:root{
  --bg:#f5f6fb; --panel:#ffffff; --panel2:#eef1fa; --ink:#141834; --muted:#5d6491; --line:#dde2f2;
  --plotbg:#fbfcff; --grid:rgba(30,40,120,.055); --gridmajor:rgba(30,40,120,.13); --axis:#3a4270;
  --accent:#3b5bdb; --curve:#0a84c6; --curve2:#0ca678; --focus:#d6336c; --dir:#d08700; --vert:#2f9e44; --asy:#7048e8; --pt:#141834;
  --ok:#2b8a3e; --bad:#e03131; --fill:#3b5bdb;
  --shadow:0 1px 2px rgba(20,24,52,.06),0 8px 28px rgba(20,24,52,.07);
  --r:16px;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){
  :root:not([data-theme="light"]){
    --bg:#070b17; --panel:#0f1528; --panel2:#151d36; --ink:#e9edff; --muted:#8e98c6; --line:#222c50;
    --plotbg:#0a1022; --grid:rgba(140,160,255,.06); --gridmajor:rgba(140,160,255,.15); --axis:#9aa6d8;
    --accent:#7c9cff; --curve:#4fe3ff; --curve2:#5cf2b0; --focus:#ff5fa2; --dir:#ffc24b; --vert:#8dff6a; --asy:#b18cff; --pt:#ffffff;
    --ok:#3ddc97; --bad:#ff6b6b; --fill:#7c9cff;
    --shadow:0 1px 2px rgba(0,0,0,.4),0 10px 30px rgba(0,0,0,.35);
    color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --bg:#070b17; --panel:#0f1528; --panel2:#151d36; --ink:#e9edff; --muted:#8e98c6; --line:#222c50;
  --plotbg:#0a1022; --grid:rgba(140,160,255,.06); --gridmajor:rgba(140,160,255,.15); --axis:#9aa6d8;
  --accent:#7c9cff; --curve:#4fe3ff; --curve2:#5cf2b0; --focus:#ff5fa2; --dir:#ffc24b; --vert:#8dff6a; --asy:#b18cff; --pt:#ffffff;
  --ok:#3ddc97; --bad:#ff6b6b; --fill:#7c9cff;
  --shadow:0 1px 2px rgba(0,0,0,.4),0 10px 30px rgba(0,0,0,.35);
  color-scheme:dark;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:15px/1.55 Inter,system-ui,-apple-system,Segoe UI,sans-serif;overflow-x:hidden}
h1,h2,h3,h4{font-family:"Space Grotesk",Inter,sans-serif;letter-spacing:-.01em;margin:0}
button{font:inherit;color:inherit}
a{color:var(--accent)}
.muted{color:var(--muted)}
.katex{font-size:1.06em}
.katex-display{margin:.3em 0}

/* ---------- hero ---------- */
.hero{position:relative;overflow:hidden;border-bottom:1px solid var(--line);background:radial-gradient(1200px 400px at 75% 20%,color-mix(in srgb,var(--accent) 16%,transparent),transparent 70%),var(--bg)}
#hero-cv{position:absolute;inset:0;width:100%;height:100%}
.hero-in{position:relative;max-width:1280px;margin:0 auto;padding:28px 24px 34px;pointer-events:none}
.hero-in *{pointer-events:auto}
.hero-top{display:flex;justify-content:space-between;align-items:center;gap:12px}
.kicker{font:600 12px/1 "JetBrains Mono",monospace;text-transform:uppercase;letter-spacing:.12em;color:var(--muted)}
.hero h1{font-size:clamp(44px,9vw,92px);line-height:.95;margin:14px 0 10px;font-weight:700}
.hero h1 .dot{color:var(--focus)}
.hero .sub{max-width:560px;color:var(--muted);margin:0;font-size:15.5px}
.hero .sub b{color:var(--curve);font-family:"JetBrains Mono",monospace;white-space:nowrap}
.iconbtn{width:38px;height:38px;border-radius:12px;border:1px solid var(--line);background:var(--panel);cursor:pointer;font-size:18px;box-shadow:var(--shadow)}

/* ---------- tabs ---------- */
.tabs{position:sticky;top:0;z-index:20;background:color-mix(in srgb,var(--bg) 86%,transparent);backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);border-bottom:1px solid var(--line)}
.tabs-in{max-width:1280px;margin:0 auto;display:flex;gap:6px;padding:10px 16px;overflow-x:auto;scrollbar-width:none}
.tabs-in::-webkit-scrollbar{display:none}
.tabs a{flex:none;text-decoration:none;color:var(--muted);font-weight:600;font-size:14px;padding:8px 13px;border-radius:999px;border:1px solid transparent;white-space:nowrap;transition:.15s}
.tabs a:hover{color:var(--ink);background:var(--panel2)}
.tabs a.on{color:var(--ink);background:var(--panel);border-color:var(--line);box-shadow:var(--shadow)}
.tabs a.star{color:var(--focus)}
.tabs a.star.on{background:color-mix(in srgb,var(--focus) 14%,var(--panel));border-color:color-mix(in srgb,var(--focus) 40%,transparent);color:var(--focus)}

/* ---------- sezioni ---------- */
main{max-width:1280px;margin:0 auto;padding:22px 16px 40px}
.sec{display:none}
.sec.on{display:block;animation:secin .35s ease}
@keyframes secin{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}
.sec-head{margin:4px 2px 16px;display:flex;flex-wrap:wrap;align-items:flex-end;justify-content:space-between;gap:10px}
.sec-head h2{font-size:clamp(26px,4vw,34px)}
.sec-head p{margin:4px 0 0;color:var(--muted);max-width:720px}
.lab{display:grid;grid-template-columns:minmax(0,1.65fr) minmax(310px,1fr);gap:16px;align-items:start}
@media (max-width:920px){.lab{grid-template-columns:minmax(0,1fr)}}
.stage{position:relative;background:var(--panel);border:1px solid var(--line);border-radius:var(--r);box-shadow:var(--shadow);overflow:hidden}
@media (min-width:921px){.stage.sticky{position:sticky;top:64px}}
.plot{position:relative;height:min(600px,72vh);min-height:300px;touch-action:none;user-select:none;-webkit-user-select:none}
.plot canvas{display:block}
@media (max-width:920px){.plot{height:56vh;min-height:300px}}
.ptools{position:absolute;right:10px;top:10px;display:flex;flex-direction:column;gap:6px;z-index:2}
.ptools button{width:34px;height:34px;border-radius:10px;border:1px solid var(--line);background:color-mix(in srgb,var(--panel) 90%,transparent);cursor:pointer;font-size:17px;font-weight:600;box-shadow:var(--shadow)}
.ptools button:hover{border-color:var(--accent)}
.hint{position:absolute;left:12px;bottom:10px;font-size:12px;color:var(--muted);background:color-mix(in srgb,var(--panel) 85%,transparent);padding:4px 9px;border-radius:8px;pointer-events:none;border:1px solid var(--line)}
.eqtag{position:absolute;left:12px;top:12px;z-index:2;background:color-mix(in srgb,var(--panel) 88%,transparent);border:1px solid var(--line);border-radius:12px;padding:6px 12px;box-shadow:var(--shadow);max-width:calc(100% - 70px);overflow-x:auto;pointer-events:none}

.panel{display:flex;flex-direction:column;gap:12px;min-width:0}
.box{background:var(--panel);border:1px solid var(--line);border-radius:var(--r);padding:14px 16px;box-shadow:var(--shadow);min-width:0}
.box h3{font-size:15px;margin-bottom:8px;display:flex;align-items:center;gap:8px}
.box h3 .tag{font:600 11px "JetBrains Mono",monospace;color:var(--muted);text-transform:uppercase;letter-spacing:.08em}
.card{background:var(--panel2);border-radius:12px;padding:10px 12px;margin-top:8px;overflow-x:auto;overflow-y:hidden}
.card h4{font:600 12px Inter,sans-serif;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);margin-bottom:2px}
.card.ok{background:color-mix(in srgb,var(--ok) 13%,var(--panel2))}
.card.bad{background:color-mix(in srgb,var(--bad) 13%,var(--panel2))}
.dm{overflow-x:auto;overflow-y:hidden;padding:2px 0}
.mrow{display:flex;justify-content:space-between;align-items:baseline;gap:10px;padding:5px 0;border-bottom:1px dashed var(--line)}
.mrow:last-child{border-bottom:0}
.mrow>span{color:var(--muted);font-size:13px;flex:none}
.mrow .mv{overflow-x:auto;overflow-y:hidden;text-align:right;padding:3px 0}
.note{font-size:13.5px;color:var(--muted);margin:6px 0 0}
.pill{display:inline-block;font:700 11.5px Inter,sans-serif;padding:3px 9px;border-radius:999px;background:var(--panel2);border:1px solid var(--line)}
.pill.ok{color:var(--ok);border-color:color-mix(in srgb,var(--ok) 50%,transparent)}
.pill.bad{color:var(--bad);border-color:color-mix(in srgb,var(--bad) 50%,transparent)}
.legend{display:flex;flex-wrap:wrap;gap:6px 12px;font-size:12.5px;color:var(--muted);margin-top:6px}
.legend i{display:inline-block;width:14px;height:3px;border-radius:2px;vertical-align:middle;margin-right:5px;background:var(--c)}

/* controlli */
.ctrls{display:flex;flex-direction:column;gap:10px}
.sl{display:grid;grid-template-columns:46px 1fr 54px;align-items:center;gap:10px}
.sl-l{font:600 14px "JetBrains Mono",monospace;color:var(--ink)}
.sl output{font:600 13px "JetBrains Mono",monospace;text-align:right;color:var(--accent)}
input[type=range]{-webkit-appearance:none;appearance:none;width:100%;height:28px;background:transparent;margin:0}
input[type=range]::-webkit-slider-runnable-track{height:6px;border-radius:6px;background:var(--panel2);border:1px solid var(--line)}
input[type=range]::-moz-range-track{height:6px;border-radius:6px;background:var(--panel2);border:1px solid var(--line)}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:20px;height:20px;border-radius:50%;background:var(--accent);margin-top:-8px;border:3px solid var(--panel);box-shadow:0 0 0 1px var(--accent),0 2px 6px rgba(0,0,0,.25)}
input[type=range]::-moz-range-thumb{width:16px;height:16px;border-radius:50%;background:var(--accent);border:3px solid var(--panel)}
.chks{display:flex;flex-wrap:wrap;gap:6px}
.chk{display:inline-flex;align-items:center;gap:7px;font-size:13.5px;cursor:pointer;padding:6px 10px 6px 8px;border-radius:10px;background:var(--panel2);border:1px solid var(--line);user-select:none}
.chk input{position:absolute;opacity:0;pointer-events:none}
.chk .box{all:unset;width:16px;height:16px;border-radius:5px;border:2px solid var(--c,var(--accent));display:inline-block;position:relative;flex:none}
.chk input:checked+.box{background:var(--c,var(--accent))}
.chk input:checked+.box::after{content:"";position:absolute;left:4px;top:0;width:4px;height:9px;border:solid var(--panel);border-width:0 2px 2px 0;transform:rotate(45deg)}
.chk input:focus-visible+.box{outline:2px solid var(--accent);outline-offset:2px}
.segm{display:flex;background:var(--panel2);border:1px solid var(--line);border-radius:12px;padding:3px;gap:3px;flex-wrap:wrap}
.segm button{flex:1 1 auto;border:0;background:transparent;border-radius:9px;padding:7px 10px;font-size:13.5px;font-weight:600;color:var(--muted);cursor:pointer}
.segm button[aria-checked="true"]{background:var(--panel);color:var(--ink);box-shadow:var(--shadow)}
.btn{border:1px solid var(--line);background:var(--panel2);border-radius:11px;padding:8px 14px;font-weight:600;font-size:14px;cursor:pointer;display:inline-flex;align-items:center;gap:7px;transition:.12s}
.btn:hover{border-color:var(--accent)}
.btn:active{transform:translateY(1px)}
.btn.pri{background:var(--accent);border-color:var(--accent);color:#fff}
.btn.pri:hover{filter:brightness(1.08)}
.btn.ghost{background:transparent}
.btn:disabled{opacity:.45;cursor:default}
.row{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
details.formule{margin-top:4px}
details.formule summary{cursor:pointer;font-weight:600;font-size:14px;color:var(--accent);list-style:none}
details.formule summary::before{content:"▸ ";}
details.formule[open] summary::before{content:"▾ ";}

/* ---------- esercizi ---------- */
.exgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:10px;margin-bottom:16px}
.excard{text-align:left;border:1px solid var(--line);background:var(--panel);border-radius:14px;padding:11px 12px;cursor:pointer;box-shadow:var(--shadow);position:relative;overflow:hidden;transition:.15s;min-width:0}
.excard:hover{transform:translateY(-2px);border-color:var(--c)}
.excard.on{border-color:var(--c);background:color-mix(in srgb,var(--c) 10%,var(--panel))}
.excard .n{font:700 22px "Space Grotesk",sans-serif}
.excard .t{display:inline-block;font:700 10.5px Inter,sans-serif;text-transform:uppercase;letter-spacing:.07em;color:var(--c);margin-left:6px}
.excard .q{font-size:12.5px;color:var(--muted);margin-top:4px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.excard .bar{position:absolute;left:0;bottom:0;height:3px;background:var(--c);transition:width .4s}
.excard.sim{border-style:dashed}
.exbar{display:flex;flex-wrap:wrap;gap:8px;align-items:center;justify-content:space-between;padding:10px 12px;border-top:1px solid var(--line);background:var(--panel)}
.exbar .row{gap:6px}
.stepcount{font:600 13px "JetBrains Mono",monospace;color:var(--muted);min-width:68px;text-align:center}
.extext{font-size:15px}
.extext .katex-display{font-size:1.05em}
.steps{list-style:none;margin:10px 0 0;padding:0;position:relative}
.steps li{position:relative;padding-left:38px;margin-bottom:6px}
.steps li::before{content:"";position:absolute;left:13px;top:30px;bottom:-8px;width:2px;background:var(--line)}
.steps li:last-child::before{display:none}
.st-h{all:unset;cursor:pointer;display:flex;align-items:center;gap:10px;font-weight:600;font-size:14.5px;padding:4px 0;width:100%;box-sizing:border-box}
.st-n{position:absolute;left:0;top:2px;width:28px;height:28px;border-radius:50%;display:grid;place-items:center;font:700 12.5px "JetBrains Mono",monospace;background:var(--panel2);border:2px solid var(--line);color:var(--muted)}
.steps li.done .st-n{background:var(--ok);border-color:var(--ok);color:var(--panel)}
.steps li.cur .st-n{background:var(--accent);border-color:var(--accent);color:#fff;box-shadow:0 0 0 5px color-mix(in srgb,var(--accent) 22%,transparent)}
.steps li.todo .st-h{color:var(--muted)}
.st-b{display:none;padding:4px 0 10px;font-size:14.5px}
.steps li.cur .st-b{display:block;animation:secin .3s ease}
.steps li.done.peek .st-b{display:block;opacity:.85}
.st-b p{margin:.35em 0}
.st-b .katex-display{overflow-x:auto;overflow-y:hidden}
.quiz{background:var(--panel2);border:1px dashed color-mix(in srgb,var(--accent) 45%,var(--line));border-radius:12px;padding:10px 12px;margin-top:6px}
.quiz .qrow{display:flex;align-items:center;gap:8px;margin:6px 0;flex-wrap:wrap}
.quiz .qrow label{min-width:64px;font-size:14px}
.quiz input{width:120px;padding:7px 10px;border-radius:9px;border:1.5px solid var(--line);background:var(--panel);color:var(--ink);font:500 14px "JetBrains Mono",monospace}
.quiz input.ok{border-color:var(--ok);background:color-mix(in srgb,var(--ok) 10%,var(--panel))}
.quiz input.bad{border-color:var(--bad);background:color-mix(in srgb,var(--bad) 10%,var(--panel));animation:shake .3s}
@keyframes shake{25%{transform:translateX(-4px)}75%{transform:translateX(4px)}}
.quiz .qmsg{font-size:13px;margin-top:4px;min-height:1.2em}
.switch{display:inline-flex;align-items:center;gap:8px;cursor:pointer;font-weight:600;font-size:13.5px;user-select:none}
.switch input{position:absolute;opacity:0}
.switch .tr{width:38px;height:22px;border-radius:99px;background:var(--panel2);border:1px solid var(--line);position:relative;transition:.15s}
.switch .tr::after{content:"";position:absolute;left:2px;top:2px;width:16px;height:16px;border-radius:50%;background:var(--muted);transition:.15s}
.switch input:checked+.tr{background:var(--accent);border-color:var(--accent)}
.switch input:checked+.tr::after{left:18px;background:#fff}
.switch input:focus-visible+.tr{outline:2px solid var(--accent);outline-offset:2px}
.summary{margin-top:10px}
.summary table{width:100%;border-collapse:collapse;font-size:14px}
.summary td{padding:5px 4px;border-bottom:1px dashed var(--line);vertical-align:top}
.summary td:first-child{color:var(--muted);white-space:nowrap;padding-right:10px}
.conf{position:absolute;top:55%;width:8px;height:12px;border-radius:2px;z-index:5;pointer-events:none;animation:conf 1.4s cubic-bezier(.2,.6,.3,1) forwards}
@keyframes conf{0%{transform:translate(0,0) rotate(0);opacity:1}100%{transform:translate(var(--dx),calc(var(--dy) + 420px)) rotate(var(--r));opacity:0}}

/* ---------- cono 3D ---------- */
.cone3d{position:relative;height:min(560px,64vh);min-height:300px;touch-action:none;cursor:grab}
.cone3d canvas{display:block;width:100%;height:100%}
.duo{display:grid;grid-template-columns:1fr 1fr;gap:0}
.duo>.cone3d{border-right:1px solid var(--line)}
@media (max-width:700px){.duo{grid-template-columns:1fr}.duo>.cone3d{border-right:0;border-bottom:1px solid var(--line);height:48vh}.duo .plot{height:40vh}}
.duo .plot{height:min(560px,64vh)}
.ctype{font:700 24px "Space Grotesk",sans-serif}

/* ---------- formulario ---------- */
.fgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(320px,1fr));gap:14px}
.fgrid .box h3{font-size:18px}
.fgrid .box h3 .sw{width:12px;height:12px;border-radius:4px;background:var(--c)}
.ftab{width:100%;border-collapse:collapse;font-size:14px}
.ftab td{padding:6px 4px;border-bottom:1px dashed var(--line);vertical-align:middle}
.ftab td:first-child{color:var(--muted);white-space:nowrap;padding-right:10px;font-size:13px}
.ftab td:last-child{overflow-x:auto;max-width:0;width:100%}
.ftab .katex-display{margin:0;text-align:left}

.foot{max-width:1280px;margin:0 auto;padding:20px 20px 40px;color:var(--muted);font-size:13px;border-top:1px solid var(--line)}
.foot p{margin:.4em 0}
@media (max-width:600px){
  main{padding:14px 12px 30px}
  .hero-in{padding:20px 16px 26px}
  .box{padding:12px 13px}
  .sl{grid-template-columns:38px 1fr 48px}
}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}
@media (max-width:920px){
  #esercizi .lab{display:flex;flex-direction:column}
  #esercizi .panel{display:contents}
  #esercizi .panel>.box:first-child{order:-1}
  .exgrid{grid-template-columns:repeat(auto-fill,minmax(130px,1fr))}
}