:root{
  --paper:#F5F6FA; --surface:#FFFFFF; --ink:#1C2142; --muted:#596080; --line:#D5D9E8;
  --accent:#3442A6; --accent-ink:#FFFFFF; --hatch:#3442A6; --mark:#1C2142;
  --good:#1D7550; --good-tint:#E3F3EB; --bad:#B42318; --bad-tint:rgba(180,35,24,.16); --bad-bg:#FBE9E7;
  --soft:#ECEEF7;
  --serif:'Literata', Georgia, 'Times New Roman', serif;
  --sans:'Atkinson Hyperlegible', system-ui, -apple-system, 'Segoe UI', Arial, sans-serif;
  color-scheme: light;
  box-sizing:border-box;
  padding-top:env(safe-area-inset-top,0px);
  padding-bottom:env(safe-area-inset-bottom,0px);
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --paper:#11132A; --surface:#1A1D39; --ink:#E7E9F7; --muted:#A2A8C8; --line:#323759;
    --accent:#8F9CFF; --accent-ink:#11132A; --hatch:#8F9CFF; --mark:#E7E9F7;
    --good:#5FCB9C; --good-tint:#16352B; --bad:#FF8F84; --bad-tint:rgba(255,143,132,.2); --bad-bg:#3A1E22;
    --soft:#232747; color-scheme: dark;
  }
}
:root[data-theme="dark"]{
  --paper:#11132A; --surface:#1A1D39; --ink:#E7E9F7; --muted:#A2A8C8; --line:#323759;
  --accent:#8F9CFF; --accent-ink:#11132A; --hatch:#8F9CFF; --mark:#E7E9F7;
  --good:#5FCB9C; --good-tint:#16352B; --bad:#FF8F84; --bad-tint:rgba(255,143,132,.2); --bad-bg:#3A1E22;
  --soft:#232747; color-scheme: dark;
}
html{scroll-padding-top:env(safe-area-inset-top,0px)}
*,*::before,*::after{box-sizing:border-box}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--sans);font-size:17px;line-height:1.5;-webkit-tap-highlight-color:transparent}
main{max-width:640px;margin:0 auto;padding:20px 18px 64px}
h1,h2,h3{font-family:var(--serif);font-weight:600;line-height:1.2;margin:0}
h1{font-size:2.4rem;letter-spacing:-.01em}
h2{font-size:1.55rem}
h3{font-size:1.1rem}
p{margin:.4em 0}
.muted{color:var(--muted)}
button{font:inherit;color:inherit;cursor:pointer}
button:focus-visible,select:focus-visible,a:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
.back{background:none;border:0;padding:6px 0;color:var(--accent);font-weight:700;margin-bottom:10px}

/* Home */
.hero{display:flex;align-items:center;gap:16px;margin:8px 0 6px}
.hero svg{width:92px;height:auto;flex:none}
.tagline{font-size:1.05rem;color:var(--muted);max-width:30ch}
.levels{list-style:none;margin:28px 0 0;padding:0;border-top:1px solid var(--line)}
.level{border-bottom:1px solid var(--line);padding:16px 0}
.level-head{display:flex;justify-content:space-between;align-items:baseline;gap:12px}
.level-num{font-family:var(--serif);color:var(--muted);font-size:.95rem}
.topics{list-style:none;padding:0;margin:10px 0 0;display:flex;flex-direction:column;gap:8px}
.topic{display:flex;justify-content:space-between;align-items:center;gap:10px;width:100%;text-align:left;border:1px solid var(--line);background:var(--surface);border-radius:12px;padding:12px 14px}
.topic.open{border-color:var(--accent)}
.topic.open:hover{background:var(--soft)}
.topic[disabled]{cursor:default;opacity:.62}
.topic small{display:block;color:var(--muted);font-size:.88rem}
.pill{font-size:.8rem;color:var(--muted);white-space:nowrap}
.go{color:var(--accent);font-weight:700;white-space:nowrap}

/* Exercise */
.ex-head{display:flex;justify-content:space-between;align-items:baseline;gap:10px;margin-bottom:6px}
.score{font-size:.9rem;color:var(--muted)}
.prop{font-family:var(--serif);font-size:1.45rem;line-height:1.35;margin:14px 0 6px}
.argument{font-family:var(--serif);font-size:1.25rem;line-height:1.5;margin:14px 0 4px;display:inline-block}
.argument .line{display:flex;gap:10px}
.argument .lab{width:1.2em;color:var(--muted);flex:none}
.argument .concl{border-top:2px solid var(--ink);margin-top:4px;padding-top:4px}
.key{display:flex;flex-wrap:wrap;gap:6px 16px;font-size:.92rem;color:var(--muted);margin:6px 0 0}
.key b{color:var(--ink);font-family:var(--serif)}
.step{margin-top:26px;padding-top:18px;border-top:1px solid var(--line)}
.step h3{margin-bottom:4px}
.step .hint{font-size:.92rem;color:var(--muted)}
.choices{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px;margin-top:10px}
.choice{border:1.5px solid var(--line);background:var(--surface);border-radius:10px;padding:10px 12px;text-align:left}
.choice b{font-family:var(--serif);margin-right:6px}
.choice.picked{border-color:var(--accent);background:var(--soft)}
.choice.right{border-color:var(--good);background:var(--good-tint)}
.choice.wrong{border-color:var(--bad);background:var(--bad-bg)}
.selects{display:flex;flex-wrap:wrap;gap:12px;align-items:flex-end;margin-top:10px}
.selects label{display:flex;flex-direction:column;font-size:.85rem;color:var(--muted);gap:4px}
select{font:inherit;font-size:1.05rem;padding:8px 10px;border-radius:8px;border:1.5px solid var(--line);background:var(--surface);color:var(--ink);min-width:64px}
.venn-wrap{margin:12px auto 0;max-width:340px}
.venn{width:100%;height:auto;display:block;touch-action:manipulation;user-select:none;-webkit-user-select:none}
.venn.live{cursor:pointer}
.legend{display:flex;gap:16px;justify-content:center;font-size:.85rem;color:var(--muted);margin-top:4px;flex-wrap:wrap}
.legend span{display:inline-flex;align-items:center;gap:6px}
.sw{width:18px;height:14px;border:1.5px solid var(--ink);border-radius:3px;display:inline-block}
.actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:12px}
.btn{border:0;border-radius:10px;padding:11px 18px;font-weight:700;background:var(--accent);color:var(--accent-ink)}
.btn.ghost{background:transparent;color:var(--accent);border:1.5px solid var(--accent)}
.fb{margin-top:12px;padding:12px 14px;border-radius:10px;font-size:.97rem}
.fb.good{background:var(--good-tint);color:var(--ink);border-left:4px solid var(--good)}
.fb.bad{background:var(--bad-bg);color:var(--ink);border-left:4px solid var(--bad)}
.fb strong{display:block;margin-bottom:2px}
.fb ol{margin:6px 0 0;padding-left:1.2em}
.fb li{margin:3px 0}
.answer-title{font-size:.9rem;color:var(--muted);text-align:center;margin-top:10px}
.next{margin-top:30px;display:flex;justify-content:flex-end}
.forms{overflow-x:auto;margin-top:8px}
.forms table{border-collapse:collapse;width:100%;font-size:.98rem}
.forms th{text-align:left;font-weight:700;color:var(--muted);font-size:.85rem;padding:6px 10px 6px 0;border-bottom:1.5px solid var(--ink)}
.forms td{padding:8px 10px 8px 0;border-bottom:1px solid var(--line);vertical-align:top}
.forms td b{font-family:var(--serif);font-weight:600}
.forms td small{display:block;color:var(--muted);font-size:.82rem}
.settings{display:flex;align-items:center;gap:8px;font-size:.9rem;color:var(--muted);margin-top:28px}
@media (max-width:380px){ h1{font-size:2rem} .prop{font-size:1.3rem} .argument{font-size:1.12rem} }
@media (prefers-reduced-motion:no-preference){ .fb{animation:pop .18s ease-out} @keyframes pop{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}} }

/* ===== Shared: key definitions, setting toggles, footer, credits ===== */
.defs{margin:16px 0 4px;border:1px solid var(--line);border-radius:12px;background:var(--surface)}
.defs>summary{cursor:pointer;padding:12px 14px;font-weight:700;list-style:none;display:flex;justify-content:space-between;align-items:center;gap:10px}
.defs>summary::-webkit-details-marker{display:none}
.defs>summary::after{content:'+';color:var(--accent);font-size:1.4rem;line-height:1}
.defs[open]>summary::after{content:'−'}
.defs-body{padding:0 14px 14px}
.defs h4{font-family:var(--serif);font-size:1.02rem;margin:16px 0 2px;color:var(--accent)}
.defs dl{margin:0}
.defs dt{font-weight:700;margin-top:10px}
.defs dd{margin:2px 0 0}
.defs .ex{display:block;color:var(--muted);font-size:.93rem;margin-top:3px}
.seg{display:flex;flex-wrap:wrap;align-items:center;gap:6px;margin:12px 0 0;font-size:.9rem}
.seg-label{color:var(--muted);margin-right:2px}
.seg button{border:1.5px solid var(--line);background:var(--surface);border-radius:999px;padding:5px 12px}
.seg button.on{border-color:var(--accent);background:var(--accent);color:var(--accent-ink);font-weight:700}
.foot{margin-top:22px;font-size:.92rem;color:var(--muted)}
.foot a,.credits a,.link{color:var(--accent);font-weight:700}
.credits{list-style:none;padding:0;margin:16px 0}
.credits li{border:1px solid var(--line);border-radius:12px;padding:12px 14px;margin-bottom:10px;background:var(--surface);overflow-wrap:anywhere}
.credits h3{margin-bottom:4px}
.sent{font-family:var(--serif)}
.section-title{margin-top:26px}

/* ===== Square of opposition ===== */
.square{max-width:330px;margin:12px auto 0}
.square svg{width:100%;height:auto;display:block}
.sq-rows{display:flex;flex-direction:column;gap:10px;margin-top:10px}
.sq-row{border:1px solid var(--line);border-radius:10px;padding:10px 12px;background:var(--surface)}
.sq-row .sent{font-size:1.1rem}
.tri{display:flex;gap:6px;margin-top:8px}
.tri .choice{flex:1;text-align:center;padding:8px 6px}

/* ===== Fallacies ===== */
.passage{font-family:var(--serif);font-size:1.15rem;line-height:1.55;margin:14px 0 6px;padding:12px 16px;border-left:4px solid var(--accent);background:var(--surface);border-radius:0 10px 10px 0}
.choices.one{grid-template-columns:1fr}
.fam-tag{display:inline-block;font-size:.8rem;color:var(--muted);border:1px solid var(--line);border-radius:999px;padding:2px 10px}

/* ===== Sentential logic: sentences, tables ===== */
.sentence{font-family:var(--serif);font-size:1.4rem;line-height:1.4;margin:14px 0 6px}
.mc{display:flex;flex-wrap:wrap;gap:3px;align-items:center;font-family:var(--serif);font-size:1.4rem;margin:14px 0 6px}
.mc button.tok{border:1.5px dashed var(--accent);border-radius:8px;background:var(--surface);padding:2px 9px;font-family:var(--serif);font-size:1.35rem;color:var(--ink)}
.mc button.tok.right{border-style:solid;border-color:var(--good);background:var(--good-tint)}
.mc button.tok.wrong{border-style:solid;border-color:var(--bad);background:var(--bad-bg)}
.tt-wrap{overflow-x:auto;margin-top:10px;border:1px solid var(--line);border-radius:10px;background:var(--surface)}
.tt{border-collapse:collapse;font-family:var(--serif);font-size:1.02rem;margin:0 auto}
.tt th,.tt td{text-align:center;padding:3px 2px;min-width:1.4em;border-bottom:1px solid var(--line)}
.tt thead th{padding:8px 3px;border-bottom:2px solid var(--ink);font-weight:600;white-space:nowrap}
.tt .sep{border-right:2px solid var(--ink);padding-right:6px}
.tt .main{background:var(--soft)}
.tt .atomv{color:var(--muted)}
.tt .rn{color:var(--muted);font-family:var(--sans);font-size:.8rem;padding-right:6px}
.tt button.cell,.tt .ro{width:1.9em;height:1.9em;border:1.5px solid var(--line);border-radius:6px;background:var(--paper);font-family:var(--serif);font-weight:600;font-size:1rem;padding:0;display:inline-flex;align-items:center;justify-content:center;color:var(--ink)}
.tt .ro{border-color:transparent;background:transparent}
.tt button.cell.wrong{border-color:var(--bad);background:var(--bad-bg)}
.tt button.cell.right{border-color:var(--good);background:var(--good-tint)}
.tt button.cell.sel{border-color:var(--accent);box-shadow:0 0 0 2px var(--accent)}
.tt tr.hl td{background:var(--good-tint)}
.tt tr.badrow td{background:var(--bad-bg)}
.args{font-family:var(--serif);font-size:1.2rem;margin:12px 0 4px;line-height:1.6}
.char-tables{display:flex;flex-wrap:wrap;gap:10px;margin-top:8px}
.char-tables .tt{font-size:.92rem;margin:0}

/* ===== Symbol entry ===== */
.sym-input{width:100%;font-family:var(--serif);font-size:1.2rem;padding:10px 12px;border:1.5px solid var(--line);border-radius:10px;background:var(--surface);color:var(--ink)}
.sym-input:focus{outline:3px solid var(--accent);outline-offset:1px}
.keys{display:flex;flex-wrap:wrap;gap:6px;margin-top:8px}
.keys button{min-width:2.5em;padding:6px 10px;border:1.5px solid var(--line);border-radius:8px;background:var(--surface);font-family:var(--serif);font-size:1.1rem}
.keys.rules button{font-size:.98rem}
.symkey{font-size:.95rem;color:var(--muted);margin:6px 0 0;padding-left:0;list-style:none}
.symkey li{margin:2px 0}
.symkey b{font-family:var(--serif);color:var(--ink)}
.field-label{display:block;font-size:.85rem;color:var(--muted);margin:10px 0 4px}

/* ===== Proofs (Fitch style) ===== */
.proof{font-family:var(--serif);font-size:1.08rem;margin:14px 0 6px;overflow-x:auto;padding-bottom:4px}
.pl{display:flex;align-items:stretch;min-height:2.1em;min-width:max-content}
.pl .ln{width:2em;flex:none;color:var(--muted);text-align:right;padding-right:8px;align-self:center;font-family:var(--sans);font-size:.9rem}
.pl .bar{flex:none;width:16px;border-left:2px solid var(--ink)}
.pl .bar.open{margin-top:7px}
.pl .body{flex:1;display:flex;justify-content:space-between;gap:18px;align-items:center;padding:2px 0 2px 2px}
.pl.asm .s,.pl.lastprem .s{border-bottom:2px solid var(--ink);padding-bottom:1px}
.pl .j{color:var(--muted);font-family:var(--sans);font-size:.9rem;white-space:nowrap}
.pl.ghost{opacity:.45}
.pl.ghost .s{font-style:italic;font-family:var(--sans);font-size:.9rem}
.der-list{list-style:none;padding:0;margin:8px 0 0;display:grid;grid-template-columns:repeat(auto-fill,minmax(9.5rem,1fr));gap:8px}
.der-list button{width:100%;text-align:left;border:1px solid var(--line);background:var(--surface);border-radius:10px;padding:8px 10px;font-family:var(--serif);font-size:.95rem}
.der-list button small{display:block;font-family:var(--sans);color:var(--muted);font-size:.78rem}
.der-list button.done{border-color:var(--good)}
.hint-box{margin-top:10px;padding:10px 14px;border-radius:10px;background:var(--soft);font-size:.96rem}
.choice small{display:block;color:var(--muted);font-size:.95rem;margin-top:3px}
.kbd{white-space:nowrap}

/* ===== Playful look (default; Settings → Look) ===== */
:root{ --radius:12px; --tint1:var(--surface); --tint2:var(--surface); --tint3:var(--surface); --tint4:var(--surface); --lift:none; }
:root[data-look="playful"]{
  --paper:#FFF8F2; --surface:#FFFFFF; --ink:#3A2E4F; --muted:#76688A; --line:#EEDFEA;
  --accent:#6E43E0; --accent-ink:#FFFFFF; --hatch:#8B63F0; --mark:#3A2E4F;
  --good:#1C7F5B; --good-tint:#DDF5EA; --bad:#C7364B; --bad-tint:rgba(199,54,75,.15); --bad-bg:#FDE8EB;
  --soft:#F3ECFF; --radius:18px;
  --tint1:#FFF0E6; --tint2:#F2ECFF; --tint3:#E6F7EF; --tint4:#E8F3FF;
  --lift:0 2px 0 rgba(58,46,79,.08), 0 6px 16px rgba(58,46,79,.06);
  color-scheme: light;
}
@media (prefers-color-scheme: dark){
  :root[data-look="playful"]:not([data-theme="light"]){
    --paper:#1E1A2B; --surface:#2A2440; --ink:#F4EEFF; --muted:#BDB2D3; --line:#3E3658;
    --accent:#C6ACFF; --accent-ink:#1E1A2B; --hatch:#C6ACFF; --mark:#F4EEFF;
    --good:#7BDCB5; --good-tint:#1D3B33; --bad:#FF9AA8; --bad-tint:rgba(255,154,168,.2); --bad-bg:#3F2230;
    --soft:#352D4F; --tint1:#3A2C33; --tint2:#332B4D; --tint3:#26393A; --tint4:#263447;
    --lift:0 2px 0 rgba(0,0,0,.25); color-scheme: dark;
  }
}
:root[data-look="playful"][data-theme="dark"]{
  --paper:#1E1A2B; --surface:#2A2440; --ink:#F4EEFF; --muted:#BDB2D3; --line:#3E3658;
  --accent:#C6ACFF; --accent-ink:#1E1A2B; --hatch:#C6ACFF; --mark:#F4EEFF;
  --good:#7BDCB5; --good-tint:#1D3B33; --bad:#FF9AA8; --bad-tint:rgba(255,154,168,.2); --bad-bg:#3F2230;
  --soft:#352D4F; --tint1:#3A2C33; --tint2:#332B4D; --tint3:#26393A; --tint4:#263447;
  --lift:0 2px 0 rgba(0,0,0,.25); color-scheme: dark;
}
[data-look="playful"] .topic,[data-look="playful"] .defs,[data-look="playful"] .sq-row,[data-look="playful"] .credits li,[data-look="playful"] .tt-wrap{border-radius:var(--radius);box-shadow:var(--lift)}
[data-look="playful"] .topic.open{border-color:var(--line)}
[data-look="playful"] .level:nth-child(4n+1) .topic.open{background:var(--tint1)}
[data-look="playful"] .level:nth-child(4n+2) .topic.open{background:var(--tint2)}
[data-look="playful"] .level:nth-child(4n+3) .topic.open{background:var(--tint3)}
[data-look="playful"] .level:nth-child(4n+4) .topic.open{background:var(--tint4)}
[data-look="playful"] .topic.open:hover{filter:brightness(.98)}
[data-look="playful"] .level{border-bottom:0;padding:14px 0 6px}
[data-look="playful"] .levels{border-top:0}
[data-look="playful"] .level-num{background:var(--soft);color:var(--accent);font-family:var(--sans);font-weight:700;font-size:.8rem;padding:3px 10px;border-radius:999px}
[data-look="playful"] .go{background:var(--surface);padding:5px 12px;border-radius:999px;box-shadow:var(--lift)}
[data-look="playful"] .btn,[data-look="playful"] .choice,[data-look="playful"] select,[data-look="playful"] .sym-input,[data-look="playful"] .keys button,[data-look="playful"] .der-list button{border-radius:14px}
[data-look="playful"] .btn{box-shadow:0 3px 0 rgba(58,46,79,.18)}
[data-look="playful"] .btn:active{transform:translateY(2px);box-shadow:none}
[data-look="playful"] .fb{border-radius:14px;border-left-width:0;border:1.5px solid transparent}
[data-look="playful"] .fb.good{border-color:var(--good)}
[data-look="playful"] .fb.bad{border-color:var(--bad)}
[data-look="playful"] .passage{border-radius:var(--radius);border-left:0;background:var(--tint2);box-shadow:var(--lift)}
[data-look="playful"] .hero h1{color:var(--accent)}

/* ===== Celebrations ===== */
.fb.good>strong:first-child::before{content:'✓';display:inline-flex;align-items:center;justify-content:center;width:1.35em;height:1.35em;margin-right:.4em;border-radius:50%;background:var(--good);color:var(--surface);font-size:.85em;vertical-align:.08em}
.confetti{position:relative;height:0;width:0;margin:0 auto;pointer-events:none}
.confetti span{position:absolute;left:0;top:0;width:9px;height:13px;border-radius:3px;background:var(--c);opacity:0}
#toast{position:fixed;left:50%;bottom:calc(20px + env(safe-area-inset-bottom,0px));transform:translate(-50%,30px);opacity:0;pointer-events:none;
  background:var(--ink);color:var(--paper);font-weight:700;padding:12px 20px;border-radius:999px;box-shadow:0 8px 24px rgba(0,0,0,.18);z-index:10;transition:opacity .25s,transform .25s}
#toast.show{opacity:1;transform:translate(-50%,0)}
#toast .confetti{position:absolute;left:50%;top:0}
@media (prefers-reduced-motion:no-preference){
  .fb.good>strong:first-child::before{animation:checkpop .45s cubic-bezier(.3,1.7,.5,1)}
  @keyframes checkpop{from{transform:scale(0)}to{transform:scale(1)}}
  .confetti span{animation:burst 1.1s cubic-bezier(.15,.7,.3,1) var(--d) forwards}
  @keyframes burst{0%{opacity:1;transform:translate(0,0) rotate(0)}70%{opacity:1}100%{opacity:0;transform:translate(var(--x),calc(var(--y) + 70px)) rotate(var(--r))}}
}
@media (prefers-reduced-motion:reduce){ .confetti{display:none} #toast{transition:none} }

/* ===== Roomier tap targets on touch screens ===== */
@media (pointer:coarse){
  .tt button.cell,.tt .ro{width:2.35em;height:2.35em}
  .keys button{min-height:44px;min-width:44px}
  .seg button{min-height:38px;padding:6px 14px}
  .mc button.tok{min-height:44px;min-width:40px}
  .back{padding:10px 0}
  .choice{min-height:46px}
}
.hero-icon{width:84px;height:84px;flex:none;border-radius:22px;box-shadow:var(--lift)}