{background-image:var(--m-cheer)}
.mascot.oops{background-image:var(--m-oops)}

/* ---------- chips & buttons ---------- */
.chip{display:inline-flex;align-items:center;gap:6px;padding:5px 12px;border-radius:999px;background:var(--card);border:2px solid var(--line);font:600 15px/1.2 var(--font-d);color:var(--ink);white-space:nowrap;font-variant-numeric:tabular-nums}
.chip.xp .ic{color:var(--sun-d)}
.chip.streak .ic{color:var(--orange)}
.chip.streak.cold .ic{color:var(--ink2);opacity:.6}
.btn,.selfcheck button,.step-done button,.paper-done button{-webkit-appearance:none;appearance:none;display:inline-flex;align-items:center;justify-content:center;gap:.5em;min-height:50px;padding:12px 22px;border-radius:16px;border:0;cursor:pointer;
  font:700 19px/1.15 var(--font-d);letter-spacing:.01em;text-decoration:none;color:var(--on-bright);background:var(--green);box-shadow:0 5px 0 var(--green-d);
  transition:transform .09s ease,box-shadow .09s ease,filter .2s,background-color .2s;margin:0}
.btn:hover,.selfcheck button:hover,.step-done button:hover,.paper-done button:hover{filter:brightness(1.06) saturate(1.05)}
.btn:active,.selfcheck button:active,.step-done button:active,.paper-done button:active{transform:translateY(5px);box-shadow:0 0 0 var(--green-d)}
.btn.soft,.selfcheck button.soft{background:var(--card);color:var(--ink);box-shadow:0 5px 0 var(--line2);border:2px solid var(--line2)}
.btn.soft:active,.selfcheck button.soft:active{box-shadow:0 0 0 var(--line2)}
.btn.sun{background:var(--sun);box-shadow:0 5px 0 var(--sun-d)}
.btn.small{min-height:40px;padding:8px 14px;font-size:16px;border-radius:13px}

/* ---------- top bar ---------- */
.topbar{position:sticky;top:0;z-index:20;background:color-mix(in srgb,var(--bg) 86%,transparent);-webkit-backdrop-filter:blur(14px) saturate(1.4);backdrop-filter:blur(14px) saturate(1.4);border-bottom:2px solid var(--line);padding-top:env(safe-area-inset-top)}
.topbar-in{max-width:760px;margin:0 auto;display:flex;align-items:center;gap:12px;height:var(--top);padding:0 16px}
.home .topbar-in,body[data-page=home] .topbar-in{max-width:1180px}
.tb-home{flex:none;display:grid;place-items:center;width:44px;height:44px;border-radius:14px;background:var(--card);border:2px solid var(--line2);box-shadow:0 4px 0 var(--line2);color:var(--ink);text-decoration:none;transition:transform .09s,box-shadow .09s}
.tb-home:active{transform:translateY(4px);box-shadow:0 0 0 var(--line2)}
.tb-home .ic{width:22px;height:22px}
.brand{display:flex;align-items:center;gap:10px;font:600 19px/1 var(--font-d);color:var(--ink);text-decoration:none;margin-right:auto}
.brand .mascot{width:40px;height:40px}
.tb-steps{flex:1;display:flex;gap:6px;min-width:0}
.tb-steps a{flex:1;display:block;height:36px;position:relative;border-radius:10px}
.tb-steps a::before{content:"";position:absolute;left:0;right:0;top:12px;height:12px;border-radius:99px;background:var(--line);transition:background-color .35s}
.tb-steps a.done::before{background:var(--green);box-shadow:inset 0 -3px 0 rgba(0,0,0,.12)}
.tb-steps a.here::before{outline:2px solid var(--accent);outline-offset:2px}
.tb-steps a.done::after{content:"";position:absolute;left:8px;right:auto;top:14px;width:30%;height:3px;border-radius:9px;background:rgba(255,255,255,.55)}
.tb-stats{display:flex;gap:8px;margin-left:auto;flex:none}
.tb-theme + .tb-stats{margin-left:0}
.tb-theme{-webkit-appearance:none;appearance:none;flex:none;margin-left:auto;display:grid;place-items:center;width:40px;height:40px;border-radius:13px;border:2px solid var(--line);background:var(--card);color:var(--ink2);cursor:pointer;padding:0}
.tb-theme:hover{color:var(--ink);border-color:var(--line2)}
.tb-theme .ic{width:20px;height:20px}
.tb-theme .ic-sun,[data-theme=dark] .tb-theme .ic-moon{display:none}
[data-theme=dark] .tb-theme .ic-sun{display:inline-block}
@media (max-width:380px){.topbar-in{gap:8px;padding:0 10px}.tb-stats{gap:6px}.chip{padding:5px 9px}}
.tb-spacer{flex:1}
.readbar{height:3px;background:transparent;overflow:hidden}
.readbar span{display:block;height:100%;width:100%;background:var(--accent);transform-origin:0 50%;transform:scaleX(0)}

/* ---------- hero (lesson & content pages) ---------- */
.hero{position:relative;margin:22px 0 10px;padding:26px 22px 24px;border-radius:30px;background:var(--tint);overflow:hidden;isolation:isolate;display:flex;flex-direction:column}
.hero::before,.hero::after{content:"";position:absolute;z-index:-1;border-radius:50%;background:var(--accent);opacity:.13}
.hero::before{width:260px;height:260px;right:-90px;top:-110px}
.hero::after{width:150px;height:150px;right:70px;bottom:-95px;opacity:.09}
.hero h1{margin:.12em 0 .25em;max-width:20ch}
.hero + .lead,.hero + .chunk{margin-top:22px}
.hero .eyebrow{order:-1}
.hero-badge{order:-2;width:64px;height:64px;border-radius:50%;background:var(--accent);box-shadow:0 6px 0 var(--accent-d);display:grid;place-items:center;color:#fff;margin-bottom:14px}
.hero-badge .ic{width:32px;height:32px}
.hero-meta{display:flex;flex-wrap:wrap;gap:8px;margin:8px 0 0}
.hero-meta .chip{background:color-mix(in srgb,var(--card) 80%,transparent);border-color:transparent}
.hero > nav{order:-1;display:flex;flex-wrap:wrap;gap:8px;margin:0 0 10px}
.hero > nav a{display:inline-flex;align-items:center;gap:6px;padding:6px 13px;border-radius:999px;background:color-mix(in srgb,var(--card) 85%,transparent);font:600 15px/1.3 var(--font-d);color:var(--ink);text-decoration:none;border:2px solid transparent}
.hero > nav a:hover{border-color:var(--accent)}
.hero .lead{font-size:18px;color:var(--ink2);max-width:58ch}
@media (min-width:700px){
  .hero{padding:36px 40px 32px}
  .hero-badge{position:absolute;right:34px;top:32px;width:84px;height:84px;margin:0}
  .hero-badge .ic{width:42px;height:42px}
  .hero h1,.hero .lead{padding-right:100px}
}

/* ---------- lesson menu (original .toc nav) ---------- */
.lesson-menu{display:grid;gap:14px;margin:18px 0 26px}
.lesson-menu .back{justify-self:start;display:inline-flex;align-items:center;gap:6px;font:600 16px var(--font-d);color:var(--ink2);text-decoration:none;padding:4px 2px}
.lesson-menu .back:hover{color:var(--ink)}
.step-tiles{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px}
.tile{position:relative;display:flex;flex-direction:column;align-items:flex-start;gap:4px;padding:14px 12px 12px;border-radius:20px;background:var(--card);border:2px solid var(--line2);box-shadow:0 5px 0 var(--line2);color:var(--ink);text-decoration:none;transition:transform .09s,box-shadow .09s,background-color .3s,border-color .3s}
.tile:active{transform:translateY(5px);box-shadow:0 0 0 var(--line2)}
.tile-n{display:grid;place-items:center;width:30px;height:30px;border-radius:50%;background:var(--accent);color:#fff;font:700 16px var(--font-d);box-shadow:0 3px 0 var(--accent-d)}
.tile-t{font:600 17px/1.15 var(--font-d);margin-top:4px}
.tile-m{font-size:13px;color:var(--ink2);line-height:1.2}
.tile.done{background:var(--tint-green);border-color:var(--green);box-shadow:0 5px 0 var(--green-d)}
.tile.done .tile-n{background:var(--green);box-shadow:0 3px 0 var(--green-d);color:transparent;position:relative}
.tile.done .tile-n::after{content:"";position:absolute;inset:6px;background:var(--on-bright);-webkit-mask:var(--i-check) center/contain no-repeat;mask:var(--i-check) center/contain no-repeat}
.res{display:flex;flex-wrap:wrap;gap:8px}
.res a{display:inline-flex;align-items:center;gap:7px;padding:8px 14px;border-radius:14px;background:var(--card);border:2px solid var(--line);font:600 15.5px/1.2 var(--font-d);color:var(--ink);text-decoration:none}
.res a:hover{border-color:var(--accent)}
.res a .ic{color:var(--accent-t)}
.res a.hot{background:var(--sun);border-color:var(--sun);color:var(--on-bright);box-shadow:0 4px 0 var(--sun-d)}
.res a.hot .ic{color:var(--on-bright)}

/* ---------- steps & chunks ---------- */
article.step{position:relative}
.step-kicker{display:flex;align-items:center;gap:10px;font:600 14px/1.3 var(--font-d);letter-spacing:.08em;text-transform:uppercase;color:var(--accent-t);margin:24px 0 0}
.step-kicker .dot{display:grid;place-items:center;width:28px;height:28px;border-radius:50%;background:var(--accent);color:#fff;letter-spacing:0;font-size:15px;box-shadow:0 3px 0 var(--accent-d)}
.step-kicker .time{margin-left:auto;display:inline-flex;align-items:center;gap:5px;color:var(--ink2);letter-spacing:.02em;text-transform:none;font-weight:500}
.chunk{background:var(--card);border:2px solid var(--line);border-radius:var(--r);padding:20px 20px 8px;margin:16px 0;box-shadow:var(--shadow)}
.chunk > h2:first-child,.chunk > h3:first-child{margin-top:0}
.chunk > h2{display:flex;gap:10px;align-items:flex-start}
.chunk > h2 .h2-ic{width:28px;height:28px;margin-top:-1px;color:var(--accent-t)}
.chunk.intro{background:none;border:0;box-shadow:none;padding:4px 2px 0;margin:6px 0 10px}
.chunk.intro > h2{font-size:clamp(30px,7.6vw,40px);margin:.1em 0 .35em}
.chunk.intro > p:first-of-type{font-size:18px}
.chunk.coverage{background:var(--card2);box-shadow:none;border-style:dashed}
.chunk.coverage,.chunk.coverage p{font-size:15.5px;color:var(--ink2)}
.chunk.next{background:var(--tint-blue);border-color:transparent;box-shadow:none}
.chunk.next .h2-ic{color:var(--blue-t)}
.chunk.cando{background:var(--tint-green);border-color:transparent;box-shadow:none}
.chunk.cando .h2-ic{color:var(--green-t)}
.chunk.cando p{font-size:18px;font-weight:600}
.chunk.keep{background:var(--tint-sun);border-color:transparent}
.chunk.keep .h2-ic{color:var(--sun-t)}
.chunk.tryit{background:var(--tint-lilac);border-color:transparent;box-shadow:none}
.chunk.tryit .h2-ic{color:var(--lilac-t)}
.chunk.confusions{background:var(--tint-berry);border-color:transparent;box-shadow:none}
.chunk.confusions .h2-ic{color:var(--berry-t)}
.chunk.confusions ul{list-style:none;padding:0}
.chunk.confusions li{position:relative;padding:10px 12px 10px 46px;margin:8px 0;background:color-mix(in srgb,var(--card) 75%,transparent);border-radius:14px}
.chunk.confusions li::before{content:"";position:absolute;left:12px;top:12px;width:24px;height:24px;border-radius:50%;background:var(--berry) var(--i-x-w) center/14px no-repeat}
.chunk-tools{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin:-2px 0 12px}
.chunk-tools .hint-text{font-size:14px;color:var(--ink2)}

/* the ideas to keep */
.chunk.ideas{background:var(--card);padding-bottom:16px}
@media (max-width:759px){.chunk.ideas{background:none;border:0;box-shadow:none;padding:4px 0 0}.chunk.ideas .idea{background:var(--card);box-shadow:var(--shadow)}}
.chunk.ideas .idea{position:relative;margin:10px 0;padding:14px 16px 14px 18px;border-radius:18px;background:var(--card2);border:2px solid var(--line);border-left:7px solid var(--c,var(--accent));font-size:16.5px;line-height:1.6;transition:color .25s,text-shadow .25s,background-color .25s}
.chunk.ideas .idea > strong:first-child{display:block;font:600 19px/1.25 var(--font-d);color:var(--ct,var(--accent-t));margin-bottom:3px}
.idea:nth-of-type(6n+1){--c:var(--teal);--ct:var(--teal-t)}
.idea:nth-of-type(6n+2){--c:var(--orange);--ct:var(--orange-t)}
.idea:nth-of-type(6n+3){--c:var(--lilac);--ct:var(--lilac-t)}
.idea:nth-of-type(6n+4){--c:var(--berry);--ct:var(--berry-t)}
.idea:nth-of-type(6n+5){--c:var(--blue);--ct:var(--blue-t)}
.idea:nth-of-type(6n+6){--c:var(--sun-d);--ct:var(--sun-t)}
@media (min-width:760px){
  .chunk.ideas{display:grid;grid-template-columns:1fr 1fr;column-gap:12px}
  .chunk.ideas > :not(.idea){grid-column:1/-1}
  .chunk.ideas .idea{margin:6px 0}
}
.recall .idea{color:transparent;text-shadow:0 0 9px color-mix(in srgb,var(--ink) 55%,transparent);cursor:pointer;user-select:none}
.recall .idea code{color:transparent;background:none}
.recall .idea > strong:first-child{text-shadow:none}
.recall .idea.revealed{color:var(--ink);text-shadow:none;cursor:auto;user-select:auto}
.recall .idea:not(.revealed)::after{content:"Tap to reveal";position:absolute;right:12px;bottom:10px;font:600 12px var(--font-d);letter-spacing:.04em;color:var(--ink2);text-shadow:none;background:var(--card);padding:2px 8px;border-radius:99px;border:1.5px solid var(--line2)}

/* callouts */
.callout{position:relative;padding:14px 16px 14px 54px;border-radius:18px;background:var(--cbg);margin:16px 0}
.callout::before{content:"";position:absolute;left:14px;top:15px;width:28px;height:28px;border-radius:9px;background:var(--cfg) var(--ci) center/17px no-repeat}
.callout > strong:first-child{color:var(--ct)}
.callout.correction{--cbg:var(--tint-berry);--cfg:var(--berry);--ct:var(--berry-t);--ci:var(--i-alert-w)}
.callout.exam{--cbg:var(--tint-sun);--cfg:var(--sun-d);--ct:var(--sun-t);--ci:var(--i-flag-w)}
.callout.worked{--cbg:var(--tint-blue);--cfg:var(--blue-d);--ct:var(--blue-t);--ci:var(--i-calc-w)}
.callout.illus{--cbg:transparent;--cfg:var(--lilac-d);--ct:var(--lilac-t);--ci:var(--i-pencil-w);border:2px dashed color-mix(in srgb,var(--lilac) 55%,transparent)}
strong.examnote{color:var(--sun-t);background:var(--tint-sun);padding:0 .3em;border-radius:6px}
.formula{font:500 18px/1.55 var(--font-m);color:var(--ink);text-align:center;padding:16px 14px;margin:14px 0;border-radius:16px;background:var(--tint);border:2px solid color-mix(in srgb,var(--accent) 35%,transparent);overflow-x:auto;white-space:nowrap}

/* tables, code, figures */
.table-wrap{overflow-x:auto;margin:16px 0;border-radius:18px;border:2px solid var(--line);background:var(--card);-webkit-overflow-scrolling:touch}
table{border-collapse:collapse;width:100%;font-size:15px;line-height:1.5}
th,td{padding:10px 13px;text-align:left;vertical-align:top;border-bottom:1.5px solid var(--line)}
th{font:600 15px/1.3 var(--font-d);background:var(--tint);color:var(--ink);white-space:nowrap}
td:first-child{font-weight:700}
tbody tr:last-child td{border-bottom:0}
tbody tr:nth-child(even) td{background:color-mix(in srgb,var(--card2) 60%,transparent)}
@media (max-width:520px){table{font-size:14.5px} th,td{padding:9px 10px} th{white-space:normal}}
pre{background:#231C33;color:#F6EFE6;border-radius:18px;padding:16px 18px;overflow-x:auto;font:14px/1.6 var(--font-m);margin:14px 0;box-shadow:inset 0 0 0 2px rgba(255,255,255,.04)}
[data-theme=dark] pre{background:#120E1A}
code{font-family:var(--font-m);font-size:.86em}
:not(pre) > code{background:var(--tint-lilac);color:var(--lilac-t);padding:.12em .38em;border-radius:7px;font-weight:600;overflow-wrap:break-word}
td code,th code{overflow-wrap:normal;white-space:pre-wrap}
pre code{background:none;color:inherit;padding:0;font-weight:400}
.figure{margin:16px 0;background:#fff;border-radius:18px;padding:10px;border:2px solid var(--line)}
.figure img{display:block;margin:0 auto;border-radius:10px}
main img:not(.figure img){border-radius:14px}

/* details / summary */
details{margin:14px 0;border-radius:18px;background:var(--card2);border:2px solid var(--line)}
summary{list-style:none;cursor:pointer;display:flex;align-items:center;gap:10px;padding:13px 16px;font:600 17px/1.3 var(--font-d);border-radius:16px;color:var(--ink)}
summary::-webkit-details-marker{display:none}
summary::after{content:"";margin-left:auto;flex:none;width:22px;height:22px;background:currentColor;-webkit-mask:var(--i-chev) center/contain no-repeat;mask:var(--i-chev) center/contain no-repeat;transition:transform .25s}
details[open] > summary::after{transform:rotate(180deg)}
details > :not(summary){margin-left:16px;margin-right:16px}
details > :nth-child(2){margin-top:4px}
details[open]{padding-bottom:4px}
.answer{background:var(--card);border-color:var(--line2);box-shadow:0 5px 0 var(--line2)}
.answer > summary{color:var(--blue-t)}
.answer > summary .ic{color:var(--blue-t)}
.answer[open]{box-shadow:none;border-color:var(--blue);background:var(--tint-blue)}
.answer[open] > summary{border-bottom:2px solid color-mix(in srgb,var(--blue) 30%,transparent);border-radius:16px 16px 0 0;margin-bottom:12px}
.jump{background:var(--card)}
.jump ol{columns:2 220px;column-gap:18px;padding-left:1.4em;font-size:15px}
.jump li{break-inside:avoid;margin:.15em 0 .35em}

/* practice cards */
.chunk.qcard{border:2px solid var(--line2);box-shadow:0 6px 0 var(--line2);padding-bottom:16px}
.qbadge{display:block;width:max-content;font:600 13px/1 var(--font-d);letter-spacing:.09em;text-transform:uppercase;color:var(--accent-t);background:var(--tint);padding:7px 11px;border-radius:99px;margin:0 0 10px}
.qcard > h2{display:block}
.qcard > h2 > .qbadge{margin-bottom:10px}
.qdash{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.qcard > p:not(.muted){font-size:17.5px}
.selfcheck{display:flex;flex-wrap:wrap;align-items:center;gap:12px;margin:14px 0 2px;padding:14px;border-radius:18px;background:var(--card2);border:2px dashed var(--line2)}
.selfcheck p{margin:0;flex:1 1 100%;font:600 16px var(--font-d);color:var(--ink2)}
.selfcheck button{min-height:44px;font-size:17px;padding:8px 18px;flex:1 1 auto}
.selfcheck.rated{border-style:solid;border-color:var(--green);background:var(--tint-green)}
.selfcheck.rated.miss{border-color:var(--sun-d);background:var(--tint-sun)}
.selfcheck button[aria-pressed=true]{outline:3px solid var(--ink);outline-offset:2px}

/* step done */
.step-done{display:flex;flex-wrap:wrap;align-items:center;gap:14px;margin:22px 0 8px;padding:18px;border-radius:24px;background:var(--card);border:2px solid var(--line);box-shadow:var(--shadow)}
.step-done .mascot{width:58px;height:58px}
.step-done p{margin:0;flex:1 1 180px;font:600 18px/1.3 var(--font-d)}
.step-done p span{display:block;font:400 15px/1.4 var(--font-b);color:var(--ink2);margin-top:3px}
.step-done button{flex:1 1 100%}
.step-done button .xpg,.paper-done button .xpg{font-size:15px;padding:3px 9px;border-radius:99px;background:rgba(255,255,255,.4)}
.step-done button.done,.paper-done button.done{background:var(--card);color:var(--green-t);box-shadow:0 5px 0 var(--line2);border:2px solid var(--green)}
@media (min-width:600px){.step-done button{flex:0 1 auto}}

.lesson-foot{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:36px 0 0}
.lesson-foot a{display:flex;flex-direction:column;gap:2px;padding:14px 16px;border-radius:20px;background:var(--card);border:2px solid var(--line2);box-shadow:0 5px 0 var(--line2);color:var(--ink);text-decoration:none;font:600 16px/1.25 var(--font-d)}
.lesson-foot a small{font:600 12.5px var(--font-d);letter-spacing:.08em;text-transform:uppercase;color:var(--ink2)}
.lesson-foot a.next{text-align:right;align-items:flex-end}
.lesson-foot a:only-child{grid-column:1/-1}
.lesson-foot a:active{transform:translateY(5px);box-shadow:0 0 0 var(--line2)}

/* ---------- generic content pages / explore ---------- */
section,.panel{display:block}
.lab,.panel{background:var(--card);border:2px solid var(--line);border-radius:26px;padding:20px;margin:18px 0;box-shadow:var(--shadow)}
.lab > h2:first-child,.lab-kicker + h2{margin-top:0}
.lab-kicker{display:inline-flex;align-items:center;gap:7px;font:600 13px var(--font-d);letter-spacing:.08em;text-transform:uppercase;color:var(--lilac-t);background:var(--tint-lilac);padding:6px 11px;border-radius:99px;margin:0 0 12px}
.hint{position:relative;padding:14px 16px 14px 54px;border-radius:18px;background:var(--tint-teal);margin:16px 0;color:var(--ink)}
.hint::before{content:"";position:absolute;left:14px;top:15px;width:28px;height:28px;border-radius:9px;background:var(--teal-d) var(--i-bulb-w) center/17px no-repeat}
label{display:block;font:600 16.5px/1.35 var(--font-d);margin:16px 0 6px;color:var(--ink)}
label:has(input[type=checkbox]){display:flex;align-items:center;gap:10px;font-weight:500;padding:10px 12px;border-radius:14px;background:var(--card2);border:2px solid var(--line);cursor:pointer}
input[type=checkbox]{width:24px;height:24px;accent-color:var(--green);flex:none;margin:0}
input[type=number],select{font:600 17px var(--font-d);color:var(--ink);background:var(--card2);border:2px solid var(--line2);border-radius:14px;padding:10px 12px;width:100%;max-width:100%;min-height:48px}
select{max-width:320px;-webkit-appearance:none;appearance:none;padding-right:40px;background:var(--card2) var(--i-chev-ink) right 12px center/20px no-repeat}
input[type=number]:focus,select:focus{border-color:var(--blue);outline:none;box-shadow:0 0 0 3px color-mix(in srgb,var(--blue) 30%,transparent)}
input[type=range]{-webkit-appearance:none;appearance:none;width:100%;height:36px;background:transparent;margin:4px 0 10px;cursor:pointer}
input[type=range]::-webkit-slider-runnable-track{height:14px;border-radius:99px;background:linear-gradient(var(--line2),var(--line2));box-shadow:inset 0 2px 0 rgba(0,0,0,.08)}
input[type=range]::-moz-range-track{height:14px;border-radius:99px;background:var(--line2)}
input[type=range]::-moz-range-progress{height:14px;border-radius:99px;background:var(--accent)}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:34px;height:34px;margin-top:-10px;border-radius:50%;background:var(--card);border:3px solid var(--accent);box-shadow:0 4px 0 var(--accent-d)}
input[type=range]::-moz-range-thumb{width:28px;height:28px;border-radius:50%;background:var(--card);border:3px solid var(--accent);box-shadow:0 4px 0 var(--accent-d)}
input[type=range]:focus-visible{outline:none}
input[type=range]:focus-visible::-webkit-slider-thumb{outline:3px solid var(--blue);outline-offset:2px}
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:12px;margin:12px 0}
@media (max-width:560px){.grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
.grid label{margin-top:0}
.metric{padding:14px 14px 12px;border-radius:18px;background:var(--card2);border:2px solid var(--line);font:600 14px/1.3 var(--font-d);color:var(--ink2);letter-spacing:.02em}
.metric strong{display:block;font:600 clamp(22px,6vw,28px)/1.15 var(--font-d);color:var(--accent-t);margin-top:4px;font-variant-numeric:tabular-nums;overflow-wrap:anywhere}
.metric:nth-child(4n+2) strong{color:var(--lilac-t)}
.metric:nth-child(4n+3) strong{color:var(--berry-t)}
.metric:nth-child(4n+4) strong{color:var(--blue-t)}
#plot,#bars,#clusters,#scales,#hrPlot,#heartPlot{margin:12px 0;border-radius:18px;overflow:hidden;background:#fff;border:2px solid var(--line)}
#plot svg,#bars svg,#clusters svg,#scales svg,#hrPlot svg,#heartPlot svg{display:block;width:100%}
#bars{padding:8px 6px 0}
.lab button{-webkit-appearance:none;appearance:none;display:inline-flex;align-items:center;justify-content:center;min-height:46px;padding:10px 18px;margin:6px 8px 6px 0;border-radius:15px;border:2px solid var(--line2);background:var(--card);color:var(--ink);box-shadow:0 5px 0 var(--line2);font:600 17px/1.2 var(--font-d);cursor:pointer;transition:transform .09s,box-shadow .09s}
.lab button:active{transform:translateY(5px);box-shadow:0 0 0 var(--line2)}
.lab button#step,.lab button#rare{background:var(--green);border-color:var(--green);color:var(--on-bright);box-shadow:0 5px 0 var(--green-d)}
.lab button#step:active,.lab button#rare:active{box-shadow:0 0 0 var(--green-d)}
.lead{font-size:18.5px;line-height:1.6}
.content-chunk{background:var(--card);border:2px solid var(--line);border-radius:var(--r);padding:20px 20px 6px;margin:16px 0;box-shadow:var(--shadow)}
.content-chunk > h2:first-child{margin-top:0}
ol.timeline{list-style:none;padding:0;counter-reset:tl;position:relative}
ol.timeline li{counter-increment:tl;position:relative;padding:4px 0 14px 54px;margin:0}
ol.timeline li::before{content:counter(tl);position:absolute;left:0;top:0;width:38px;height:38px;border-radius:50%;display:grid;place-items:center;font:700 18px var(--font-d);color:#fff;background:var(--c);box-shadow:0 4px 0 var(--cd)}
ol.timeline li::after{content:"";position:absolute;left:17px;top:44px;bottom:2px;width:4px;border-radius:4px;background:var(--line2)}
ol.timeline li:last-child::after{display:none}
ol.timeline li:nth-child(5n+1){--c:var(--teal);--cd:var(--teal-d)}
ol.timeline li:nth-child(5n+2){--c:var(--lilac);--cd:var(--lilac-d)}
ol.timeline li:nth-child(5n+3){--c:var(--orange);--cd:var(--orange-d)}
ol.timeline li:nth-child(5n+4){--c:var(--berry);--cd:var(--berry-d)}
ol.timeline li:nth-child(5n+5){--c:var(--green);--cd:var(--green-d)}

/* ---------- home ---------- */
.home-grid{display:grid;gap:18px;grid-template-columns:minmax(0,1fr);align-items:start}
.home-hero{position:relative;margin:18px 0 0}
.home-hero h1{font-size:clamp(36px,10vw,54px);margin:.1em 0 .3em;max-width:13ch}
.home-hero .lead{color:var(--ink2);max-width:46ch}
.scene{display:block;width:100%;max-width:520px;margin:6px 0 0;filter:drop-shadow(0 18px 24px rgba(42,34,56,.12))}
.scene .night{display:none}
[data-theme=dark] .scene .day{display:none}[data-theme=dark] .scene .night{display:inline}
.dash{background:var(--card);border:2px solid var(--line);border-radius:28px;padding:20px;box-shadow:var(--shadow);display:grid;gap:16px}
.countdown{display:flex;align-items:center;gap:16px}
.cd-big{flex:none;display:grid;place-items:center;width:92px;height:92px;border-radius:26px;background:var(--berry);box-shadow:0 6px 0 var(--berry-d);color:#fff;text-align:center;line-height:1}
.cd-big b{display:block;font:700 42px/1 var(--font-d);letter-spacing:-.02em}
.cd-big small{display:block;font:600 13px var(--font-d);letter-spacing:.06em;text-transform:uppercase;margin-top:2px}
.cd-txt strong{display:block;font:600 21px/1.2 var(--font-d)}
.cd-txt span{display:block;color:var(--ink2);font-size:15px;line-height:1.4;margin-top:3px}
.stats{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px}
.stat{padding:12px 10px 10px;border-radius:18px;background:var(--card2);border:2px solid var(--line);text-align:center;min-width:0}
.stat .ic{width:26px;height:26px}
.stat b{display:block;font:700 24px/1.1 var(--font-d);font-variant-numeric:tabular-nums;margin-top:4px}
.stat small{display:block;font:600 12.5px/1.3 var(--font-d);color:var(--ink2);letter-spacing:.02em}
.stat.xp .ic{color:var(--sun-d)} .stat.streak .ic{color:var(--orange)} .stat.goal .ic{color:var(--green)}
.stat.streak.cold .ic{color:var(--ink2);opacity:.5}
.week{display:flex;justify-content:center;gap:4px;margin-top:6px}
.week i{width:9px;height:9px;border-radius:50%;background:var(--line2)}
.week i.on{background:var(--orange)}
.week i.today{outline:2px solid var(--ink2);outline-offset:1px}
.goalbar{height:9px;border-radius:99px;background:var(--line);margin-top:8px;overflow:hidden}
.goalbar span{display:block;height:100%;width:calc(var(--p,0)*100%);background:var(--green);border-radius:99px;transition:width .6s cubic-bezier(.2,.8,.2,1)}
.dash .btn{width:100%}
.dash .btn small{font:600 14px var(--font-b);opacity:.85}
.commute{position:relative;background:var(--tint-sun);border-radius:28px;padding:22px 20px 14px;overflow:hidden}
.commute > h2{margin:0 0 12px;padding-right:70px}
.commute > .mascot{position:absolute;right:16px;top:14px;width:64px;height:64px}
.routine{display:flex;flex-direction:column;align-items:flex-start;gap:0;font-weight:700;margin:2px 0 4px}
.routine .r{display:inline-block;padding:5px 11px;border-radius:12px;font:600 15.5px/1.3 var(--font-d);color:var(--on-bright)}
.routine .r1{background:var(--teal)} .routine .r2{background:var(--lilac)} .routine .r3{background:var(--orange)} .routine .r4{background:var(--green)}
.routine .arr{display:block;color:var(--ink2);font-weight:600;transform:rotate(90deg);width:1em;margin:1px 0 1px 14px;line-height:1.1}
@media (min-width:600px){.routine{flex-direction:row;flex-wrap:wrap;align-items:center;gap:6px}.routine .arr{transform:none;margin:0}}
.commute .links{display:flex;flex-wrap:wrap;gap:8px;align-items:center}
.commute .links a{display:inline-flex;align-items:center;padding:8px 14px;border-radius:14px;background:var(--card);border:2px solid var(--line2);box-shadow:0 4px 0 var(--line2);font:600 15.5px var(--font-d);color:var(--ink);text-decoration:none}
.commute .links a:active{transform:translateY(4px);box-shadow:0 0 0 var(--line2)}
.commute .links .sep{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}
.path-head{display:flex;flex-wrap:wrap;align-items:baseline;justify-content:space-between;gap:4px 12px;margin:26px 0 10px}
.path-head h2{margin:0;font-size:clamp(26px,6.4vw,34px)}
.path-head p{margin:0;color:var(--ink2);font-size:15px}
.line{position:relative;padding:4px 0 0}
.line > *{position:relative}
.line > *::before{content:"";position:absolute;left:39px;top:0;bottom:0;width:10px;background:var(--u);z-index:0}
.line > :first-child::before{top:50%}
.line .unit-banner::before{left:39px}
.line .terminus::before{bottom:50%}
.line > .ua{--u:var(--teal);--ud:var(--teal-d);--ut:var(--teal-t);--utint:var(--tint-teal)}
.line > .ub{--u:var(--orange);--ud:var(--orange-d);--ut:var(--orange-t);--utint:var(--tint-orange)}
.line > .uc{--u:var(--lilac);--ud:var(--lilac-d);--ut:var(--lilac-t);--utint:var(--tint-lilac)}
.line > .ue{--u:var(--berry);--ud:var(--berry-d);--ut:var(--berry-t);--utint:var(--tint-berry)}
.unit-banner{margin:0;padding:18px 0}
.unit-banner > span{position:relative;z-index:1;display:block;margin-left:0;padding:14px 18px;border-radius:20px;background:var(--u);color:var(--on-bright);box-shadow:0 5px 0 var(--ud);font:600 19px/1.2 var(--font-d)}
.unit-banner > span small{display:block;font:500 14.5px/1.35 var(--font-b);opacity:.85;margin-top:2px}
.station{display:flex;align-items:center;gap:12px;padding:9px 0;color:var(--ink);text-decoration:none;-webkit-tap-highlight-color:transparent}
.node{position:relative;z-index:1;flex:none;width:88px;height:88px;display:grid;place-items:center}
.ring{position:absolute;inset:0;width:88px;height:88px;transform:rotate(-90deg)}
.ring circle{fill:none;stroke-width:6.5}
.ring .rb{stroke:color-mix(in srgb,var(--u) 22%,var(--bg))}
.ring .rf{stroke:var(--sun);stroke-linecap:round;stroke-dasharray:100;stroke-dashoffset:calc(100 - var(--p,0) * 100);transition:stroke-dashoffset 1s cubic-bezier(.2,.8,.2,1)}
.disc{display:grid;place-items:center;width:64px;height:64px;border-radius:50%;background:var(--u);box-shadow:0 6px 0 var(--ud);color:#fff;transition:transform .12s,box-shadow .12s}
.disc .ic{width:30px;height:30px}
.station:hover .disc{transform:translateY(-2px);box-shadow:0 8px 0 var(--ud)}
.station:active .disc{transform:translateY(6px);box-shadow:0 0 0 var(--ud)}
.station.done .disc{background:var(--sun);box-shadow:0 6px 0 var(--sun-d);color:var(--on-bright)}
.station.done .ring .rf{stroke:var(--green)}
.st-txt{flex:1;min-width:0;padding:12px 14px;border-radius:18px;background:var(--card);border:2px solid var(--line);box-shadow:var(--shadow);transition:border-color .2s}
.station:hover .st-txt{border-color:var(--u)}
.st-txt strong{display:block;font:600 18.5px/1.2 var(--font-d);color:var(--ink)}
.st-txt > span{display:block;font-size:14px;line-height:1.4;color:var(--ink2);margin-top:3px}
.st-badges{display:flex;flex-wrap:wrap;gap:6px;margin-top:8px}
.st-badges:empty{display:none}
.st-badges b{font:600 12.5px/1 var(--font-d);padding:5px 8px;border-radius:99px;background:var(--utint);color:var(--ut);letter-spacing:.02em}
.st-badges b.ok{background:var(--tint-green);color:var(--green-t)}
.bubble{position:absolute;z-index:2;left:50%;top:-14px;transform:translateX(-50%);white-space:nowrap;font:700 12px/1 var(--font-d);letter-spacing:.08em;text-transform:uppercase;padding:6px 9px;border-radius:10px;background:var(--card);color:var(--ut);border:2px solid var(--u);animation:bob 2.2s ease-in-out infinite}
.bubble::after{content:"";position:absolute;left:50%;bottom:-6px;width:9px;height:9px;background:var(--card);border-right:2px solid var(--u);border-bottom:2px solid var(--u);transform:translateX(-50%) rotate(45deg)}
.station.next .disc{animation:pulse 2.2s ease-in-out infinite}
.terminus{display:flex;align-items:center;gap:12px;padding:12px 0 4px}
.terminus .disc{background:var(--berry);box-shadow:0 6px 0 var(--berry-d)}
.terminus .st-txt{background:var(--tint-berry);border-color:transparent}
.offline,.vault{margin:22px 0}
.offline{background:var(--card);border:2px solid var(--line);border-radius:26px;padding:20px 20px 8px;box-shadow:var(--shadow)}
.offline h2{margin-top:0;display:flex;gap:10px;align-items:center}
.offline h2 .ic{color:var(--teal-t)}
.vault{background:var(--card);border:2px solid var(--line2);box-shadow:0 5px 0 var(--line2)}
.vault > summary{padding:16px 18px}
.vault > summary .ic{color:var(--sun-d);width:24px;height:24px}
.home-foot{display:flex;flex-wrap:wrap;gap:10px;align-items:center;justify-content:space-between;color:var(--ink2);font-size:14px;margin:28px 0 0}
@media (min-width:980px){
  .home-grid{grid-template-columns:minmax(0,1fr) minmax(0,1.05fr);column-gap:44px}
  .home-grid > *{grid-column:1}
  .home-grid > .path{grid-column:2;grid-row:1 / span 6}
  .home-hero{margin-top:30px}
  .path-head{margin-top:36px}
}

/* ---------- quiz pages (question bank, literature) ---------- */
.toc.chips{display:flex;flex-wrap:wrap;gap:8px;margin:14px 0 18px}
.toc.chips a{display:inline-flex;align-items:center;gap:6px;padding:7px 12px;border-radius:13px;background:var(--card);border:2px solid var(--line);font:600 15px/1.2 var(--font-d);color:var(--ink);text-decoration:none}
.toc.chips a:hover{border-color:var(--accent)}
.toc.chips a .mini{font-size:12.5px;padding:2px 6px;border-radius:99px;background:var(--tint-green);color:var(--green-t)}
.toc.chips a .mini:empty{display:none}
.toc.chips a.done{border-color:var(--green);background:var(--tint-green)}
.score{position:fixed;left:50%;bottom:calc(14px + env(safe-area-inset-bottom));transform:translateX(-50%);z-index:30;display:flex;width:max-content;max-width:calc(100% - 32px);align-items:center;gap:8px;margin:0;padding:8px 14px;border-radius:99px;background:var(--ink);color:var(--bg);font:600 15px/1.2 var(--font-d);box-shadow:0 8px 20px -10px rgba(0,0,0,.5)}
.score:empty{display:none}
.qset-head{margin:30px 0 8px}
.qset-head h2{margin:0 0 4px}
.setbar{height:12px;border-radius:99px;background:var(--line);overflow:hidden;margin:10px 0 4px}
.setbar span{display:block;height:100%;width:calc(var(--p,0)*100%);background:var(--green);border-radius:99px;transition:width .6s cubic-bezier(.2,.8,.2,1);box-shadow:inset 0 -3px 0 rgba(0,0,0,.12)}
.setscore{margin:0;font:600 14.5px var(--font-d);color:var(--ink2)}
.q{position:relative;background:var(--card);border:2px solid var(--line2);border-radius:24px;padding:18px 18px 8px;margin:18px 0;box-shadow:0 6px 0 var(--line2)}
.q h3{margin:0 0 8px;font:600 14px/1.35 var(--font-d);letter-spacing:.05em;text-transform:uppercase;color:var(--accent-t);padding-right:54px}
.q .stem{font-size:18px;line-height:1.55;font-weight:600;margin:0 0 12px}
.q .tag{display:inline-block;font:600 11.5px/1 var(--font-d);letter-spacing:.05em;padding:4px 7px;border-radius:99px;background:var(--tint-sun);color:var(--sun-t);margin-left:8px;vertical-align:1px}
.q .was{position:absolute;right:14px;top:14px;font:700 11.5px/1 var(--font-d);letter-spacing:.05em;text-transform:uppercase;padding:5px 8px;border-radius:99px}
.q .was.ok{background:var(--tint-green);color:var(--green-t)}
.q .was.no{background:var(--tint-red);color:var(--red-t)}
.opts{list-style:none;padding:0;margin:0 0 6px;display:grid;gap:10px}
.opts li{margin:0}
.opts button{-webkit-appearance:none;appearance:none;width:100%;display:flex;align-items:flex-start;gap:12px;text-align:left;padding:12px 14px;border-radius:16px;background:var(--card);color:var(--ink);border:2px solid var(--line2);box-shadow:0 4px 0 var(--line2);font:500 16.5px/1.45 var(--font-b);cursor:pointer;transition:transform .09s,box-shadow .09s,background-color .2s,border-color .2s,opacity .3s}
.opts button:hover{border-color:var(--blue);background:var(--tint-blue)}
.opts button:active{transform:translateY(4px);box-shadow:0 0 0 var(--line2)}
.opts .L{flex:none;display:grid;place-items:center;width:30px;height:30px;border-radius:10px;border:2px solid var(--line2);font:700 15px/1 var(--font-d);color:var(--ink2);margin-top:-2px;transition:background-color .2s,color .2s,border-color .2s}
.opts button.right{background:var(--tint-green);border-color:var(--green);box-shadow:0 4px 0 var(--green-d);animation:pop .45s cubic-bezier(.3,1.6,.5,1)}
.opts button.right .L{background:var(--green);border-color:var(--green);color:transparent;-webkit-mask:none;position:relative}
.opts button.right .L::after{content:"";position:absolute;inset:5px;background:var(--on-bright);-webkit-mask:var(--i-check) center/contain no-repeat;mask:var(--i-check) center/contain no-repeat}
.opts button.wrong{background:var(--tint-red);border-color:var(--red);box-shadow:0 4px 0 var(--red-d);animation:shake .4s}
.opts button.wrong .L{background:var(--red);border-color:var(--red);color:#fff}
.q.answered .opts button{cursor:default}
.q.answered .opts button:not(.right):not(.wrong){opacity:.55}
.q.answered .opts button:hover:not(.right):not(.wrong){background:var(--card);border-color:var(--line2)}
.fb{display:flex;align-items:center;gap:12px;margin:12px 0 4px;padding:10px 14px;border-radius:16px;font:600 17px/1.3 var(--font-d)}
.fb:empty{display:none}
.fb .mascot{width:44px;height:44px}
.fb.ok{background:var(--tint-green);color:var(--green-t)}
.fb.no{background:var(--tint-red);color:var(--red-t)}
.fb .xpg{margin-left:auto;font-size:14px;padding:4px 9px;border-radius:99px;background:var(--sun);color:var(--on-bright);white-space:nowrap}
.q details{margin:12px 0 10px}
.q details > summary{font-size:16px;padding:11px 14px}
.q.open-q .selfcheck{margin-bottom:10px}
.intro-hint{background:var(--tint-sun);border-radius:18px;padding:14px 16px;margin:14px 0}

.paper{background:var(--card);border:2px solid var(--line);border-radius:28px;margin:30px 0;box-shadow:var(--shadow);overflow:hidden}
.paper-head{background:var(--tint-lilac);padding:20px 20px 16px;position:relative}
.paper-head .eyebrow{font:600 13.5px/1.45 var(--font-b);color:var(--ink2);text-transform:none;letter-spacing:0;margin-bottom:10px}
.paper-head h2{margin:.15em 0 .4em;font-size:clamp(22px,5.4vw,27px)}
.paper-head .muted{margin:0}
.paper-type{display:inline-block;font:600 12.5px/1.2 var(--font-d);padding:5px 9px;border-radius:99px;background:var(--card);color:var(--lilac-t);margin:0 0 10px}
.paper-body{padding:16px 20px 18px}
.paper-body > h3{font-size:18px;margin:1.3em 0 .35em;color:var(--lilac-t)}
.oneline{font-size:18px;line-height:1.5;margin:4px 0 14px}
.story{position:relative;margin:8px 0 14px;padding-left:30px}
.story::before{content:"";position:absolute;left:9px;top:10px;bottom:10px;width:4px;border-radius:4px;background:linear-gradient(var(--teal),var(--lilac),var(--orange),var(--green))}
.beat{position:relative;margin:0 0 12px}
.beat::before{content:"";position:absolute;left:-29px;top:4px;width:18px;height:18px;border-radius:50%;background:var(--card);border:4px solid var(--bc)}
.beat:nth-child(1){--bc:var(--teal)} .beat:nth-child(2){--bc:var(--lilac)} .beat:nth-child(3){--bc:var(--orange)} .beat:nth-child(4){--bc:var(--green)}
.beat h3{margin:0 0 2px;font-size:15px;letter-spacing:.07em;text-transform:uppercase;color:var(--ink2)}
.beat p,.beat ul{margin:0 0 4px}
.remember{background:var(--tint-sun);border-radius:18px;padding:12px 16px 4px;margin:16px 0}
.remember h3{margin:0 0 4px;color:var(--sun-t);font-size:17px}
.paper-done{display:flex;justify-content:center;margin:18px 0 4px}
.paper-done button{width:100%}

/* ---------- feedback layer ---------- */
.toast{position:fixed;z-index:60;left:0;right:0;margin:0 auto;width:max-content;bottom:calc(18px + env(safe-area-inset-bottom));transform:translateY(160%);display:flex;align-items:center;gap:12px;max-width:calc(100% - 32px);padding:10px 18px 10px 10px;border-radius:22px;background:var(--ink);color:var(--bg);font:600 17px/1.3 var(--font-d);box-shadow:0 18px 40px -12px rgba(0,0,0,.45);transition:transform .45s cubic-bezier(.3,1.4,.5,1);pointer-events:none}
.toast.show{transform:none}
.toast .mascot{width:46px;height:46px}
.toast small{display:block;font:500 14px var(--font-b);opacity:.8}
.xpfloat{position:fixed;z-index:61;pointer-events:none;font:700 20px var(--font-d);color:var(--sun-d);text-shadow:0 2px 0 var(--card);animation:floatup 1.1s ease-out forwards}
.confetti{position:fixed;z-index:59;pointer-events:none;width:10px;height:14px;border-radius:3px;animation:confetti var(--d,1s) cubic-bezier(.15,.6,.4,1) forwards}
@keyframes floatup{0%{opacity:0;transform:translate(-50%,6px) scale(.8)}15%{opacity:1;transform:translate(-50%,-6px) scale(1.15)}100%{opacity:0;transform:translate(-50%,-64px) scale(1)}}
@keyframes confetti{0%{opacity:1;transform:translate(0,0) rotate(0)}100%{opacity:0;transform:translate(var(--x),var(--y)) rotate(var(--r))}}
@keyframes pop{0%{transform:scale(1)}40%{transform:scale(1.035)}100%{transform:scale(1)}}
@keyframes shake{0%,100%{transform:translateX(0)}20%{transform:translateX(-7px)}40%{transform:translateX(6px)}60%{transform:translateX(-4px)}80%{transform:translateX(3px)}}
@keyframes bob{0%,100%{transform:translate(-50%,0)}50%{transform:translate(-50%,-5px)}}
@keyframes pulse{0%,100%{box-shadow:0 6px 0 var(--ud),0 0 0 0 color-mix(in srgb,var(--u) 45%,transparent)}50%{box-shadow:0 6px 0 var(--ud),0 0 0 12px transparent}}
@keyframes rise{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}
.js .home-grid > *,.js .hero,.js .lesson-menu{animation:rise .6s cubic-bezier(.2,.8,.2,1) both}
.js .home-grid > :nth-child(2){animation-delay:.07s}.js .home-grid > :nth-child(3){animation-delay:.14s}.js .home-grid > :nth-child(4){animation-delay:.2s}
.js .lesson-menu{animation-delay:.08s}

@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation:none!important;transition:none!important}
}
@media print{
  body{background:#fff}
  .topbar,.needs-js,.step-done,.selfcheck,.toast,.lesson-foot{display:none!important}
  main{max-width:100%;padding:0}
  .chunk,.lab,.q,.paper{box-shadow:none;break-inside:avoid-page}
  details{break-inside:avoid}
}
.chunk.outro{background:none;border:0;box-shadow:none;padding:4px 4px 0;font-size:15.5px}

@media (max-width:560px){.callout,.hint{padding-left:16px}.callout::before,.hint::before{position:static;float:left;margin:1px 10px 0 0}}

/* cross-device sync (web) */
.sync-ui{padding:0 18px 18px}
.sync-ui p{margin:0 0 12px}
.sync-code{font:700 18px var(--font-d);letter-spacing:.06em;white-space:nowrap}
.sync-join{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.sync-join input{font:600 17px var(--font-d);color:var(--ink);background:var(--card2);border:2px solid var(--line2);border-radius:14px;padding:10px 12px;min-height:48px;flex:1 1 160px;max-width:100%;letter-spacing:.04em}
.sync-join input:focus{border-color:var(--blue);outline:none;box-shadow:0 0 0 3px color-mix(in srgb,var(--blue) 30%,transparent)}
.sync-status{color:var(--ink2);font-size:14px;min-height:1em}

/* rewritten notes: math, figures, key lines */
.math-display{overflow-x:auto;overflow-y:hidden;margin:16px 0;padding:6px 0;text-align:center}
math{font-size:1.08em;font-family:"STIX Two Math","Latin Modern Math","Cambria Math",math}
.math-display math{font-size:1.15em}
.figure img[src$=".svg"],p.figure img[src$=".svg"]{display:block;width:100%;max-width:560px;height:auto;margin:6px auto 0;border-radius:16px}
.figcap{color:var(--ink2);font-size:14px;text-align:center;margin-top:6px}
.callout.inshort{background:var(--tint-teal);border-left:5px solid var(--teal);border-radius:12px;padding:12px 16px;font-weight:600}
.callout.heard{background:var(--tint-lilac);border-left:5px solid var(--lilac);border-radius:12px;padding:12px 16px}

/* ---------- listen mode (assets/tts.js) ---------- */
.tts-sec{position:relative}
.tts-sec > h2,.tts-sec .paper-head > .eyebrow{padding-right:54px}
.tts-btn,.tts-main,.tts-x,.tts-pbtn{-webkit-appearance:none;appearance:none;display:inline-grid;place-items:center;flex:none;margin:0;padding:0;cursor:pointer;font:600 15px/1 var(--font-d);color:var(--ink);background:var(--card);border:2px solid var(--line2);transition:transform .09s ease,box-shadow .09s ease,background-color .2s}
.tts-btn svg,.tts-main svg,.tts-x svg,.tts-pbtn svg{width:22px;height:22px;grid-area:1/1}
.tts-btn .s,.tts-player .s{fill:none;stroke:currentColor;stroke-width:2.4;stroke-linecap:round}
.tts-btn{position:absolute;top:13px;right:14px;width:44px;height:44px;border-radius:50%;color:var(--accent-t);box-shadow:0 4px 0 var(--line2)}
.tts-btn:active,.tts-pbtn:active,.tts-main:active,.tts-x:active{transform:translateY(4px);box-shadow:0 0 0 var(--line2)}
.tts-btn:hover{border-color:var(--accent)}
.tts-btn svg + svg,.tts-btn.on svg,.tts-btn.wait svg{visibility:hidden}
.tts-btn.on svg:nth-child(2),.tts-btn.wait svg:nth-child(3){visibility:visible}
.tts-btn.on,.tts-btn.wait{background:var(--accent);border-color:var(--accent);color:var(--on-bright);box-shadow:0 4px 0 var(--accent-d)}
.tts-btn.wait,.tts-main.wait{animation:tts-pulse 1.1s ease-in-out infinite}
@keyframes tts-pulse{50%{opacity:.55}}
.chunk.intro > .tts-btn{top:2px;right:0}
.paper-head > .tts-btn{top:14px;right:14px}
@media (max-width:759px){.chunk.ideas > .tts-btn{top:2px;right:0}}
@media (max-width:560px){.tts-btn{top:10px;right:10px}.chunk.intro > .tts-btn{top:0;right:0}}
.tts-on{outline:3px solid color-mix(in srgb,var(--accent) 75%,transparent);outline-offset:4px}
.chunk.tts-on{outline-offset:2px}

.tts-player{position:fixed;z-index:50;left:0;right:0;bottom:calc(12px + env(safe-area-inset-bottom));margin:0 auto;width:min(560px,calc(100% - 24px));
  display:grid;grid-template-columns:auto 1fr auto;align-items:center;gap:4px 12px;padding:12px;border-radius:24px;overflow:hidden;
  background:var(--card);border:2px solid var(--line2);box-shadow:0 18px 40px -14px rgba(42,34,56,.5);animation:tts-up .35s cubic-bezier(.2,.9,.3,1.2)}
@keyframes tts-up{from{transform:translateY(130%)}}
.tts-dl{position:absolute;left:0;right:0;top:0;height:4px;background:var(--line)}
.tts-dl span{display:block;height:100%;width:0;background:var(--teal);transition:width .3s}
.tts-main{grid-row:1/3;width:56px;height:56px;border-radius:50%;background:var(--accent);border-color:var(--accent);color:var(--on-bright);box-shadow:0 4px 0 var(--accent-d)}
.tts-main svg{width:26px;height:26px}
.tts-main:active{box-shadow:0 0 0 var(--accent-d)}
.tts-info{min-width:0;display:flex;flex-direction:column;gap:2px}
.tts-title{font:600 16.5px/1.25 var(--font-d);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.tts-status{font-size:13.5px;line-height:1.3;color:var(--ink2);white-space:nowrap;overflow:hidden;text-overflow:ellipsis;font-variant-numeric:tabular-nums}
.tts-x{width:44px;height:44px;border-radius:14px;border-color:transparent;background:none;color:var(--ink2)}
.tts-x:hover{color:var(--ink);background:var(--card2)}
.tts-ctrl{grid-column:2/4;display:flex;flex-wrap:wrap;gap:8px}
.tts-pbtn{min-width:44px;height:44px;padding:0 12px;border-radius:14px;box-shadow:0 3px 0 var(--line2);display:inline-flex;gap:6px;align-items:center}
.tts-pbtn svg{width:20px;height:20px}
.tts-auto[aria-pressed=false]{color:var(--ink2);border-style:dashed;box-shadow:none}
.tts-auto[aria-pressed=true]{background:var(--tint);border-color:var(--accent);color:var(--accent-t)}
@media (max-width:420px){.tts-player{gap:4px 10px;padding:10px}.tts-pbtn{padding:0 9px}.tts-auto span{font-size:14px}}
body.tts-open main{padding-bottom:calc(170px + env(safe-area-inset-bottom))}
body.tts-open .score{bottom:calc(150px + env(safe-area-inset-bottom))}
.tts-toast{bottom:calc(150px + env(safe-area-inset-bottom));padding:12px 18px;font-size:16px}

.tts-sheet{width:min(460px,calc(100% - 24px));max-height:calc(100% - 24px);margin:auto auto calc(12px + env(safe-area-inset-bottom));padding:20px;border-radius:26px;
  border:2px solid var(--line2);background:var(--card);color:var(--ink);box-shadow:0 24px 60px -18px rgba(0,0,0,.55)}
@media (min-width:600px){.tts-sheet{margin:auto}}
.tts-sheet::backdrop{background:rgba(24,20,31,.45)}
.tts-sheet h2{margin:0 0 14px;font-size:22px}
.tts-opt{display:flex;flex-direction:column;align-items:flex-start;gap:4px;width:100%;margin:0 0 14px;text-align:left;font-size:18px}
.tts-opt small{font:500 14.5px/1.4 var(--font-b);opacity:.85}
.tts-opt[aria-current=true] b::after{content:" · current";font-weight:500;font-size:14px}
.tts-sheet .muted{margin:2px 0 12px;font-size:14px}
.tts-cancel{width:100%}
@media print{.tts-btn,.tts-player{display:none!important}}
/* open questions: your answer + compare */
.myanswer{margin:14px 0 10px}
.myanswer label{display:block;font:700 15px var(--font-d);color:var(--ink);margin:0 0 6px}
.myanswer textarea{display:block;width:100%;max-width:100%;min-height:110px;resize:vertical;font:500 16px/1.5 var(--font-b,inherit);color:var(--ink);background:var(--card2);border:2px solid var(--line2);border-radius:14px;padding:12px 14px;box-sizing:border-box}
.myanswer textarea:focus{border-color:var(--blue);outline:none;box-shadow:0 0 0 3px color-mix(in srgb,var(--blue) 30%,transparent)}
.ma-row{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-top:8px;flex-wrap:wrap}
.ma-saved{color:var(--ink2);font-size:14px;min-height:1em}
.ma-compare{margin:10px 0 4px}
.ma-h{font:700 14px var(--font-d);text-transform:uppercase;letter-spacing:.06em;color:var(--ink2);margin:14px 0 6px}
.ma-h small{text-transform:none;letter-spacing:0;font-weight:500}
.ma-compare blockquote{margin:0;padding:12px 14px;background:var(--card2);border-left:5px solid var(--blue);border-radius:12px;white-space:normal}
.ma-points{list-style:none;padding:0;margin:0}
.ma-points li{padding:8px 12px;border-radius:12px;margin:6px 0;background:var(--card2)}
.ma-points li.hit{background:var(--tint-green)}
.ma-points li.hit span{color:var(--green-t);font-weight:800}
.ma-points li.miss span{color:var(--ink2)}
.ma-points small{color:var(--ink2)}
.rubric-h{font:700 14px var(--font-d);text-transform:uppercase;letter-spacing:.06em;color:var(--ink2);margin:14px 0 6px}
.rubric{list-style:none;padding:0;margin:0 0 8px}
.rubric li{padding:8px 12px;border-radius:12px;margin:6px 0;background:var(--card2);border:2px solid var(--line)}
.rubric li b,.ma-points li b{color:var(--orange-t);margin-right:4px}