:root{
  --bg:#FFFFFF; --ink:#0B1524; --mute:rgba(11,21,36,.62);
  --blue:#007AFF; --blue-l:#5AC8FA; --blue-d:#0051C7;
  --sage:#0062CC; --pine:#003D99; --gold:#8A5A00;
  --rust:#D93025; --green:#15773F;
  --glass:rgba(255,255,255,.72); --edge:rgba(0,80,180,.13);
  --r:24px;
  --sans:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
  --serif:'Fraunces',Georgia,serif;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--ink);font-family:var(--sans);font-weight:400;-webkit-font-smoothing:antialiased}
body{min-height:100dvh;background:
  radial-gradient(1200px 600px at 10% -10%, rgba(90,200,250,.18), transparent 60%),
  radial-gradient(900px 500px at 100% 0%, rgba(0,122,255,.10), transparent 55%),
  var(--bg)}
h1,h2,h3{font-family:var(--serif);font-weight:600;letter-spacing:-.02em;margin:0}
button,input,select,textarea{font:inherit}
button{cursor:pointer}
a{color:var(--sage);text-decoration:none}
:focus-visible{outline:2px solid var(--blue);outline-offset:2px;border-radius:4px}
.skip-link{position:absolute;left:-999px;top:0;background:var(--blue);color:#fff;padding:8px 12px;z-index:100}
.skip-link:focus{left:8px;top:8px}

.shell{max-width:1100px;margin:0 auto;padding:24px 20px 96px}
.nav{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:28px;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:12px}
.logo{width:40px;height:40px;border-radius:12px;background:linear-gradient(135deg,var(--blue-l),var(--blue) 45%,var(--blue-d));display:grid;place-items:center;color:#fff;font-weight:600;box-shadow:0 8px 24px rgba(0,122,255,.25)}
.brand-text{display:flex;flex-direction:column;line-height:1.15}
.brand-text strong{font-size:15px;font-weight:600}
.brand-text span{font-size:11px;color:var(--mute);letter-spacing:.08em;text-transform:uppercase}
.nav-links{display:flex;flex-wrap:wrap;gap:8px;align-items:center}

.glass{background:var(--glass);backdrop-filter:blur(30px) saturate(165%);-webkit-backdrop-filter:blur(30px) saturate(165%);border:1px solid var(--edge);border-radius:var(--r);box-shadow:0 10px 40px rgba(0,81,199,.06)}
.hero{padding:36px 32px;margin-bottom:20px}
.hero h1{font-size:clamp(1.9rem,4.8vw,3.1rem);line-height:1.08;margin-bottom:12px}
.hero h1 em{font-style:italic;background:linear-gradient(120deg,var(--blue-l),var(--blue),var(--blue-d));-webkit-background-clip:text;background-clip:text;color:transparent}
.hero p,.muted{color:var(--mute);line-height:1.55}
.hero p{font-size:1.05rem;max-width:48ch;margin:0 0 20px}

.chips{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:20px}
.chip{padding:8px 14px;border-radius:999px;background:rgba(0,122,255,.06);border:1px solid var(--edge);font-size:13px}
.chip b{color:var(--sage);font-weight:600}

.row{display:flex;flex-wrap:wrap;gap:10px;align-items:center}
.btn{appearance:none;border:0;border-radius:999px;padding:11px 18px;font-weight:500;transition:transform .2s ease-out,box-shadow .2s ease-out,background .2s ease-out}
.btn:active{transform:scale(.98)}
.btn-primary{background:linear-gradient(135deg,var(--blue),var(--blue-d));color:#fff;box-shadow:0 8px 22px rgba(0,122,255,.28)}
.btn-ghost{background:rgba(255,255,255,.85);border:1px solid var(--edge);color:var(--ink)}
.btn-danger{background:rgba(217,48,37,.08);color:var(--rust);border:1px solid rgba(217,48,37,.2)}
.btn:disabled{opacity:.5;cursor:not-allowed}
.btn-sm{padding:7px 12px;font-size:13px}

.grid{display:grid;gap:14px}
@media(min-width:860px){.grid-2{grid-template-columns:1.35fr .9fr}.grid-3{grid-template-columns:repeat(3,1fr)}.grid-4{grid-template-columns:repeat(4,1fr)}}
.card{padding:22px}
.card h2{font-size:1.3rem;margin-bottom:8px}
.card h3{font-size:1.05rem;margin-bottom:6px}

.stat{display:flex;flex-direction:column;gap:2px}
.stat .label{font-size:11px;color:var(--mute);text-transform:uppercase;letter-spacing:.06em}
.stat .value{font-family:var(--serif);font-size:1.7rem;font-weight:600}

.form{display:flex;flex-direction:column;gap:10px;max-width:380px}
.form label{font-size:13px;color:var(--mute);font-weight:500}
.form input,.form select,textarea.input,input.input{
  border:1px solid var(--edge);border-radius:14px;padding:12px 14px;background:#fff;width:100%
}
.form input:focus,.input:focus{border-color:var(--blue);box-shadow:0 0 0 3px rgba(0,122,255,.15);outline:0}
.err{color:var(--rust);font-size:13px;margin-top:6px}
.ok{color:var(--green)}

.phase-bar{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:12px}
.phase{padding:6px 12px;border-radius:999px;font-size:12px;border:1px solid var(--edge);color:var(--mute);text-transform:capitalize}
.phase.active{background:rgba(0,122,255,.1);color:var(--sage);border-color:rgba(0,122,255,.25);font-weight:500}

.problem{padding:26px}
.problem .skill{font-size:12px;color:var(--sage);font-weight:500;margin-bottom:8px;text-transform:uppercase;letter-spacing:.05em}
.problem h2{font-size:1.35rem;margin-bottom:12px}
.problem .body{line-height:1.65;font-size:1.05rem;margin-bottom:18px;overflow-x:auto}
.choices{display:grid;gap:10px;margin-bottom:14px}
.choice{text-align:left;padding:14px 16px;border-radius:16px;border:1px solid var(--edge);background:#fff;transition:border-color .2s,background .2s}
.choice:hover,.choice.selected{border-color:var(--blue);background:rgba(0,122,255,.04)}
.answer-row{display:flex;gap:10px;flex-wrap:wrap}
.answer-row input{flex:1;min-width:180px}

.feedback{margin-top:14px;padding:16px 18px;border-radius:16px;border:1px solid var(--edge);background:rgba(255,255,255,.92);line-height:1.55}
.feedback.ok{border-color:rgba(21,119,63,.25);background:rgba(21,119,63,.06)}
.feedback.bad{border-color:rgba(217,48,37,.18);background:rgba(217,48,37,.04)}
.ladder{display:flex;gap:6px;margin:10px 0 0;flex-wrap:wrap}
.ladder span{font-size:11px;padding:4px 8px;border-radius:999px;border:1px solid var(--edge);color:var(--mute)}
.ladder span.on{background:rgba(0,122,255,.1);color:var(--sage);border-color:rgba(0,122,255,.25)}

.bar{height:8px;border-radius:999px;background:rgba(0,80,180,.08);overflow:hidden;flex:1}
.bar>i{display:block;height:100%;background:linear-gradient(90deg,var(--blue-l),var(--blue));border-radius:999px;transition:width .35s ease-out}
.progress-ring{display:flex;align-items:center;gap:14px}

table{width:100%;border-collapse:collapse;font-size:14px}
th,td{text-align:left;padding:11px 8px;border-bottom:1px solid var(--edge);vertical-align:middle}
th{font-size:11px;text-transform:uppercase;letter-spacing:.06em;color:var(--mute);font-weight:500}
.flag{display:inline-block;padding:4px 10px;border-radius:999px;font-size:12px;font-weight:500;text-transform:capitalize}
.flag.on_track{background:rgba(21,119,63,.1);color:var(--green)}
.flag.slipping{background:rgba(138,90,0,.1);color:var(--gold)}
.flag.stalled{background:rgba(217,48,37,.08);color:var(--rust)}
.flag.disengaged{background:rgba(11,21,36,.06);color:var(--mute)}
.headline-alert{padding:14px 18px;border-radius:16px;margin-bottom:14px;background:rgba(217,48,37,.06);border:1px solid rgba(217,48,37,.18)}
.headline-ok{padding:14px 18px;border-radius:16px;margin-bottom:14px;background:rgba(0,122,255,.06);border:1px solid var(--edge)}

.skill-map{display:grid;grid-template-columns:repeat(auto-fill,minmax(140px,1fr));gap:10px}
.skill-tile{padding:12px;border-radius:14px;border:1px solid var(--edge);font-size:12px;min-height:76px}
.skill-tile.mastered{background:rgba(21,119,63,.08);border-color:rgba(21,119,63,.2)}
.skill-tile.in_progress{background:rgba(0,122,255,.06)}
.skill-tile.gap{background:rgba(217,48,37,.06)}
.skill-tile.not_started{opacity:.75}
.skill-tile .p{font-family:var(--serif);font-size:1.1rem;font-weight:600;margin-top:6px}

.timer{font-variant-numeric:tabular-nums;font-weight:500;color:var(--sage)}
.timer.warn{color:var(--gold)}.timer.over{color:var(--rust)}
.tabs{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:14px}
.tab{padding:8px 14px;border-radius:999px;border:1px solid var(--edge);background:#fff;font-size:13px;color:var(--mute)}
.tab.active{background:rgba(0,122,255,.1);color:var(--sage);border-color:rgba(0,122,255,.25);font-weight:500}
.week-rail{display:flex;gap:6px;overflow-x:auto;padding-bottom:6px;margin:10px 0 16px}
.week-dot{min-width:64px;text-align:center;padding:10px 8px;border-radius:14px;border:1px solid var(--edge);font-size:12px}
.week-dot b{display:block;font-family:var(--serif);font-size:1.1rem}
.week-dot.now{border-color:var(--blue);background:rgba(0,122,255,.06)}
.week-dot.done{background:rgba(21,119,63,.08)}
.list-plain{list-style:none;padding:0;margin:0}
.list-plain li{padding:10px 0;border-bottom:1px solid var(--edge);font-size:14px}
.meta-line{font-size:12px;color:var(--mute)}
.toast{position:fixed;bottom:20px;right:20px;background:var(--ink);color:#fff;padding:12px 16px;border-radius:12px;font-size:14px;z-index:50;max-width:320px;box-shadow:0 10px 30px rgba(0,0,0,.2)}
.empty{padding:28px;text-align:center;color:var(--mute)}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);border:0}

@media (max-width:480px){
  .shell{padding:14px 12px 72px}
  .hero{padding:22px 16px}
  .problem{padding:16px}
}
@media (prefers-reduced-motion:reduce){
  *,*::before,*::after{animation:none!important;transition:none!important}
}