/* ============================================================
   Squared — a math practice site
   Design tokens
   ============================================================ */
:root {
  --paper:      #FBFCFE;
  --paper-2:    #FFFFFF;
  --grid:       #E4EAF4;   /* faint quadrille lines */
  --grid-bold:  #D3DCEC;
  --ink:        #1B2233;   /* near-navy text */
  --ink-soft:   #5A6478;
  --ink-faint:  #97A0B3;
  --primary:    #3A47D6;   /* chalk-ink blue-violet */
  --primary-d:  #2A34A8;
  --primary-w:  #EDEEFC;   /* wash */
  --ok:         #17A673;
  --ok-w:       #E4F5EE;
  --no:         #E5484D;
  --no-w:       #FCEAEA;
  --amber:      #E8912B;

  --line:       #E4EAF4;
  --shadow:     0 1px 2px rgba(27,34,51,.05), 0 8px 24px rgba(27,34,51,.06);
  --radius:     14px;

  --sans: "Space Grotesk", ui-sans-serif, system-ui, -apple-system, sans-serif;
  --serif: "Source Serif 4", Georgia, "Times New Roman", serif;
  --mono: "Space Mono", ui-monospace, "SF Mono", Menlo, monospace;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: var(--sans);
  color: var(--ink);
  /* signature: quadrille graph paper */
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 26px 26px;
  background-position: -1px -1px;
  line-height: 1.5;
  min-height: 100vh;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap { max-width: 1040px; margin: 0 auto; padding: 0 20px; }

/* ---------- Header ---------- */
.site-head {
  border-bottom: 1px solid var(--line);
  background: rgba(251,252,254,.86);
  backdrop-filter: blur(6px);
  position: sticky; top: 0; z-index: 20;
}
.site-head .wrap {
  display: flex; align-items: center; gap: 22px;
  height: 64px;
}
.brand {
  display: flex; align-items: center; gap: 10px;
  font-weight: 700; font-size: 20px; letter-spacing: -.02em;
  color: var(--ink); text-decoration: none;
}
.brand:hover { text-decoration: none; }
.brand .mark {
  width: 30px; height: 30px; border-radius: 8px;
  background: var(--ink); color: #fff;
  display: grid; place-items: center;
  font-family: var(--serif); font-style: italic; font-size: 19px;
  box-shadow: inset 0 0 0 1px rgba(255,255,255,.08);
}
.nav { display: flex; gap: 4px; margin-left: auto; align-items: center; }
.nav a {
  color: var(--ink-soft); font-weight: 500; font-size: 15px;
  padding: 7px 12px; border-radius: 8px;
}
.nav a:hover { background: var(--primary-w); color: var(--primary); text-decoration: none; }
.nav a.active { color: var(--primary); background: var(--primary-w); }
.nav a.btn { background: var(--ink); color: #fff; }
.nav a.btn:hover { background: var(--primary); }

/* ---------- Hero ---------- */
.hero { padding: 56px 0 34px; }
.hero .eyebrow {
  font-family: var(--mono); font-size: 12px; letter-spacing: .12em;
  text-transform: uppercase; color: var(--primary);
  margin: 0 0 14px;
}
.hero h1 {
  font-size: clamp(34px, 5.4vw, 52px);
  line-height: 1.04; letter-spacing: -.03em; font-weight: 700;
  margin: 0 0 16px; max-width: 15ch;
}
.hero p.lede {
  font-size: 18px; color: var(--ink-soft); max-width: 52ch; margin: 0 0 26px;
}
.hero-grid {
  display: grid; grid-template-columns: 1fr minmax(280px, 380px);
  gap: 34px; align-items: center;
}
.hero-card {
  background: var(--paper-2); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 24px 24px 22px; position: relative;
}
.hero-card::before { /* notebook margin rule */
  content: ""; position: absolute; left: 46px; top: 14px; bottom: 14px;
  width: 1px; background: var(--no-w);
}
.hero-card .tag { margin-bottom: 14px; }
.hero-card .statement { font-family: var(--serif); font-size: 19px; color: var(--ink); }
.hero-card .demo-choices { display: grid; gap: 8px; margin-top: 16px; }
.hero-card .demo-choices button {
  text-align: left; font-family: var(--serif); font-size: 16px;
  padding: 9px 13px; border-radius: 9px; border: 1px solid var(--line);
  background: var(--paper); cursor: pointer; color: var(--ink);
  transition: border-color .12s, background .12s;
}
.hero-card .demo-choices button:hover { border-color: var(--primary); }
.hero-card .demo-choices button.right { background: var(--ok-w); border-color: var(--ok); color: #0b6b48; }
.hero-card .demo-choices button.wrong { background: var(--no-w); border-color: var(--no); }

.cta-row { display: flex; gap: 12px; flex-wrap: wrap; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--sans); font-weight: 600; font-size: 15px;
  padding: 11px 18px; border-radius: 10px; border: 1px solid transparent;
  cursor: pointer; transition: transform .05s, background .12s, border-color .12s;
  text-decoration: none;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-d); text-decoration: none; }
.btn-ghost { background: var(--paper-2); color: var(--ink); border-color: var(--line); }
.btn-ghost:hover { border-color: var(--primary); color: var(--primary); text-decoration: none; }
.btn-ok { background: var(--ok); color: #fff; }
.btn-sm { padding: 7px 12px; font-size: 14px; border-radius: 8px; }
.btn[disabled] { opacity: .5; cursor: not-allowed; }

/* ---------- Filters / toolbar ---------- */
.toolbar {
  display: flex; gap: 10px; flex-wrap: wrap; align-items: center;
  margin: 8px 0 22px;
}
.field { display: flex; flex-direction: column; gap: 4px; }
.field label {
  font-family: var(--mono); font-size: 11px; letter-spacing: .08em;
  text-transform: uppercase; color: var(--ink-faint);
}
select, input[type="text"], input[type="number"], textarea {
  font-family: var(--sans); font-size: 15px; color: var(--ink);
  padding: 9px 11px; border: 1px solid var(--line); border-radius: 9px;
  background: var(--paper-2); min-width: 0;
}
select:focus, input:focus, textarea:focus {
  outline: 2px solid var(--primary-w); border-color: var(--primary);
}
.search { flex: 1 1 200px; }
.search input { width: 100%; }

/* ---------- Exercise cards ---------- */
.count { font-family: var(--mono); font-size: 13px; color: var(--ink-faint); margin: 0 0 14px; }
.cards { display: grid; gap: 14px; }
.card {
  background: var(--paper-2); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 18px 20px; position: relative;
}
.card-head {
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
  margin-bottom: 12px;
}
.card-head .title { font-weight: 600; font-size: 16px; letter-spacing: -.01em; margin-right: auto; }
.statement { font-family: var(--serif); font-size: 17px; line-height: 1.6; color: var(--ink); }

/* tags */
.tag {
  display: inline-flex; align-items: center; gap: 5px;
  font-family: var(--mono); font-size: 11px; letter-spacing: .04em;
  padding: 3px 8px; border-radius: 999px; border: 1px solid var(--line);
  color: var(--ink-soft); background: var(--paper); text-transform: uppercase;
  white-space: nowrap;
}
.tag.topic { color: var(--primary); border-color: #cfd3f6; background: var(--primary-w); }
.tag.easy   { color: #0b6b48; background: var(--ok-w); border-color: #bfe6d5; }
.tag.medium { color: #9a5a06; background: #FBF0DE; border-color: #f0dcb6; }
.tag.hard   { color: #a3282c; background: var(--no-w); border-color: #f2c9ca; }
.tag.grade  { }

/* answer area */
.answer-area { margin-top: 14px; padding-top: 14px; border-top: 1px dashed var(--line); }
.choices { display: grid; gap: 8px; }
.choice {
  display: flex; align-items: center; gap: 10px;
  font-family: var(--serif); font-size: 16px;
  padding: 10px 13px; border: 1px solid var(--line); border-radius: 10px;
  background: var(--paper); cursor: pointer;
}
.choice:hover { border-color: var(--primary); }
.choice.sel { border-color: var(--primary); background: var(--primary-w); }
.choice.correct { border-color: var(--ok); background: var(--ok-w); }
.choice.incorrect { border-color: var(--no); background: var(--no-w); }
.choice input { accent-color: var(--primary); }

.numeric-row { display: flex; gap: 10px; align-items: flex-end; flex-wrap: wrap; }

.feedback { margin-top: 12px; font-size: 15px; font-weight: 600; display: none; }
.feedback.show { display: block; }
.feedback.right { color: var(--ok); }
.feedback.wrong { color: var(--no); }

.solution {
  margin-top: 12px; padding: 14px 16px; border-radius: 10px;
  background: var(--primary-w); border: 1px solid #d8dbf8;
  font-family: var(--serif); font-size: 15.5px; line-height: 1.6;
  display: none;
}
.solution.show { display: block; }
.solution .lbl {
  font-family: var(--mono); font-size: 11px; letter-spacing: .1em; text-transform: uppercase;
  color: var(--primary); display: block; margin-bottom: 6px;
}
.author { font-family: var(--mono); font-size: 11px; color: var(--ink-faint); margin-top: 12px; }

/* ---------- Test mode ---------- */
.panel {
  background: var(--paper-2); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 26px; margin: 22px 0;
}
.panel h2 { margin: 0 0 6px; font-size: 22px; letter-spacing: -.02em; }
.panel .sub { color: var(--ink-soft); margin: 0 0 20px; }
.grid-2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 16px; }
.qnum {
  font-family: var(--mono); font-size: 12px; color: var(--primary);
  letter-spacing: .06em; margin-bottom: 8px;
}
.scorebar {
  display: flex; align-items: baseline; gap: 14px; flex-wrap: wrap;
  padding: 20px 24px; border-radius: var(--radius);
  background: var(--ink); color: #fff; margin-bottom: 20px;
}
.scorebar .big { font-size: 40px; font-weight: 700; letter-spacing: -.02em; }
.scorebar .pct { font-family: var(--mono); font-size: 15px; opacity: .8; }
.timer {
  font-family: var(--mono); font-size: 15px; padding: 7px 12px;
  border-radius: 8px; background: var(--primary-w); color: var(--primary);
}
.timer.low { background: var(--no-w); color: var(--no); }

/* ---------- Contribute ---------- */
.form-grid { display: grid; gap: 18px; }
.form-row { display: grid; gap: 6px; }
.form-row label { font-weight: 600; font-size: 14px; }
.form-row .hint { font-size: 13px; color: var(--ink-faint); }
.preview-box {
  border: 1px dashed var(--line); border-radius: 10px; padding: 16px;
  background: var(--paper); font-family: var(--serif); min-height: 44px;
}
.code-out {
  font-family: var(--mono); font-size: 13px; white-space: pre; overflow-x: auto;
  background: #12172a; color: #d6def5; padding: 16px; border-radius: 10px;
  line-height: 1.55;
}
.steps { counter-reset: s; display: grid; gap: 10px; padding: 0; margin: 0; list-style: none; }
.steps li { position: relative; padding-left: 38px; color: var(--ink-soft); }
.steps li::before {
  counter-increment: s; content: counter(s);
  position: absolute; left: 0; top: -1px;
  width: 26px; height: 26px; border-radius: 7px;
  background: var(--primary-w); color: var(--primary);
  font-family: var(--mono); font-size: 13px; font-weight: 700;
  display: grid; place-items: center;
}

/* ---------- misc ---------- */
.section-title {
  font-family: var(--mono); font-size: 12px; letter-spacing: .12em;
  text-transform: uppercase; color: var(--ink-faint);
  margin: 34px 0 14px; display: flex; align-items: center; gap: 12px;
}
.section-title::after { content: ""; flex: 1; height: 1px; background: var(--line); }

.empty {
  text-align: center; color: var(--ink-faint); padding: 50px 0;
  font-family: var(--serif); font-size: 17px;
}
.foot {
  border-top: 1px solid var(--line); margin-top: 60px; padding: 28px 0 40px;
  color: var(--ink-faint); font-size: 14px;
}
.foot code { font-family: var(--mono); background: var(--primary-w); color: var(--primary); padding: 1px 6px; border-radius: 5px; }

.hidden { display: none !important; }

/* KaTeX sizing tweak */
.katex { font-size: 1.04em; }

/* ---------- responsive ---------- */
@media (max-width: 760px) {
  .hero-grid { grid-template-columns: 1fr; }
  .site-head .wrap { gap: 12px; }
  .nav a { padding: 7px 9px; font-size: 14px; }
  .brand span.word { display: none; }
}

/* ---------- print (for tests) ---------- */
@media print {
  body { background: #fff; }
  .site-head, .toolbar, .no-print, .foot { display: none !important; }
  .panel, .card { box-shadow: none; border-color: #ccc; page-break-inside: avoid; }
  .solution { display: none !important; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; animation: none !important; }
}

/* ---------- auth / account additions (Supabase build) ---------- */
.auth-slot { display: flex; align-items: center; gap: 8px; margin-left: 4px; }
.auth-slot a {
  color: var(--ink-soft); font-weight: 500; font-size: 15px;
  padding: 7px 12px; border-radius: 8px;
}
.auth-slot a:hover { background: var(--primary-w); color: var(--primary); text-decoration: none; }
.role-badge {
  font-family: var(--mono); font-size: 10px; letter-spacing: .06em; text-transform: uppercase;
  padding: 3px 7px; border-radius: 999px;
  background: var(--ink); color: #fff;
}

.alert {
  font-size: 14px; padding: 11px 14px; border-radius: 10px;
  background: var(--primary-w); color: var(--primary-d); border: 1px solid #d8dbf8;
}
.alert-ok    { background: var(--ok-w); color: #0b6b48; border-color: #bfe6d5; }
.alert-error { background: var(--no-w); color: #a3282c; border-color: #f2c9ca; }